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

29 January 2017

Bob blog 29 JAN 2017

WEATHERGRAM
YOTREPS
Compiled Sun 29 January 2017

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 Tropics in the South Pacific/Australia region are starting to show signs of
life, with a Tropical depression today off the NW of Australia travelling West
and then likely to go WSW into Indian Ocean.
There is a pulse of extra convection now in the Indian Ocean and travelling
eastwards towards Australia. This is a Madden Julian Oscillations. It is
expected to weaken as it moves across Australia next few weeks but may intensify
when it reaches South Pacific by mid-February. This area of enhanced convection
shows as a bubbly blue area in the OLR (Outgoing Longwave Radiation)
extrapolations that may be seen at
www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjoupdate.ppt

We can see the enhanced rain in the Indian Ocean that is associated with this
MJO in the past two weekly rain maps at
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif. One trend shown
by these two maps is the burst of heavy rain two week ago near Tahiti (by a
passing depression), now relaxing. Also, we can see that the ITCZ is
intensifying near Indonesia and Majuro.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is expected to stretch from Solomons to Southern cooks.
A topical depression is expected to form to south of French Polynesia on weekend
of 4/5 Feb local. Later this month we can expected deeper developments so if you
want to avoid cyclones and Island hop, then this is your week, and no later.

Subtropical ridge (STR)
Highs near 35S over northern NZ for Auckland Anniversary weekend is expected to
move off to the east during the week.
For Waitangi Day-weekend a High is expected to travel east across central NZ on
Sat/Sun followed by a ridge over northern NZ on Monday. Bon chance.

Tasman Sea/NZ Area troughs.
A front is expected to travel NE across South Island on Tuesday and Wednesday,
then stall and fade over southern North Island on Thursday. This is followed by
a southern dip in the Sub tropical ridge/ STR
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See my website www.metbob.com for information on tailor-made voyage forecasts-
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22 January 2017

Bob Blog 22 Jan 2017

WEATHERGRAM
YOTREPS
Compiled Sun 22 January 2017

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 Tropics are still having a quiet period between active cyclones.
Rather unusual for the to be so quiet for so long.NASA has noticed this anomaly
and is Facebooking about it at www.facebook.com/NASAHurricane/

My theory, as far as South Pacific is concerned is that the recent temperature
anomaly between (hotter than normal) Australia and (colder than normal ) NZ has
been producing more westerly winds, knocking the subtropical ridge north of
normal, and thus weakening the SPCZ. We had those two deep low across NZ as
mentioned in last week's weather gram, and I think this means the subtropical
ridge is now about to be able to shift south onto central/southern NZ during
next few weeks.

Rain maps show that an active low affected the area south of Southern cooks and
French Polynesia last week, and changes elsewhere were minimal.
Rain for the past fortnight may be seen at
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ remains about the same this week as last week, expect for noticable
activity in the Fij/Tonga/Niue area culminating in development of a tropcial low
south of Niue at 25S by end of the week. That low is expected to travel slowly
south next week.
Check out the expected tropical accumulated rainfall for next week from
windyty.com

Subtropical ridge (STR)
High in central Tasman sea on Monday is expected to fade over northern NZ by
Wednesday.
A new High is expected to spread into the south Tasman Sea on Thursday, and
cross central/northern NZ area on Sunday 29 Jan.

Tasman Sea/NZ Area troughs.
A deep low is expected to move off to southeast of NZ on Monday (23rd Jan)
A front is expected to cross South Island on Tuesday and North Island on
Wednesday.
Another front is expected to cross South Island on Sunday and North Island on
Monday 30 Jan. This is Auckland Anniversary day, so anticipate a change around
then to SW 20 gust 30 knots.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Follow me on Facebook at www.facebook.com/metbobnz/
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.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

15 January 2017

Bob B15 Jan 2017, When is it best to depart America for Galapagos/Marquesas?

