Translator

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

29 March 2015

Bob Blog

WEATHERGRAM
YOTREPS
Issued 29 March 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 Atmosphere:
The Southern Oscillation Index SOI (30 day running mean) sums up the weather
pattern over the South Pacific as one number. It is based on the
standardized difference in the barometer readings between Tahiti and Darwin.
It switched briefly blue and positive at the start of March but has now gone
very negative again, as Tahiti drops below normal atmospheric pressure and
Darwin returns to normal pressure after recent weather.

TROPICAL TOPICS
The recent cluster of tropical cyclones may be related to a recent Madden
Julian Oscillation MJO that travelled eastwards across the South Pacific.
This can be seen as the blue/purple spread in the Outgoing Longwave
radiation anomalies observed by satellite ad graphed in this longitude-
timeline. Basically in periods of very active weather there is more cloud,
and the more white cloud there is, the lower the amount of radiation that
can escape to space / the lower (bluer) the OLR.
OLR can be seen at
http://cawcr.gov.au/staff/mwheeler/maproom/OLR_modes/h.6.MJO.S.html

This shows a yellowish-orange zone is forecast to travel east across the
South Pacific over the next week or two. This is a zone of positive OLR,
meaning less cloud than normal, and that suggests a weaker South Pacific
convergence zone.
This also shows that another MJO event is being forecast for mid to late
April that will be the last chance for cyclones in the South Pacific this
Cyclone season.

In the Northwest Pacific TC MAYSAK has formed over Palau and is expected to
travel west towards Philippines it may peel off to the north or it might
possibly make landfall around 5/6 April. Too early to tell, so be watchful.

The Cyclone that I mentioned the models were predicting to form over
Northern Cooks last Friday/Saturday never actually developed at all. AT
present it is between Niue and Southern Cooks and it does has some squally
showers, but nothing worth writing a book about.

The rain map for the last two weeks show a shift eastwards and weakening of
the strongest convective activity in the South Pacific, and a build-up of
convection in the NW pacific. Weekly rain signatures can be seen at
http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES
Panama to Galapagos
May be a good idea to wait for the onset of the next period of NE winds on
local Tuesday. If you do this then you can take a direct trip, and no need
to take the Isla Mapelo diversion. Good west going current from 2N 85W to
Galapagos.

Galapagos to Marquesas:
Light winds at the start--- head for 5S to 6S ASAP to get into the trade
winds. Best day to depart this week could be local Monday/Wednesday
(northerly winds for starters).

SPCZ=South Pacific Convergence zone.
SPCZ is weakening away and mainly over Samoa to Southern cooks at the
beginning of the week. Another new branch may form over central Coral Sea
to Vanuatu by end of week.

STR= Sub-tropical Ridge
The STR was knocked to north of NZ during the past week, and the
northwards-knock is expected to be taken east this week as the remains of TC
REUBEN travel ESE into the mid latitudes. The low that has been over NZ
this weekend is expected to go east and fade by Wednesday UTC.
HIGH that follows that Low should travel across central Tasman Sea on
Monday/Tuesday and central/northern NZ on Wednesday/Thursday.
Next HIGH is shaped like an Easter Egg and should travel east across
Tasmania on Thursday and then across southern Tasman Sea on Friday and then
travel NE across NZ on Sat/Sun/Monday.

Over NZ
The incoming HIGH on Thursday is shovelling cold air from the southern Ocean
onto NZ ahead of it. Thus a cold front, preceded by strong NW winds and
followed by chilling southerlies, is expected to travel NE across the South
Island on Thursday and the North Island on Friday. Then clearing condition
by Saturday. In Northern NZ expect an increasing NW flow for the annual
Auckland-Tauranga yacht Race starting on Thursday, and strong and squally SW
change during Friday, and a change to easing SE winds by Saturday.
======
The first full moon after the equinox occurs on Sat 4 April this is the
Jewish Passover: the Sunday after it is the Christian Easter Sunday. In
AD33 the Passover Full moon was on a local Friday, this year it is on a
Saturday and there is a lunar eclipse as well visible from the Pacific (full
eclipse at 1am Sunday for Auckland). Rather strange to see the Easter moon
come and go so quickly.

The late Augie Auer would study the position and intensity and trend of all
the weather zones around the planet at the March equinox very carefully, for
he thought of this as the start of the meteorological year and that any
trends happening now will not wobble or fade, but will continue and mark the
year ahead.

