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Bob McDavitt's ideas for sailing weather around the South pacific

27 December 2015

Bob Blog 27 Dec 2015

WEATHERGRAM

YOTREPS

Issued 27 December 2015

 

Bob McDavitt's ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

Tropical Cyclones

There is a MJO (Madden Julian Oscillation) episode travelling into the Pacific Ocean – this increases the activity in the South Pacific Convergence Zone SPCZ and thus the chance of tropical cyclone formation during the next week or so.

 

See http://www.bom.gov.au/climate/mjo/#tabs=MJO-phase and read at this web site  more about the MJO—the main oscillation worth watching during the cyclone season, and note how strong and steady the parameter is at present in its march around its phase diagram.

 

Also, there are some equatorial westerly winds over Kiribati, not good for the local fishing fleet as these winds blow into the harbours that have been built for shelter from the normal SE wind. When these westerly winds blow steadily they increase the amount of spin available on the SPCZ.

 

Interestingly, there is a burst of stronger than normal NE trade winds in the northern Pacific: so this means there is not much of a gap between winds from opposing directions near the equator. In fact the computer models are analysing this as a cyclone near the equator at 177E --- I can't remember seeing such a weather ever before,  and because of the division by sine(latitude) in the wind equation there is not expected to be any curvature in the flow at the equator.

 

Check the MSL analysis as shown on windyty.com showing near-equatorial westerly winds over Kiribati and strong NE trade winds in the northern hemisphere, meeting in and twirling around a cyclone near the equator.

 

There are NO tropical cyclones around at present, however this chance of cyclogenesis is HIGH around the Pacific this week and there are two areas of interest at present---

 

One is 91P near 12.6°S 176.8°W and it has 7 analogues that went all over the place (go to http://www.tropicaltidbits.com/storminfo/  for the images).

 

Another, 92P, is closer to the Coral Sea and only has 4 analogues, and one of those went round the Coral Sea in a wide circle.

 

A third is further west near the active monsoonal trough over Australia near 16.0°S 134.6°E—this system is near Gulf of Carpentaria and had an opportunity to turn into a cyclone during the last week, but is still smouldering away. It has 5 analogues.

 

And there is another possible spot further west to the NW of Australia at 12.8°S 92.2°E

 

AT present there is no watch being kept on that pseudo-low near EQ 177E, however the GFS model indicates that this system may deepen into gales near Majuro by 31 Dec—take care.

 

SO this coming week may get busy in the tropics. A good period to stay put "on holiday" and see in the New Year.

 

Here for your singing enjoyment in Thursday night this week are the words of one of the lesser known verses of "Olde Lang Syne"

 

As written by Robbie Burns:

 

We twa hae paidl'd in the burn,

frae morning sun till dine;

But seas between us braid hae roar'd

sin' auld lang syne.

 

Translation:

 

We two have paddled in the stream,

from morning sun till dine†;

But seas between us broad have roared

since auld lang syne.

 

With this goes my greetings to you for the transition from 2015 to 2016.

 

Weekly rain maps for the tropics over the past two weeks,  as seen at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif,

show intense rain last week over northern Australia (from 99P) and eastern USA.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to increase in activity from Solomons to Samoa/Tonga.

There is an increasing chance of cyclogenesis this and next week. Take care.

 

STR= Sub-tropical Ridge

The "Sydney-Hobart-2015-race-trough" roared thru as expected last night, and although not really a sustained gale it managed to cause enough damage to take out several of the yachts including WILD OATS. It is being followed quickly by a HIGH that is expected to  travel slowly across central Tasman Sea this week and glide across central NZ from Thursday 31 Dec to Sat 2 Jan, with a zone of enhanced easterly winds on its northern side affecting northern NZ.

 

For NZ and Tasman Sea

A deep low with pressure below 990hPa near 40S 170W on Monday has come from the tropics and is moving slowly south. It is blocking a HIGH over NZ for Monday and part of Tuesday, and is expected to delay and weaken the eastwards progression of the "Sydney-Hobart 2015 race trough" (which is now in the central Tasman Sea forming a secondary low). The remains of this trough are now expected to cross southern and central NZ late Tuesday and during Wednesday.

 

>>>>>> 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts– Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom right to subscribe.

To unsubscribe,  send a reply email saying LEAVE.

 

 

20 December 2015

BOB Blog 20 Dec 2015

WEATHERGRAM

YOTREPS

Issued 20 December 2015

 

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

Summer Solstice is 17:48 NZDT on Tuesday 22 Dec.

It gets later in the year as we get closer to a leap year.

 

El Nino

This El Nino episode seems to be relaxing now.

 

Tropical Cyclones

Tropical cyclones are likely to form around the Australian coast during the next week or so, as picked by the Meteo France model

at http://www.meteo.nc/nouvelle-caledonie/cyclone/coin-des-experts

The weather models are not latching into anything specific at this stage,

and the most likely area is around the Gulf of Carpentaria and Queensland coast, so watch that area.

 

The Weekly rain maps show a continued easing of rain in the South Pacific.

They also show a concentration of rain around Indonesia and especially about the Philippines where a STATE OF CALAMITY has been declared. Half a metre of rain in a week.

See the Weekly rain signatures at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is rather weak and spread out mainly between 5 and 10S, with a finger stretching to Fiji.

There is expected to be a build-up of convection in the Coral Sea this week.

 

STR= Sub-tropical Ridge

High that is to NW of NZ on Monday should fade where it is as a front crosses the North Island on Tuesday.

Another HIGH is expected to cross Tasmania on Tuesday and then move towards central NZ for Friday/Saturday

(Christmas/Boxing days). The upper ridge is expected over NZ on 26/27, great for holiday weather, not so good for pasture.

 

For Sydney-Hobart 2015:

Strong hot northerly flow for a spinnaker start, nasty front on Sun 27th,

then there may be a SW wind change on back side of a developing low.

>>>>>>

 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website http://www.metbob.com for information on tailor-made

voyage forecasts– Feedback to bob@metbob.com. Tell anyone you like that

to subscribe they should email me.

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at

bottom right to subscribe.

To unsubscribe,  send a reply email saying LEAVE.

 

 

 

13 December 2015

Bob Blog 12 Dec 2015

WEATHERGRAM

YOTREPS

Issued 13 December 2015

Bob McDavitt's ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

A wonderful occasion for Planet Earth (and there is no Planet B) —190 nations agree to the COP21 in Paris in 13 Dec 2015.  It’s good to be alive during such an historic occasion.

This day may indeed go down in history as being a turning point.  Good way to start the festive season. See http://tinyurl.com/zrnkfty for a FAQ about this.

To mark this occasion there is a very large storm affecting Aleutian Islands (you can see it at  windyty.com).

 

El Nino

There are signs in the data that this El Nino may have peaked, or at least plateaued The NINO 3.4 index which measures the warmth of the sea sin the target area dropped last week, and the SOI index (based on barometers in Darwin and Tahiti) seems to be relaxing.

Latest data can be seen at http://www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekly .

 

Tropical Cyclones

The 28th numbered storm of the northwest Pacific’s tropical cyclone season developed this week rapidly east of the Philippines.

MELOR should be just south of Manila by Wednesday. It marks the first time in recorded history that a named storm has dotted the Philippines region every month of a calendar year, from Mekkhala in January to Melor now.

There is also BOHALE in the south Indian Ocean

 

The Weekly rain maps show an easing of rain in the South Pacific.