WEATHERGRAM
YOTREPS
Compiled Sun 15 January 2017

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 new edition (the third) of The Pacific Crossing Guide by Kitty Van Hagen is
now available, and this edition gives reference to MetBob as well. So, I
recommend it as a useful source of info if you are planning on voyaging around
the South Pacific this year.
Google it and buy from you favourite supplier/Bookshop. The nearest to me is
www.boatbooks.co.nz/cruzeswpac.html#30125

ANTARCTICA CUP
This week Lisa Blair is setting off for the "Antarctica Cup" racetrack,
departing from Albany in southwest Australia. See
www.acronautic.com/antartica-cup-ocean-race/
I consider her to be a worthy sailor and I shall be sponsoring this adventure by
watching the weather for her. Lisa is doing this to spread the word about
Climate change- her vessel has been renamed CAN for Climate Action Now. This is
indeed a worthy cause and I encourage you to track her proceedings at
lisablairsailstheworld.com/blog or www.facebook.com/LisaBlairSailstheWorld/ and
spread the word.
Her departure was meant to be today but has been delayed a few days by an
electrical fault.

When is it best to depart America for Galapagos/Marquesas?
The South Pacific cyclone season ends in April, and the Northeast Pacific
cyclone season starts in June, so it is generally understood that the best time
to depart San Diego or Western Mexico or Panama for Galapagos or Marquesas is
between mid-February and early June, crossing the equatorial area between
cyclone seasons.
In an El Nino year there is a low risk of strong winds near Marquesas in
April/May - but this is NOT an El Nino year. Departing too early means possibly
being caught in a zone of light winds between equator and 10S, especially east
of 100W, but there are usually some useful currents to follow.
One thing I'd like to point out, is that soon after the March 21st equinox (when
the overhead sun starts shifting northwards into the northern Hemisphere) the
prevailing winds between Panama and the equator swing from "occasionally NE" to
"mostly SW", so that makes departures from Panama in April onwards difficult.
This can be gleaned by checking the monthly averaged ocean winds from
Scatterometer data as gathered for sailors by the crew of at SV PITUFA at
http://www.pitufa.at/oceanwinds/

The Tropics
The Tropics are still having a quiet period between active cyclones. There is a
little activity over the sea off southeast Asia: Tropical depression 01W (ONE)
is heading for southern parts of Vietnam, as seen at metoc.ndbc.noaa.gov/
Rain maps from trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif
show that activity is on the decrease around Indonesia and SE Asia, and on the
increase around central and NE of Australia

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is active this week mainly east of 180, and this reflects the warmer than
normal sea temperatures between Fiji and Tahiti. The depression that is tonight
to south of Niue (and has been around a few days now) is expected to remain
slow-moving and fade by nid week. However, a new LOW is expected to form to
southeast of Rarotonga and south of Papeete on Wednesday, and this feature
should deepen and travel slowly east late this week, bringing squally NW winds
to parts of FP French Polynesia and cooler clearer southerly winds + SW swells
to Southern Cooks.
Tropical accumulated rainfall for next week may be seen at windyty.com
Sea Surface temperature anomalies may be seen at
www.ospo.noaa.gov/data/sst/anomaly/2017/anomp.1.12.2017.gif

Outlook for next cyclone:
Still too far away to be sure, but Meteo France are picking an increasing
likelihood of tropical cyclone formation over Vanuatu between 22 and 28 Jan as
seen at www.meteo.nc/nouvelle-caledonie/cyclone/coin-des-experts
This prognosis takes into account the MJO cycle (rather weak at present) and sea
surface temperature changes.

Subtropical ridge (STR)
High in North Tasman sea on Sunday is expected to fade over northern NZ by
Wednesday.
A new High is expected to spread into the south Tasman Sea on Thursday, and
cross NZ area on Friday.