Indian Ocean
You may have heard of the loss of a Catamaran (3 People on board) in the
Indian Ocean last month. A possible life-raft has now been observed at
24.317346S, 72.127445E. If you can help by spending time scanning incoming
real time hi-resolution satellite data then the Facebook page is
https://www.facebook.com/groups/1550511385236726/1569388596682338/?notif_t=g
roup_activity
Many thanks

See my yotpak at boatbooks.co.nz/weather.html for terms used.
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.
My website is at metbob.com Feedback to bob@metbob.com To unsubscribe send
a reply email saying LEAVE.

22 March 2015

Bob Blog

WEATHERGRAM
YOTREPS
Issued 22 March 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 Atmosphere: PAM and BAVI (and maybe NATHAN as well) were
triggered by a period of strong equatorial westerly winds (strong enough to
affect Kiribati and Tuvalu early in March).
This reversal of the trade winds is likely to result in the warmer than
normal sea surface that has recently been in the western equatorial Pacific
to shift east during the next few months, and this may show as a tendency to
El Nino. The atmosphere seems to be going hat way already, as seen by the
behaviour of the SOI diving negative in past two weeks, but that may just be
because of lower-than-normal pressures recently over French Polynesia.
The Southern Oscillation Index SOI (30 day running mean) sums up the weather
pattern over the South Pacific as one number. It is based on the
standardized difference in the barometer readings between Tahiti and Darwin.
It switched briefly blue and positive at the start of March but has now gone
negative again.

TROPICAL TOPICS
NATHAN has weakened a lot since last week and travelled west. It is still
travelling west, towards Darwin, and should fade away by
Wednesday.
We jumped the letter Q after PAM and the next cyclone is a tropical low that
has formed over the Lau group of Fiji. Named REUBEN it is category 1 and
expected to wobble SE then S and weaken over the over sea: Latest on REUBEN
can be seen at http://www.met.gov.fj/aifs_prods/65648.html
Another cyclone is expected to form over the Northern Cooks by Tuesday UTC
and deepen to a very intensive system by Fri/Sat 27/28UTC near Niue
(Thursday/Friday local). Brace for possible major damage.

The rain map for the last two weeks show a shift eastwards of the strongest
convective activity in the South Pacific has shifted eastwards to the
Northern Cooks.

WEATHER ZONES
Panama to Galapagos
OK N/NE winds for starting this week from Panama. Head for west end of Isla
Mapelo and then go direct. The ITCZ is occasionally bringing tropical
downpours on this route between 5 and 4N. There is a strong west-going
current forecast near 1N from 84 to 87W.

SPCZ=South Pacific Convergence zone.
REUBEN is already out of the SPCZ and taking a piece of its energy out of
the tropics.
SPCZ is very intense this week over Samoa to Northern Cooks and this is
expected to help a cyclone form over Northern cooks by Tuesday UTC (Monday
local).

STR= Sub-tropical Ridge
The main STR is returning to its normal latitude at 40S around NZ.
A HIGH is expected to build east of NZ on Monday and Tuesday and then move
off to the east on Wednesday and Thursday allowing the remains of REUBEN to
travel south along 170W behind it.
The next high is then expected to travel in a thin line across the south
Tasman Sea on Saturday (while a Low lingers in the Tasman Sea) and then
blossom east of the South Island on Sunday and move off to the east on
Monday 30 March.

Over NZ
The low currently spinning in the Tasman has no traction and is likely to
fade away there by Wednesday, but may bring bothersome showers to the
cricket (semi-final) at Eden Park on Tuesday.
Another low is expected to cross the Tasman Sea on Tuesday and Wednesday and
fade over North Island on Thursday/Friday.
Another low is expected to cross the central Tasman Sea on
Thursday/Friday/Saturday/Sunday and then NZ on Monday and Tuesday
30/31 March.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
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.
My website is at metbob.com Feedback to bob@metbob.com
To unsubscribe send a reply email saying LEAVE.

15 March 2015

Bob Blog

WEATHERGRAM
YOTREPS
Issued 15 March 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 TOPICS There were six named storms on the planet
last Thursday and three of them are still going:
Cyclone PAM peaked at Category 5 on 12 March, and brought damaging
conditions to Vila on Friday 13/Saturday 14th. Early on the 13th it
reached its peak with estimated gusts near centre of 270kph. It started to
weaken on the 14th -at one stage on the 14th Fiji MetService estimated its
central pressure to ne 896 hPa. The lowest ever (estimated) central
pressure in a tropical cyclone remains 870 hPa in Typhoon TIP in October
1979.
It has been hard to get real data from Vanuatu during PAM, and the Island
weather stations stopped sending data (maybe damaged, maybe lost power) as
it approached, but did measure a strange pressure blip near the eyewall.
They measured winds up to 100kph before failing and pressure down to 972
hPa.
PAM has left the tropics and is moving towards but to south of Raoul island
:

Raoul Island Data has observations now with wind around 75kph and pressure
around 995hPa, still falling

PAM's wind are affecting east coast of northern NZ, with winds at Channel
Island, Colville Channel, east of Auckland at 50 gust 70 knots.