They also show an interesting stream of continuous moisture stream from China across the Pacific Ocean to Washington state in USA.

These rain maps may be seen at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is rather weak and spread out between 5 and 15S from 180 to French Polynesia.

Another branch of the SPCZ seems to be redeveloping in the northern Coral Sea.

SO it looks like a relatively quiet week in the tropics this week.

 

STR= Sub-tropical Ridge

High that is SE of Tonga tonight should continue travelling east along 30 to 35S.

High that is in the north Tasman Sea tonight is expected to fade away where it is by Wednesday.

Another HIGH is expected to cross Tasmania on Monday and then travel NE across the Tasman Sea during the week and northern NZ on weekend of 19/20 Dec.

 

Over NZ/Tasman:

Disturbed west to southwest flow.

>>>>>> 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts–

Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom right to subscribe.

To unsubscribe,  send a reply email saying LEAVE.

 

 

06 December 2015

BOB Blog 6 Dec 2015

WEATHERGRAM

YOTREPS

Issued 06 December 2015

 

Bob McDavitt's ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

The Chennai (India) floods death toll is over269, and the Cumbria (UK) flooding/wind death toll attributed to “Winter Storm Desmond” is 1, so far.

See  http://indianexpress.com/article/india/india-news-india/chennai-floods-rains-jayalalithaa-imd-reasons-rescue-news-updates/

 

The averaged isobar anomalies for November, as seen at  http://www.esrl.noaa.gov/psd/map/images/fnl/slp_30a.fnl.anim.html

show that the lowest lows have been in the Arctic, Southern Ocean near NZ,  the south Indian Ocean and off the Mexican west coast.

During the next month we can expect the low anomalies that are now near Mexico to drift south toward Tahiti.

 

Tropical Cyclones

There are currently no tropical cyclones around. However another tropical depression is being picked by GFS model to form near 5N 145W by mid-week.

There is expected to be an eastwards progression of active convection from the Indian Ocean into the Coral Sea region later this month,

and the likelihood of formation of a tropical cyclone in the week finishing 25 Dec may be seen from Meteo France at

http://www.meteo.nc/nouvelle- caledonie/cyclone/coin-des-experts (click on the three overlaid diagrams for the latest).

 

The Weekly rain maps, as seen at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif,

show rain concentrations in TUNI during the past two weeks, and a build up of rain in the Indian Ocean (and around Chennai).

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The main part of the SPCZ remains strong in activity and extends across Tuvalu/ Tokelau and Northern Cooks.

Another weaker convergence zone is lying along 15 to 17S from Vanuatu to Fiji.

 

STR= Sub-tropical Ridge

High is bending around south side of Tasmania tonight and expected to travel NE across the Tasman Sea this week and linger to north of NZ from Friday to Sunday.

 

Over NZ/Tasman:

Weakening front travelling off to north of NZ tonight followed by SW flow on Mon/Tues then a W to NW flow over the North Island for remainder of week. Next front is expected to travel onto North Island late Sunday 13 Dec, associated with a deepening low skirting southern NZ.

 

Travelling Tahiti to Marquesas.

The trough associated with the low that once was TC TUNI is expected to travel north across the Tuamotu region during next few days and weaken- This should bring SE/E winds between Tahiti and Marquesas until mid-week allowing a rare opportunity to sail this route.

 

Between Tropics and NZ:

The subtropical ridge is laying down a curtain of light winds along 25 to 30S.

Fronts over Northland are weak and seem to be arriving on late Sundays at present.

>>>>>> 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts– Feedback to bob@metbob.com.

Tell anyone you like that to subscribe they should email me.

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom right to subscribe.

To unsubscribe send a reply email saying LEAVE.

 

 

29 November 2015

Bob Blog 29 Nov

WEATHERGRAM

YOTREPS

Issued 29 November 2015

Bob McDavitt's ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

Tropical Cyclones

That tropical depression we were following last week has deepened into a Category 1 tropical cyclone TUNI.  Tropical cyclone TUNI is tonight moving toward the Niue area.

See Fiji Meteorological service at http://www.met.gov.fj/aifs_prods/65648.

html

Last week we also had Tropical Cyclone SANDRA making landfall on Baja California soon after Thanksgiving/Black Friday. –mainly as left over rain.

The origin of this cyclone was a Tehuantepecer (wind burst funneled by mountains)

(see https://en.wikipedia.org/wiki/Tehuantepecer) earlier in the week. 

See https://youtu.be/TvDT6gsTo8A for a windyty.com view of this metamorphic event.

 

The Weekly rain maps show rain concentrations in TUNI and SANDRA during

the past week.  

Weekly rain signatures are seen at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

SPCZ=South Pacific Convergence zone.

The main part of the SPCZ is strong in activity and extends from Tuvalu to TUNI (between Samoa and Niue) and has squally NW winds on its northern side. There is another branch along 15S across the Cooks and French Polynesia with N/NW winds on its northern side and SE winds on its southern side. 

 A low centre is expected to form on Monday UTC/Sunday local, near 15S 153W, close to the north side of Maupiti/Mopelia (Maupihaa) and this compact feature MAY develop into a cyclone over Tahiti area by mid-week.  The models are forecasting large swells around this feature. Brace accordingly.

 

STR= Sub-tropical Ridge

The STR is very strong this week with well-marked and slow-moving HIGHS.

A HIGH is crossing central NZ this evening and should travel slowly along 45 to 40S this week, further south than normal.

Another HIGH is expected to envelop the Aussie Bight mid-week and then move into the Tasman Sea on Friday.

 

Over NZ/Tasman:

Trough preceded by NW winds and with a southerly change reaching Sydney around local Wednesday morning and then Northland by late Friday, then fading away.

 

Travelling Tahiti to Marquesas. 

Convergence zone between Tahiti and Marquesas is too squally, and there is this tropical depression/possible cyclone forming on local Sunday. 

Best to stay put and tune in to local warnings and brace for strong winds/swell this week.

 

Between Tropics and NZ:

The lingering High makes travelling from New Caledonia to NZ OK, and should be OK when the wind/swells of TUNI ease around Fiji/Tonga.

>>>>>> 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts– Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom right to subscribe.

To unsubscribe,  send a reply email saying LEAVE.

 

 

22 November 2015

Bob Blog 22 Nov

WEATHERGRAM

YOTREPS

Issued 22 November 2015

 

Bob McDavitt's ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

The ICA seminar week in Opua (and there was one in Newcastle too) went well.

Thanks to all those sailors that attended my seminar on Friday afternoon.

It was great to meet with you and get your feedback—some of the stories you told were priceless and worthy of writing up.

 

El Nino:

The weekly value of Nino3.4 was measured last week to reach 3.0 C (above normal)

As seen at http://arstechnica.com/science/2015/11/el-nino-reaches-record-level-for-a-single-week-period/

This is a record reading, but it is the monthly NINO3.4 reading that counts, and also there are other ways of measuring El Nino.

Perhaps the broadest parameter is the Multivariate ENSO index which uses both atmospheric and oceanic data, as seen at

http://www.esrl.noaa.gov/psd/enso/mei/rank.html, is plateauing at 65.  It reached 66 in the 1997/98 and 1982/83 El Nino episodes.

The current El Nino episode is predicted to peak during the next three months and ease to neutral by mid-2016.

 

Tropical Cyclones:

Tropical cyclone features may be seen at http://tropic.ssec.wisc.edu/ Last week we had a set of twin tropical depressions near 170E.

The one in the southern hemisphere (93P)went west across northern Vanuatu and into the Coral Sea.

The one in the northern hemisphere (95W) also went west, taking it towards the Philippines – it now has the name In-Fa and is expected to re-curve and stay out at sea.

In the south Indian Ocean TC ANNABELLE is expected to travel south near 70E.

And in the warmer than normal seas off Mexico’s west coast tropical depression RICK is expected to travel north near 120W.

The Weekly rain maps show convection traveling southwards from the equator into the southern Indian Ocean and into the  South Pacific Ocean.

These can be seen at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The main part of the SPCZ is strong in activity and extends from Solomon Islands to Samoa, with a dip south towards Fiji.

A tropical LOW is likely to form on this zone north of Fiji by mid-week and then travel across the Samoa/Northern Tonga region by end of the week, very likely bringing squally rain and possibly bring strong winds. This may be a hazardous feature so if you are in the area keep close tabs on its progress, and take adequate precautions in advance.

 

STR= Sub-tropical Ridge

The STR is very strong this week. A HIGH is expected to travel across northern NZ on Monday and then linger to east of North island for the remainder of November and into early December. Fronts crossing the Tasman Sea are likely to be diverted by this strong High so that they travel onto to the South Island.

 

Over NZ/Tasman:

Disturbed west to NW flow south of Northland with occasional fronts.

 

Travelling Tahiti to Marquesas.

Easterly winds are expected to turn and be from NE by end of this week, and maybe NW next week. Active convergence zone with squally showers is expected to lie in-between Tahiti and Marquesas by end of this week.

 

Between Tropics and NZ:

The HIGH lingering to east of North Island from this week into around mid- next-week gives a great opportunity for sailing to NZ from Tonga/Fiji/New Caledonia.

>>>>>> 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts– Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom right to subscribe.

To unsubscribe send a reply email saying LEAVE.

15 November 2015

Bob Blog 15 Nov

WEATHERGRAM

YOTREPS

Issued 15 November 2015

Bob McDavitt's ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

Equatorial Twin tropical lows

There are no tropical cyclones at present, but two tropical lows are twinning near 170E.

In the north is 95W and this is expected to peel off to the west and then recurve before reaching Philippines.

And 93P in the south should travel south across Vanuatu this week then turn into a trough that is expected to reach Fiji to Minerva by Friday and maybe Tonga on Saturday. 

 

Weekly rain maps at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif show build ups of convection around India and in the South Pacific to north of Fiji.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The main part of the SPCZ is expected to linger from PNG to Vanuatu and from Tuvalu to Samoa.  There is also likely to be some squally rain with the low /trough associated with 93P.

 

STR= Sub-tropical Ridge

The STR is stronger this week than last week with large slow-moving highs.

  One to NE of NZ on Sunday is expected to travel along 30S. Another is crossing Tasmania on Sunday night local and cross the Tasman Sea on Monday Tuesday, then NZ on Wednesday, and off to the NE of NZ from Thursday.

 

Over NZ/Tasman:

A weakening front is expected to cross northern NZ on Monday followed by a SW flow on Tuesday. Next front is expected to cross northern NZ on Friday followed by a weak ridge on Saturday and another front on Sunday 22 Nov. 

 

Travelling Tahiti to Marquesas. 

Easterly winds.   Active convergence zone with squally showers lies in-between.  

 

Between Tropics and NZ:

OK for departing from Fiji/Tonga early in the week, so long as you arrange arrival in NZ to avoid the front and SW winds expected on 22/23 Nov. 

After around Tuesday, take into account the track of that tropical low over Vanuatu. 

Its trough is expected to reach Fiji to Minerva by Friday, and the NE winds and squally showers that precede this trough may reach Fiji to Minerva by late Thursday.

>>>>>> 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts– Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom right to subscribe.

To unsubscribe, send a reply email saying LEAVE.

 

 

08 November 2015

BOB BLOG 8 Nov

WEATHERGRAM

YOTREPS

Issued 8 November 2015

Bob McDavitt's ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

El Nino is strong and increasing and about to get as strong as it was in 1997/8

 

This can be seen by looking at the sea surface temperatures for the NINO3.4 area in eastern equatorial Pacific, at http://farmonlineweather.com.

au/climate/indicator_enso.jsp?c=nino34&p=monthly.  There is now ample excess energy stored in the ocean, ready to be released into the

atmosphere by “teleconnections” to activate storms and prolong droughts.

 

 

Merging Lows to NE of NZ last week

The Low that crossed NZ last Wednesday (its frontal rain arrived in time to greet the All blacks as they arrived at Auckland Airport , and its

southerly gale greeted HRH The Prince of Wales in Wellington all of Wednesday) danced with and then was taken over by a smaller  smaller low

to the north.  This is what meteorologists call the Fujiwhara effect, see https://en.wikipedia.org/wiki/Fujiwhara_effect.   I wasn’t able to

capture the satellite imagery, but here’s the Windyty animation--- but I suspect the models haven’t captured the event as it really occurred. See

https://www.youtube.com/watch?v=TdQOmaYV508&feature=youtu.be

 

TROPICAL TOPICS

Following close of the heels of CHAPALA from last week, tonight we have MEGH heading for Yemen. See  http://www.tropicaltidbits.com/storminfo/

 

Weekly rain maps form http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif show that the main part of the convection in the Indian Ocean has spread east in the past week.

This eastward trend ( MJO cycle) seems to be on track to move across northern Australia by end of November and into Coral Sea area maybe by

mid-December. SO the risk of tropical cyclone formation in the south Pacific is expected to remain low for the next few weeks according to

that observation.

The maps also show the South Pacific convergence zone has spread out since last week and become more diffuse but covers a wider area.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The main part of the SPCZ is expected to linger from north of Vanuatu to Samoa with a branch towards French Polynesia. However, just as it did

last week, some of its convection is likely to drift south—moving onto northern Fiji especially from Thursday to Sunday, and maybe northern

Vanuatu as well.

 

STR= Sub-tropical Ridge

The strong HIGH that arrived in the South Pacific last week is expected to continue moving east this week along 40S well to the east of NZ. 

Central Australia is now so hot that the HIGHS are shunning it (hot air=low pressure) and thus travelling across the Australian Bight and south

of Tasmania. The next incoming HIGH is expected to be doing this by mid-week and then travel around southern NZ on Friday. It is also expected to

intensify on Friday, thus producing a squash zone of SE winds on its northeastern side= a SE wind burst. This squash zone should spread north

on Saturday and Sunday—as far north as 28S.

 

Over NZ/Tasman:

A weakening front is expected to cross the North Island on Monday followed by a SW flow from Tuesday to Thursday and a SE wind burst early

on Friday. The next front in the Tasman Sea is expected to deepen into a LOW on Sun 15 Nov that crosses North Island on Mon 16 Nov.

 

Travelling Tahiti to Marquesas.

Easterly winds and minor convergence zones.

 

The Island Cruising Association is holding the All Points rally to Opua and the Downunder rally from Noumea to Newcastle.

Between Tropics and NZ: for the All Points Rally, ending in Opua:

It is the time of the year that analysis paralysis sets in at the Minerva Yacht club.

The SE wind is expected to return to Minerva for Sat/Sun 14/15, otherwise just light SW/SSW/S winds there this week, and outlook is for light NE/E

winds there for much of next week.