PAM is now encountering increasing NW winds aloft as seen in the jet stream
maps, --these will steer it all to the southeast, and once the remains of
PAM get under the jet (Sunday night), the upper winds will knock the top off
the system, and the lower part might curve to the south again a little.
Track of PAM may be seen at
http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/warnings/sh1715.gif
If PAM took its tropical exit a day or so later in may have encountered a
cold front and the cold southerly winds that follow this front--- this
ingestion of cold air can sometimes cause the cyclone to redevelop.

NZ MetService have arranged it so that their duty-lead meteorologists have
been able to write down their thoughts about PAM on a real-time basis ---
The entire blog is available at
http://blog.metservice.com/2015/03/tropical-update-mar15/

BAVI is PAM s equatorial twin, and is now travelling almost due west towards
Philippines and is expected to weaken

NATHAN bounced back to the east into the Coral Sea and is expected to
shift to the south is a few days. After that its future is uncertain at this
stage. Its track can be seen at
http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/warnings/sh1815.gif
The rain map for the last week shows that the 6 wettest areas have been
associated with tropical cyclones even the one in the South Atlantic.

WEATHER ZONES
Panama to Galapagos
After the equinox (21 March) it is normal for the periods of NE winds on
this route to become weaker, fewer and further apart. There are some
weak to moderate NE winds for the start of this trip until Saint Patrick s
Day Tues 17 March local , and then just light winds until around 25 March.
The ITCZ is occasionally bringing tropical downpours on this route between 5
and 4N. To use the available current optimally head to SE of Isla Mapelo
and then gradually turn to Galapagos.

SPCZ=South Pacific Convergence zone.
SPCZ is expected to intensify during the coming week across Tuvalu to
Fiji/Tonga and also Samoa to French Polynesia. A tropical depression may
form on the SPCZ next Friday 20 March near Samoa and may travel toward Niue.


STR= Sub-tropical Ridge
The main STR is now NORTH of NZ but returns to 35 to 40S in the eastern
Pacific.
A rather slack High pressure area is expected to cross the Tasman on Tuesday
and Wednesday and then NZ on Thursday and Friday.

Over NZ
The remains of PAM are expected to side swipe eastern areas on Monday and
Tuesday and still be big out to east of South Island on Wednesday. A
challenge for the (delayed) restart of the Volvo Round-the-world Yacht race.

After the light winds of a passing high on Thursday and Friday, the outlook
is for more wind and rain as a trough crosses NZ on Saturday/Sunday and a SW
flow on Mon /Tues 23/24 March.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
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.
My website is at metbob.com Feedback to bob@metbob.com To unsubscribe send
a reply email saying LEAVE.

08 March 2015

BobBlog

WEATHERGRAM
YOTREPS
Issued 8 March 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

First of all are any of you sailing from Australia to the islands of Papua
New Guinea or Solomons this year, especially around August/ September? If
so please read the article starting at page 36 on
http://thecoastalpassage.com.au/papers/tcp71.pdf This tells the story
of Hans Clemmensen on SV Seagoon in Cairns who is seeking yachts to help him
get solar panels to islanders in these areas. If you would like to help
then contact him on svseagoon@yahoo.com, or read more on his websites
http://yachtseagoon.bravehost.com and blog on
http://yachtseagoon.blogspot.com.au

The Atmosphere: The Southern Oscillation Index SOI (30 day running mean)
sums up the weather pattern over the South Pacific as one number. It is
based on the standardized difference in the barometer readings between
Tahiti and Darwin. It has been negative since last July but has risen to
take positive values in the past two weeks. Maybe this autumn will be like
last autumn?