Its difficult to decide when to go when there are either SW winds or large wind holes partly affecting the way from Tonga to NZ.  Well at this

stage next week may have even larger wind “holes” so perhaps some of the second class patterns of this week should be chosen rather than waiting

too long – I can produce some waypoints for you to guide you around the holes and SW zones, but they will take longer than going direct.

The only lot of strong winds that I can see this week is to do with that squash zone over NE NZ on Friday 13 – moving off to the NE on Sat 14—and

it is easy enough to avoid by going well enough west around it.

Looking ahead, there are likely to be strong N/NW winds on Mon 16 Nov with that passing Low, and these may extend north of NZ to around 30S. At

least they are tailwinds for incoming yachts.

 

Between Tropics and Australia

For the Downunder Rally (Noumea to Newcastle)

I’m informed that 75% have arrived and 25% are in transit.

Avoid arriving in Newcastle when a front /low passes by the area on late 12/13/14 Nov and again on 17/18 Nov.

>>>>>>

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts– Feedback to bob@metbob.com. Tell anyone you like that to

subscribe they should email me.

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom right to subscribe.

To unsubscribe send a reply email saying LEAVE.

 

01 November 2015

BOB Blog 1 Nov 2015

WEATHERGRAM

YOTREPS

Issued 1 November 2015

Bob McDavitt's ideas for sailing around the South Pacific.

 

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

Tropical cyclone genesis and occurrence: A weekly treasure:

The Meteo France weather Office in Noumea have started a page on their web site which translates the latest phase of the MJO (Madden Julian Oscillation= a quasi-cycle that travels from the Indian Ocean across Northern Australia to western pacific around once every 3 to 6 weeks, encouraging extra convection) into maps showing the probability of occurrence or genesis of tropical cyclones. These can be found at http://www.meteo.nc/cyclone/coin-des-experts (then click on the example graphics to get the latest).

These maps show that the MJO is active in the Indian Ocean at present—and this implies that it may get to the western South Pacific late this month or early December.

I suppose this means that there is no immediate hurry for departing the tropical South Pacific. However If your marine insurance becomes void in the cyclone season (and many Insurance Companies define that as from 1 November for South Pacific) then your financial risk has risen overnight.

 

TROPICAL TOPICS

In tune with the MJO, there is just one active tropical cyclone at present and it’s near the horn of Africa. CHAPALA, heading for Yemen. See http://www.tropicaltidbits.com/storminfo/

 

The Weekly rain maps, as seen at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif,

show steady convection over western part of Indian Ocean, and a weakening over the whole Pacific Ocean.

 

WEATHER ZONES

 

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to have a reasonably quiet week mainly near Solomons to Tuvalu and Tokelau, with scattered convection over Southern cooks/French Polynesia. There may also be some shower activity for Wallis and Futuna.

 

STR= Sub-tropical Ridge

The axis of the STR is strong along 30S from north of NZ to south of Pitcairn Island. Strong enough to provide a zone of light winds for yachts heading to NZ from the tropics. Nothing much can be done about this except for motoring in light winds. The pattern seems to be in place until at least mid-month.

The HIGH that is in the Australian Bight tonight should cross south of Tasmania on Tuesday and then travel NE across the Tasman Sea and stall over northern NZ from Sat to Tues 10th and then be replaced with another High keeping a ridge over or to north of northern NZ from Wed 11 to Sat 14 Nov.

 

Over NZ/Tasman:

The front moving NE over southern NZ on Monday is expected to receive a developing low from Australia on Tuesday and deepen this over central NZ on Wednesday so that the low hovers to east of the North Island from Wed to Friday (an olde man southerly), and the lingers off to NE of North Island from Sat to Mon 9 Nov (cut off upper low).

There are likely to be SW winds partly on the way between NZ and Tonga from Thursday to Sat 9 Nov.

 

Travelling Tahiti to Marquesas.

Easterly winds and minor convergence zones. May be NE winds locally over Tahiti on local Sunday/Monday.

 

Travelling Tahiti to Tonga:

The SPCZ should stay north over most of this route and is weak over Tahiti.

No squash zones this week. A trough is expected to travel from Tonga to Niue this weekend, Sat/Sun 7/8 Nov UTC, bringing light variable winds, maybe some SW winds and a few showers.

 

The Island Cruising Association is holding the All Points rally to Opua and the Downunder rally from Noumea to Newcastle.

Between Tropics and NZ: for the All Points Rally, ending in Opua:

A weak trough is expected to form over the Minerva area on local Thursday and travel to Tongatapu by Friday night, with variable light winds, and followed by a period of SW/S winds--- This isn't a major problem but does take the edge off the comfort of any departures from Tonga on Thursday and Friday.

Departures from Tonga (and sometimes Fiji) to NZ this week have some S/SW winds to divert around, especially from Thursday to Saturday—and this can be done by going far enough WEST before the southerlies and encountered, but does slow and lengthen the voyage.

Departures from Fiji and New Caledonia have that subtropical ridge axis to cross—a zone of no wind near 28 to 30S.

AT this stage, looking 5 days plus ahead, it seems that there are no dates to avoid for arrival in NZ, but onshore easterly wind are expected over NE NZ on Tuesday 10 November so maybe avoid that day.

 

Between Tropics and Australia

For the Downunder Rally (Noumea to Newcastle) Hmmm. A Low from the heat of the interior of Australia is expected to travel east along 35S across New South Wales and into the Tasman Sea on Thursday bringing a SW change into Newcastle on Friday 6 Nov. This may not be a gale—but the rain (mainly on Wednesday) should be squally.

The associated trough should weaken quickly but linger along 30S.

Departures from Noumea this week before Thursday are likely to just encounter some of that left-over trough near 30S. On Monday 9 Nov there may be STRONG northerly winds and squally rain near 30S – avoid.

>>>>>>

 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts– Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom right to subscribe.

To unsubscribe send a reply email saying LEAVE.

 

25 October 2015

BOB Blog 25 Oct

Bob Blog 25 Oct

WEATHERGRAM

YOTREPS

Issued 25 October 2015

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

Tropical Note: A weekly treasure:

The Bureau of Meteorology Australia weekly tropical note at http://www.bom.gov.au/climate/tropical-note/ is updated every Tuesday and carries comments on the trends in the MJO oscillation.

Even if you are limited to only email via satphone or shortwave, you can read this note by sending an email to query@sailmail.com, no subject needed, saying SEND http://www.bom.gov.au/climate/tropical-note/

MJO stands for the Madden-Julian Oscillation, an increase in tropical convection that tends to travel eastwards from the Indian Ocean to the western parts of the South Pacific. It helps trigger the formation of Tropical cyclones. The MJO has been weak/ undetectable for many weeks, but is now starting to appear in the Indian Ocean. It usually takes around a month for it to track from there to South Pacific, so having an MJO in the Indian Ocean reduces the risk of a tropical cyclone forming in the South Pacific.

 

TROPICAL TOPICS

PATRICIA has come and gone, and was category 5 for a while off the west Mexican coast. OLAF is still in the mid North Pacific since last week.

And the many “Invest” areas in the Indian Ocean is associated with the MJO.

The Weekly rain maps at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif show increasing convection over western part of Indian Ocean, and a weakening of convection in the South Pacific.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to have a reasonably quiet week near Tuvalu and Tokelau, with scattered convection over Southern cooks/French Polynesia.

 

STR= Sub-tropical Ridge

The STR is weakening in the Tasman Sea area but is expected to stay strong to east of 180 this week. The squash zone of enhanced SE winds that is tonight between Niue and Austral Islands is expected to weaken from tomorrow.

High in northern Tasman Sea tonight is expected to cross northern NZ on over Tasmania tonight is expected to travel NE across Tasman Sea and cross northern NZ on Tuesday and then weaken.

Next HIGH is further south and is expected to travel around south end of Tasmania on Friday, and then slowly across northern NZ on Sun–Wed 1 to 4 Nov.

 

Over NZ/Tasman:

ACTIVE FRONT from Sydney to South Island on Monday and from off Coffs to central NZ on Tuesday is expected to deepen into a LOW between Lord Howe Island and North Island on Wednesday and this low is then expected to travel east across the North Island on Thursday with strong to gale SW winds and large swells on its western side. Avoid.

 

Travelling Tahiti to Marquesas.

It seems that several yachts are thinking of spending the cyclone season in Marquesas rather than Tahiti—seems sensible since this season is likely to be like 82/83 (14 cyclones, 10 in the Cook Islands/French Polynesia/Pitcairn area) or 97/98 (16 cyclones, 8 in French Polynesia).

The good news this week is that weather pattern is looking Ok for voyages from Tahiti and Marquesas for departures on local Monday or Tuesday, maybe Wednesday, with light winds between Tahiti and Tuamotu for motoring,  and then easterly winds between Tuamotu and Marquesas. This is a brief window, associated with a weak trough on the weak SPCZ over the Tahiti area next few days, and these windows are rare so go for it by Tuesday.

 

Travelling Tahiti to Tonga:

The SPCZ should stay north over most of this route and is weak over Tahiti, and the squash zone around Cooks Islands/Tahiti tonight should ease by local Tuesday, then there is a reasonable opportunity for departure. There are likely to be a few convergence zones along this route with some light winds.

 

The Island Cruising Association is holding the All Points rally to Opua and the Downunder rally from Noumea to Newcastle.

 

Between Tropics and NZ:

For the All Points Rally, ending in Opua:

A departure early this week should be Ok. It is likely to have a period of SW winds between 25 and 30 S with 2 to 3 metre swells on Thursday and Friday thanks to that NZ Low.

If you are heading for NZ from New Caledonia/Fiji or Tonga, then the main deciding pointers are the fronts crossing northern NZ. After that Low over NZ on Thursday 29 Oct, there is a slow-moving HIGH from Sun 1 to Wed

4 Nov and then a strong NW wind is expected (at this stage) over northern NZ around Thu 5 Nov, followed by a few days of westerly winds. Since there is nothing significant happening in-between the islands and NZ if you arrange a departure this week that avoids arriving in NZ on Thu 5 Nov,  then that should work—but seek updates as well as things keep changing.

 

Between Tropics and Australia

For the Downunder Rally (Noumea to Newcastle) A departure early this week should be Ok. It is likely to reach just moderate southerly winds and 2 m swells near 26S from that “Wed 28 Low”

between Lord Howe and NZ.

Newcastle is expected to have its next dose of strong winds on Monday 2 Nov, and since this voyage may usually take around 6-7 days, depart on Monday this week to try and arrive before these strong winds, or wait for an opportunity later this week, maybe Thursday onwards.

>>>>>>

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website http://www.metbob.com for information on tailor-made voyage forecasts– Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom right to subscribe.

To unsubscribe send a reply email saying LEAVE.

 

 

 

 

18 October 2015

Bob Blog 18 0ct 2015

WEATHERGRAM

YOTREPS

Issued 18 October 2015

Bob McDavitt's ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

Bureau of Meteorology Australia have now issued their 1015-16 Tropical cyclone season outlook and they are going for a less active season.

See http://www.bom.gov.au/climate/ahead/tc.shtml

This ties in with the NIWA, MetService NZ and Fiji Met Service outlooks given here last week going for a more active season in our part of the South Pacific (east of 160E). Basically the activity is shifted eastwards by the El Nino episode we are having.

Now, since a lot of tropical Cyclone and Depression activity starts along the South Pacific Convergence Zone, it’s expected average position should show where most of this season’s tropical Cyclones are likely to form.

NIWA have published an  image showing this earlier this month as part of their Island Climate Update at

http://www.niwa.co.nz/island-climate-update-181-october-2015

and it shows the expected average position (green line) from now until December for the SPCZ from an ensemble of global climate models. The red line is the climate average for this time of year, showing how far north (and east) is this seasonal shift. In the image, brighter shades of purple show the expected wetter areas—showing that western Solomon Islands to Tonga are NOT expected to have much of a wet season this year.

Since many insurance companies define the South Pacific Cyclone Season as being from 1 November to 30 April (and remove their cover accordingly), a lot of yachts are likely to leave the warmth of Tonga /Fiji/New Caledonia and head for Australia/ New Zealand. (Small note: Minerva reef at 24S is technically OUT of the tropics, so even if your insurance cover may be void from 1 Nov in Tonga, it remains valid in Minerva forever!).

The Island Cruising Association is especially geared up to help those wishing to spend the cyclone season in NZ, and organise an ALL POINTS RALLY for this. It’s free (thanks to the sponsors) and helps yachts with weather info, resources and planning tools to try and make the passage as easy as possible. In Opua participants are offered a week of fun, entertainment and seminars, starting 16 Nov. It’s a bit late now, but if you want to sign up go to http://www.islandcruising.co.nz/?page_id=717

Australians do not want to be outdone and this year have started their own Noumea to Newcastle DOWNUNDER Cruisers Rally – an evolution of their Port2Port P2P Rally –and also an ICA event. Some have left already. Their Noumea Departure party is this Friday 23 Oct, and their week of fun and culture starts 15 Nov. If you want to know more about this then go to http://www.downunderrally.com/ and an entry form is at http://www.

islandcruising.co.nz/?page_id=3097.  I recommend the passage planning page by Rod Waterhouse at

http://www.downunderrally.com/#!passage-planning--weather-/c92m

To help these rallies I'll concentrate my Weathergram between now and mid- November on these events.

 

TROPICAL TOPICS

KOOPU has brought damaging wind and rain to Philippines and is now slowly working its way northwards along its west coast, and CHAMPI has also turned northwards already so may stay out at sea. While OLAF is this week’s cyclone for the mid North pacific.

During the past week we had an interesting tropical depression form north of Fiji, it went west then south and on Friday was on the verge of being named a tropical cyclone but didn't quite make the grade. It needs gale winds near its centre for at least half a circle.

It has made an interesting jump to the west on Sunday morning local time, as seen at the web site from Fiji Met Service at http://www.met.gov.fj/aifs_prods/65661.

html.

The Weekly rain maps at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif show strong rainfall near the Philippines from KOOPU and further east in CHAMPI, and also around Tuvalu.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ has lost some convective energy now that it has been take away by that tropical depression near Fiji. What is left is expected to have a reasonably quiet week neat Tuvalu and Samoa, with scattered convection over Southern cooks/French Polynesia,

 

STR= Sub-tropical Ridge

The STR is STRONG along around 30 to 35S, and has been creating squash zones of enhanced SE winds and/or southerly swell following fronts and on the northern side of the High cells as they migrate east.