TROPICAL TOPICS
There are two small tropical lows at present in the Indian Ocean and a weak
one near Marshall Islands, but the main tropical low worth watching is the
one that is presently named 93P or 11F, near 8S 170E , between Tuvalu and
Santa Cruz Islands.
This depression is still in the formative stage of becoming a Tropical
Cyclone and is expected to do so on Monday, and then affect Vanuatu on
Wednesday and Thursday and then go off to the SE.
This is likely to become a twin or triplet--cyclone event--- another cyclone
may form in the Coral Sea near the Australian coast by Wednesday and also
travel to SE, close to south side of New Caledonia by Monday 16th March.
And a third may briefly form off the NW Australian coast on Wednesday and
travel SW/S and fade by Saturday.
The rain map for the last week shows that the wettest area at present is in
the Kiribati/Tuvalu area, with other rain maxima near Port Hedland (NW
Australia) and on west and east side of Madagascar.
During February the averaged isobars show a zone of high pressure zone
straddling from south Indian Ocean across NZ to west of the Andes: this is
the Subtropical ridge.
Looking at the anomaly map, As seen at http://www.esrl.noaa.
gov/psd/map/images/fnl/slp_30a.fnl.anim.html, shows that during February
there was often a blocking High between the Australia Bight and NZ. This
explains the recent light winds and dry weather. This pattern is now
changing, as shown this weekend, when a front from the southern ocean was
able to cross all of NZ (albeit briefly).

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is expected to intensify during the coming week between Coral Sea and
Samoa and may trigger the formation of two tropical cyclones.

STR= Sub-tropical Ridge
A rather slack High pressure area I expected to cross NZ from Monday to
Wednesday.
The next HIGH is expected to travel from Australian bight across Tasmania on
Friday and then stall in the Tasman Sea over the weekend, nicely placed to
help divert the tropical cyclone that may then be north of NZ off to the SE.


Over NZ
Mixed weather from Monday to Wednesday with reasonably light winds but a
scattering of showers in a weak ridge.
A front is expected to cross NZ on Thursday and Friday followed by a
southerly on Saturday, and then a SE flow over northern NZ on Sunday in time
for the Volvo restart, with strong southerly winds/big southerly swells
still lingering off the NZ east coast.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
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. My website is at metbob.com Feedback to
bob@metbob.com To unsubscribe, send a reply email saying LEAVE.

01 March 2015

Bob Blog

WEATHERGRAM
YOTREPS
Issued 1 March 2015-a special day for any Welsh called David.

Bob McDavitt's ideas for sailing around the South Pacific.
The Ocean: During 2014 extra heat was stored in the Pacific Ocean, and
Oceanic indices were in El Nino territory for a while. This year there are
still above average SST in the western Pacific, but SST has reverted to
normal in the eastern and central Pacific.

The Atmosphere: The Southern Oscillation Index SOI (30 day running mean)
sums up the weather pattern over the South Pacific as one number. It is
based on the standardized difference in the barometer readings between
Tahiti and Darwin. It has been negative since July and dived below -10
(Australian units) for much of September, and again for a week in November,
and in late January, and in the last week has relaxed to near zero.

TROPICAL TOPICS
Apparently TC MARCIA might have only spent a brief time of its life at
Category 5. The important lesson is that these small sized cyclone can pack
a (briefly) big punch, especially in March, and so we should treat them with
the utmost respect.
At present TC GLENDA is over the open sea in the Indian Ocean.
No tropical cyclones are expected in the South Pacific this week, but people
in the Solomons are at risk during next week 10-13 March.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ should slowly intensify this week in the Coral Sea.
A tropical trough mid-week over Fiji/Tonga/Niue/Southern Cooks is not
expected to come to much, but IS expected to help form a Low by the local
Wednesday south of Southern Cooks and this should then move off to the SE,
killing the winds over Southern Cooks.

NIWA have produced a map showing the expected position of the SPCZ in March
and April (green line, with white whiskers at 1 and 2 standard deviations).
(They do not tell us what the red line indicates).
see
http://www.niwa.co.nz/island-climate-update-173-february-2015/south-pacific-
convergence-zone-forecast-february-to-april-2015


STR (Sub-tropical Ridge) and over NZ
The STR is still over northern NZ, as is typical of this time of the year.

South of the STR are the roaring 40s, and the fronts in this zone are having
impact over the South Island and having increasing impact over the North
Island. One of these fronts should cross South Island and central NZ on
Monday and Tuesday. After a brief respite on Wednesday a stronger front is
expected over the South Island on Thursday and the North Island on Friday,
followed by SW/W flow over most of NZ (not the far north) on weekend of 7/8
March. The seasons are changing.

NZ farmers may talk of dry soils in parts of NZ, but the NIWA SPI graph
shows mostly average rainfall during February.
See http://www.niwa.co.nz/static/climate/last30daysspi.png?1234

See my yotpak at boatbooks.co.nz/weather.html for terms used.
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. My website is at metbob.com Feedback to bob@metbob.com

To unsubscribe send a reply email saying LEAVE.

Blog Archive