High over Tasmania tonight is expected to travel NE across Tasman Sea and cross northern NZ on Tuesday and then migrate eastwards with a squash zone – mainly of 3m swells- on its north side particularly affecting the Tahiti to Niue route from Thursday to Saturday.

Another HIGH over Tasmania on Thursday is expected to reach northern NZ by Sunday 25 Oct, and then travel east and bring another squash zone to the Tahiti to Niue route next week.

 

Travelling Tahiti to Tonga:

A zone of 3m+ swells from the Southern Ocean affects southern part of this route on Tuesday and Wednesday UTC. Another zone of 3m+ swell, along with some strong SE winds, from a squash zone affects this route from Thursday to Saturday.

 

Between Tropics and NZ:

 

For the All Points Rally:

Early this week there are light winds near Fiji and rough seas off the south of New Caledonia—that may delay some starters.

If you are heading for NZ from New Caledonia/Fiji or Tonga, then the main deciding pointers are the fronts crossing northern NZ. There’s one this week on Thu/Fri 22/23 Oct, and its followed by a period of southerly quarter winds on Friday/Saturday—you should be able to cope with those by going W in southerly winds, SW in SE winds and SE in SW winds.

 

Between Tropics and Australia

For the Downunder Rally (Noumea to Newcastle) Some rough seas just south of New Caledonia and start of Tuesday so departure after that is more comfortable.

A southerly buster is forecast to reach Newcastle around midnight Wednesday and these southerlies may reach as far north as 25S on Wed/Thu maybe Friday, but should be able to be handled with appropriate waypoint diversions.

Strengthening northerly winds are likely offshore Newcastle on Monday and Tuesday 25-27 Oct and then a heat trough is expected to cross Newcastle on Wed 28 Oct possibly with thunderstorms.

AT this stage a Wednesday departure seems to be the most comfortable of the week.

>>>>>> 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts– Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom right to subscribe.

To unsubscribe send a reply email saying LEAVE.

 

 

11 October 2015

BOB BLOG 11 Oct

WEATHERGRAM

YOTREPS

Issued 11 October 2015

Bob McDavitt's ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

A comparison of the Sea surface temperature anomaly map at start of October of this year with 1997 – as shown by NOAA may be  seen in the LA

Times:  LA Times link:

http://www.latimes.com/local/lanow/la-me-ln-massive-el-nino-is-now-too-

big-to-fail-scientist-says-20151009-story.html

Notice how this year there is an extension of cooler than normal sea from the Papua New Guinea to the Fiji Tonga area—whereas back in 1997 this

zone was warmer than normal.   It is reasonable to postulate (but hard to

prove in advance) that this finger of coolness may help reduce the risk of cyclone formation or cyclone support. A Mercator projection view of this cool blue finger-zone of reduced risk may be seen at  http://www.

ospo.noaa.gov/data/sst/anomaly/2015/anomp.10.8.2015.gif

 

Now that 1997/1998  South Pacific Cyclone season was the most active and longest on record with 16 named cyclones in the South Pacific basin between early October and early May. 

8 of these 16 affected French Polynesia Cook Islands

1982/83 was also an extreme El Nino year with 14 named cyclones:

10 of these 14 were in the French Polynesia/ Cook Islands area.

To compare El Nino seasons a good parameter to use is the NINO3.4, (based the sea surface temperature anomalies in the target area) and a long term graph of this may be found at https://besfeg.wordpress.

com/2015/05/27/will-a-big-el-nino-spell-doom-for-tropical-forests/

Data (up to Sep 2015) is from http://www.cpc.ncep.noaa.

gov/data/indices/sstoi.indices

 

The September 2015 value of the NINO3.4 anomaly was 2.28 compared with 1.

39 in September 198 and 2.21 in September 1997, so at first glance this is a match –and we can postulate (even if it may be difficult to prove in

advance) that the French Polynesia/Cook Islands area are at a higher risk than normal of being affected by tropical cyclones during this season.

However this is just one parameter and, as we can see for the opening image, there is more happening even in the SST anomaly map than just the

NINO3.4

 

Some web sites such as Wikipedia think that this cyclone season has already started, for they start their count from 1 July and RAQUEL formed

30 June, left the basin area and then re-entered on 4 July and faded the

next day.   However, I think that the vernal equinox, when the overhead

suns shifts into the southern Hemisphere, is a more logical date to start the count rather than from 1 July.

 

TROPICAL TOPICS

There is just one named storm in the tropics at present – NORA near Hawaii (again).

The Weekly rain maps  from http://trmm.gsfc.nasa.

gov/trmm_rain/Events/big_global_accumlation.gif show that convective activity has jumped in the past week from the Intertropical Convergence zone to the South Pacific Convergence zone.

This increased activity in the SPCZ coincided with a period of near equatorial westerly winds.

The tropical low on the north side of the equator near 10N 150E is expected to deepen further and may form a Tropical Cyclone.  The Low east of Solomon Islands is expected to weaken and move off to the SE.  SO the “twinning” mechanism seems to have missed working this time.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

There is a lot of activity between Eq. and 15S from 160E to 180 at present and this moisture is expected to feed along the SPCZ that extends

from eastern Solomon Islands to the Fiji area.   SO squally wind and rain

is likely to visit parts of Fiji around mid-week. The GFS model has a tropical low with this on Wednesday UTC but the more reliable EC model at www.tinyurl.com/ecaus has the low further west and from Sat 17 Oct—so the models are flip-flopping and the area is worth watching with care.

Strong SE winds on the south side of the SPCZ are expected to affect Fiji area until Wednesday, and then this zone of strong winds should shift south to around 25S and stay there for a few days.  The strong SE winds that have been affecting Vanuatu are expected to ease from Wednesday.

 

Further east a convergence zone of the north side of a passing front is expected to pass across French Polynesia over the next few days changing the wind direction over the south half of the area.

 

STR= Sub-tropical Ridge

High in the Northern Tasman sea on Sunday (HIGH1) is expected to stay there and fade away on Tuesday/Wednesday as a cold front travels north into it and across North Island and also fades. 

A new High, HIGH2,  following that cold front,  is expected to dominate the South Tasman Sea  by Wednesday and travel across Northern NZ on Friday to Saturday.

This pattern is expected to repeat with a front fading over northern NZ on Sunday 18 Oct and another High, HIGH3 form Monday 19 to Friday 23Oct.

HIGH2 is intense  enough to have a squash zone of strong SE winds on its northern side so that over New Caledonia, SE winds have eased over the weekend but are now expected to increase again from late Tuesday until Friday. And over Tonga, strong SE winds are expected from Wednesday to Saturday, and this squash zone should spread east to affect Niue/Southern Cooks/Society Islands.

 

Travelling Tahiti to Tonga or from Fiji to anywhere:

A difficult week, affected by SPCZ and a squash zone, so maybe stay put.

 

Between Tropics and NZ:

HIGHS 1, 2 and 3 dominate northern NZ over next two weeks, so winds are not strong, but the E/SE winds on the north side of the STR mean that trips from Tonga and New Caledonia have to start setting off with a leg to the SW and then turn to NZ around about 30S.

The weak “replacement” fronts between the highs on 13/14 Oct and 17/18 Oct and have NW winds ahead of them that offer good sailing breeze to northern NZ, but are followed by SW winds. 

As for southern NZ --- well, here be dragons:  vigorous disturbed westerly winds dominate proceedings.

>>>>>> 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts– Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom right to subscribe.

To unsubscribe send a reply email saying LEAVE.

 

 

04 October 2015

Bob Blog

WEATHERGRAM

YOTREPS

Issued 04 October 2015

Bob McDavitt's ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

Tropics to NZ: - Strategy

  This is the time of year that yachts are staging themselves in Tonga (or Fiji or New Caledonia) and waiting for the right weather pattern for sailing to NZ or Australia.

 

In deciding upon a departure date, the first factor to consider is the local weather:  the South Pacific Convergence Zone SPCZ sometimes brings squalls, but is expected to stay north from Solomons to Tuvalu to Tokelau /Samoa to Northern Cooks this week.  It might visit Wallis and Futuna during middle of this week.  

 

Some like to use Minerva reef as an extra staging post since it is 1.5 days sail south of Tonga, and just out of the tropics (so marine insurance that is void in the tropics may work in Minerva).  But it only shelters you from the waves (so long as they don’t topple over the reef) and not from the wind. 

 

The second factor to watch are the HIGHS that travel along the Subtopic ridge STR, that zone between the trade winds of the tropics and the disturbed westerlies of the roaring 40s.  There is a HIGH in the Tasman Sea at present and it is expected to intensify on Tuesday, producing a SQUASH ZONE of enhanced trade winds on its northern side stretching from Coral Sea to Tonga.  During Wednesday this High is expected to weaken and the squash zone should retreat to the Coral Sea area by Thursday. Another HIGH is expected to travel from 45S over South Tasman Sea on Thursday to 30S over Northern Tasman Sea on Tue 13 Oct – this High is not expected to be intense enough to have a squash zone, but the strong SE winds are expected to remain in the Coral Sea. 

 

The third factor is to avoid strong southerly winds and heavy swells during the trip.  Good news is there isn’t much to report this week. There is a front moving off to east of NZ tonight followed by a SW/S flow, but it isn’t strong.  It may bring some SW swells from Southern Ocean to the area north of NZ but these have a lengthening period are reasonably flat. 

 

And you should try and time your trip so that it does not reach NZ with an active weather feature.  Since these voyages may take 8 to 10 days, the weather outlook that far out is not reliable on any weather models and things will change in the real world during the voyage.  However with resources such as windyty.com now available we can at least get an idea of the winds around NZ a week ahead.  Today’s data shows that a FRONT is likely to cross Northland around wed/Thu 14/15 Oct followed by a burst of southerly winds extending north of NZ to at least 30S.  SO avoid arriving in NZ then, and that means don’t depart Tonga late this week, unless you can beat that front or don’t mind encountering it.

  

This is the season that we sometimes get a procession of fronts travelling across Northern New Zealand, maybe 4 or 5 days apart. Not this week. When this pattern sets in, it may be necessary to deliberately time you departure to encounter one of these fronts near 30S (where they are usually weak) (and then dash for NZ in the SW winds that follow.  This strategy may require you to travel as far west as 170E before encountering the front, and that adds days to the journey if it is starting form Tonga.

 

A useful resource is www.yit.co.nz.  Patricia and David from Gulf Harbour Radio provide a method where by your position can be plotted on the web, and also provide daily weather updates via shortwave radio. You need to first register on this web site with your boat and crew details and then you simply email (send@yit.co.nz) or radio (call in to the sked) in your position and conditions in preferably each day.  These reports help me (and your loved ones) keep track of your progress.

David checks these reports and does a weather sked, Monday thru Saturday (NZ date), on 8752 at 1915UTC to make sure the models reflect your actual conditions.  He does a round-up of the weather in each island group, including passage weather, at 1930UTC. That’s 7.30am depending on your time zone.

 

The High seas forecast SUBTROPICS  is the official forecast for this area issued by the marine team at MetService is broadcast by Taupo Maritime Radio ZLM at 0903UTC on 6224 and 12356kHz , and 1003UTC on 9297 and 16531kHZ, then again on 2103UTC on 6224 and 12356kHz , and at 2203UTC on 9297 and 16531kHz.  If you have access to email on board then the text of this bulletin is available by sending an email to query@saildocs.com, no subject needed, with message SEND http://weather.noaa.gov/pub/data/raw/fq/fqps43.nzkl..txt

Or remember to email or TXT your position report to me at bob@metbob.com 64277762212

 

TROPICAL TOPICS From http://tropic.ssec.wisc.edu/

Tropical storm OHO is near Hawaii, Hurricane JOAQUIN is in the Atlantic, Typhoon MUJIGAE in in the China Sea, and Tropical Storm CHOI-WAN is in the NW Pacific 

The weekly rain maps as seen at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif show that rainfall in the South Pacific is confined to the SPCZ 

>>>>>> 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts

– Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom right to subscribe.

To unsubscribe send a reply email saying LEAVE.

27 September 2015

Bobgram issued 27 Nov 2015

WEATHERGRAM

YOTREPS

Issued 27 September 2015

Bob McDavitt's ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

Note that NZ has switched to Daylight Time today .

 

There is a full tide in the middle of the  night when we have the  last quarter moon.  Well, the one after  the equinox (and that’s around 5 Oct this year) normally triggers a spawning of the Palolo coral warm. They drop off their worm-tails or pods; jade (female) or brown (male); and these mix together in the swirling tide, with each having a light sensitive spot that directs it towards the moon as it sinks in the west (or a flashlight). At dawn the pods dissolve, allowing eggs and sperm to get together and form the new generation. The rising is only on the turn of that one tide and only takes place for a few hours. Actual timing varies each year, and is usually in October, but may be followed by a minor event a month later.

A bowl of Palolo may be seen at http://www.ird.

fr/recherche/santo2006/blog/index_bestanden/13oct/13oct_3_gen.htm

This is worm sex-Pacific style. The pods can accumulate in the sea in massive amounts. Ask the locals about this and if you time it right you may be about to collect some of this rare delicacy, or photo it. They might look yucky, but taste really nice on toast, something like caviar, so I’m told.

 

El Nino and the SOI

AN El Nino occurs when the Earth’s ocean/atmosphere system stores incoming energy from the sun as heat in the sea. Its atmospheric aspect can be measured by a parameter related to the barometric pressure difference between Tahiti and Darwin, a parameter called the Southern oscillation index SOI. This went into El Nino territory briefly in June and more definitely in August and has been very strongly negative throughout September.

This index usually encourages the fronts and disturbed W/SW winds of the southern ocean to visit the NZ/Tasman Sea area. Yet in the past week we have had the opposite weather pattern with a cut-off low feeding easterly winds onto northern NZ—Heavy rain in places which desperately need it.

Weather is truly a mix of pattern and chaos.

 

TROPICAL TOPICS

There are three tropical cyclones and a tropical low at present In the Atlantic is the remains of TC IDA Near the Mexican coast is TC MARTY Near Hawaii is TC NIALA And approaching Taiwan is TC DUJUAN The weekly rain maps, as seen athttp://trmm.gsfc.nasa.

gov/trmm_rain/Events/big_global_accumlation.gif, over the past two weeks show that maximum rainfall in the South Pacific has shifted so that it now is situated between NW of Fiji and the equatorial dateline.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.  There is a lot of activity between Eq. 180 and the NW of Fiji at present.

This is expected to spread eastwards (westerly winds aloft) and stretch across Tuvalu and Tokelau towards Northern cooks and maybe the Tuamotu Islands. A new branch of the SPCZ is likely to form in the Coral Sea later in the week.

 

STR= Sub-tropical Ridge

High us building eats of NZ on Monday and Tuesday UTC and expected to travel east along 35S from Wednesday to Friday with a squash zone of strong trade winds over the Fiji /Tonga/Samoa area in parts on Thu 1  to at 03 Oct.

New HIGH is expected to travel from interior of Australia to Tasman Sea on Fri 2 Oct then travel slowly east along 30S until 4 Oct and then along 40S from Mon 4 to Tues 06 October. On the northern side of this HIGH there is likely to be a squash zone of stronger trade winds over the Coral Sea from 30 Sep UTC stretching onto New Caledonia by Friday 2 Oct and Fiji by Sun 4 Oct maybe lasting at least until 10 October.

 

Travelling Tahiti to Tonga

It is a better looking pattern than last week:

There is a Low well off to the south of Tahiti at present. Its squalls are well off and of no concern but it has “stolen” the winds around Society winds so that departure in net few days are in light winds.

Southerly winds are forecast to return by Tues UTC/Monday local and Se winds from Wed UTC /Tues local. Squash one of strong SE winds and 3

metre+ swells is expected to be strongest over Tahiti area around Sat 3

Oct/Friday local. Remainder of voyage westwards to Tonga basically has SE winds 20 gust 30 knots this week.

 

NZ

NE (onshore) flow onto Northland on Monday to Wednesday as HIGH to east of country builds and finally moves off to the east, Cold front on Thursday is likely to be followed by strong SW flow on Friday 2/Saturday 3 Oct as the front may turn into a Low off the E of North Island.

An intense Low 980 hPa is likely to travel east across South Tasman and South Island along 48S on Sun 4 / Mon 5 Oct, followed by a strong S/SE flow spreading over NZ on Mon 5 Oct and Fiji /Tonga on Wed 7/Thu 8 Oct.

 

Between Tropics and NZ:

There are no comfortable voyages from Tonga or Fiji this week, unless they can reach Northland by Thursday 1 Oct, before the SW winds of 2 Oct.

Departures from New Caledonia or Australia to NZ may be able to cope with these SW winds, and may find the swell bumpy but OK.

>>>>>> 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts– Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom right to subscribe.

To unsubscribe send a reply email saying LEAVE.

 

 

20 September 2015

Bob Blof 20Sep 2015

WEATHERGRAM

YOTREPS

Issued 20 September 2015

Bob McDavitt's ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

Welcome (on Wednesday) to the vernal equinox (in Southern Hemisphere).

Our Sun, viewed from earth, crosses our equator at 08:21 UTC (8:21pm NZST).

The next full moon (fullest at 2:51UTC on Monday 28th Sep) occurs within a few hours of this month’s lunar perigee (closest at 1:46UTC). This just happens to be the closest that the moon gets to earth for the year at 357,

126 km. Yes, this means the full moon this moon will appear to be bigger than normal. It is a perigean moon, some call it a “super moon”. The moon is also going to cross the ecliptic and thus move into earth’s shadow (lunar eclipse). Mid–eclipse is 2:47UTC. This eclipse is best viewed from the America’s, and they are preparing for a “blood moon”, not visible from South Pacific. The reason I’m relating all this background info is that the corresponding tides are called “king tides” or “perigean tides”

and will have higher and lower extremes than normal, reaching their peak around Wednesday 30 Sep. Take adequate precautions.

 

Astronomical data on the 28Sepeclipse is available at http://eclipse.gsfc.nasa.gov/LEdecade/LEdecade2011.html

 

NIWA in NZ have now published their September edition of the seasonal Outlook for the South Pacific at http://www.niwa.co.nz/island-climate-

update-180-september-2015/tropical-rainfall-and-sst-outlook-september-to-

november-2015

 

El Nino is expected to intensify and that is likely to weaken the trade winds and pull the South Pacific Convergence zone north and east of its normal position. There are likely to be bursts of equatorial westerly winds around PNG and Solomon Islands.

Drier than normal conditions are likely around New Zealand and in the New Caledonia/Fiji/Tonga area Note that this is a seasonal forecast, and, as we shall see later in this blog , this week bucks this trend.

Also, cooler than normal sea surface temperatures around New Zealand and in the New Caledonia/Fiji/Tonga area may reduce the likelihood of severe tropical cyclones in these areas.

 

AN El Nino occurs when the Earth’s ocean/atmosphere system stores incoming energy from the sun as heat in the sea. Temperatures in the target zone (measured by the NINO3.4 index) in the eastern equatorial Pacific have now intensified to 2 full degrees above normal as seen at http://www.farmonlineweather.com.au/climate/indicator_enso.jsp?

c=nino34&p=monthly .

They are still intensifying and are expected to peak around the turn of the year.

The graph shows that they still have a while to go to rival the 1997/98 El Nino.

 

TROPICAL TOPICS

There are more tropical features around than last week including two tropical cyclones.

As seen at http://tropic.ssec.wisc.edu/

In the Atlantic we have TC IDA

And off to NE of Japan we have TC KROVANH The weekly rain maps over the past two weeks show that rainfall in the South Pacific is intensifying and extending to the southeast.

Weekly rain signatures for past two weeks, as seen at http://trmm.gsfc.

nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

There is a lot of activity between Eq. and 5S from 160E to 180 at present and this moisture is expected to feed west then S then SE along SPCZ that extends from eastern Solomon Islands to Fiji. Another branch of the SPCZ is expected to linger around tokelay and Northern Cooks.

The 10 day rain accumulations at windyty.com confirms these ideas

 

STR= Sub-tropical Ridge

This is very weak over the Pacific at present.

The High over Australian Bight on Wednesday is expected to spread eat to South Island for Fri/ Sat 25/26 Sep. The reason it is being diverted so far south is because of the cut-off lows in the Tasman Sea. We meteorologists have a name for this pattern – “low index” meaning that one of the zonal parameters we use to measure the weather (Z1) is taking negative values --- the isobars are higher in reading over the South Island rather than the North Island. These low index patterns occur occasionally, even at this time of the year (the equinox) BUT they are the antithesis of El Nino, so I suspect that next High will take a different route and go NE across the Tasman Sea and return us to a “high index” pattern early in October. Meanwhile the eastern and Northern North Island will welcome the rain this week, for the season forecast is for dry, dry, dry.

 

Travelling Tahiti to Tonga

The rain accumulation map shows that it should be dry from Tahiti to Southern Cooks. However, Trough over Tonga on Monday UTC and Niue on Tuesday UTC. After that the trough is expected to weaken and there may be a ridge of light winds along the route—OK for motoring, but not so good for sailing.

The outlook shows a better looking pattern next week.

 

NZ

The cut-off Low located east of Auckland at present should dominate

conditions over the North Island until Wednesday local (some call this

the “olde man southerly” pattern). Then a brief ridge for the North

Island on Thursday.

Another Low is expected to form and cut-off just east of New South Wales

on Tuesday. Its deepening should bring a gale to Sydney/Coffs by

Wednesday. Then this low should travel east along 30S affecting northern

NZ from Friday to Sunday 27 Sep.

 

Between Tropics and NZ:

There are a lot of southerly winds on the western side of these Cut-off

lows until Friday. Things may be OK for a departure after Saturday 26Sep,

not before.

>>>>>> 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage

forecasts– Feedback to bob@metbob.com. Tell anyone you like that to

subscribe they should email me.

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at

bottom right to subscribe.

To send a reply email saying LEAVE.

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