Tasman Sea/NZ Area troughs.
A deep low is expected to cross southern NZ on Wednesday bringing strong winds
and a brief cold SW change on Thursday.
After that Thursday/Friday High, be on watch for a LOW from central Australia to
deepen quickly over the warmer than normal seas off Sydney on Friday, and then
deepen more as it crosses Tasman Sea on Saturday and central NZ on
Sunday/Monday. Avoid.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Follow me on Facebook at www.facebook.com/metbobnz/
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 others 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.
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08 January 2017

Bobgram issued 8 Jan 2017

WEATHERGRAM
YOTREPS
Compiled Sun 08 January 2017

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.

Are we having a La Nina?

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. A La Nina event
occurs when the SOI is more than plus one (standard deviation from its mean) for
more than a month.
Over the past few weeks the SOI has been positive, but has been in "neutral
territory".
This can be seen at
www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekly

The Ocean: The target area for measuring the sea surface temperature as an index
is the eastern equatorial Pacific, and the index is called NINO3.4. This has
been cooler than normal for the past seven months but it now relaxing.

The monthly numbers for NINO3.4 show how the 2016 EL NINO compares with the 1998
EL NINO
at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=nino34&p=monthly

SO, in summary, we are in neutral territory at present. Even so, the subtropical
ridge in the southern Hemisphere has been hogging 35S recently and is expected
to drift SOUTHWARD over New Zealand for the next month or so, and may visit
central NZ and the South Island mid to late February.

The Tropics are quiet at present. There are a couple of tropical depressions
near Asia and their possible tracks this week may be as seen at
http://ruc.noaa.gov/tracks/

Rain maps show that activity is on the increase around Indonesia and SE Asia,
steady around the Coral Sea, and decreasing elsewhere, as seen at
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is active between the Coral Sea and Tonga. A small depression may move
along this zone and visit New Caledonia on Monday and be at 30S to South of
Tonga by Friday 13 Jan UTC.

Subtropical ridge (STR)
High in North Tasman sea on Sunday is expected to slip along 33S, north of NZ
mid-week, and then further east from Thursday.
A new High is expected to spread into the mid/south Tasman Sea on Thursday and
spread east along 37S across NZ on Friday UTC, followed by a prefrontal NW flow
on Sat 14 Jan

Tasman Sea/NZ Area troughs.
Disturbed westerly flow until Wednesday, then a FRONT is expected to cross NZ on
Thursday, followed by SW change on Friday 13 Jan, then another FRONT on Sunday.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Follow me on Facebook at www.facebook.com/metbobnz/
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 January 2017

Bob Blog 1 Jan 2017

WEATHERGRAM
YOTREPS
Compiled Sun 01 January 2017

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.

Auld Lang Syne says welcome to the New Year, and to fresh beginnings.

In hindsight, during Dec 2016 the Subtropical ridge in the South Pacific
slightly further south than normal and more intense than normal in the Tasman
Sea (and around Madagascar). The Subtropical ridge in the northern hemisphere
has been stronger and further north than normal too. These are traits of the La
Nina weather pattern, and in recent weeks the ENSO/SOI values have been slightly
positive, showing a weak la Nina. West Australia has had lower than normal
pressures, thanks to the Monsoonal Low which started out as Yvette.

Average isobars for the past 30 days and their anomaly may be seen at
www.esrl.noaa.gov/psd/map/images/fnl/slp_30b.fnl.html

Last 30 days of rainfall, and its anomaly, are seen at TRMM
trmm.gsfc.nasa.gov/trmm_rain/Events/thirty_day.html

Tropical cyclone NOCK TEN brought extensive wind and rain damage to Philippines
during Christmas and Boxing Days

The Tropics are quiet at present. Be watchful in the Coral Sea area as that may
be where a tropical depression may appear by end of this week.
Rain maps show that activity is on the increase in the Coral sea area.
see trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is active and consists of several discrete convergence zones spanning the
entire South Pacific.
The accumulated rainfall forecast map from windyty.com shows a wet week ahead
almost everywhere, but New Caledonia may escape.
Active SPCZ extends from east of Solomons/Rotuma to Tonga /Niue tonight and is
expected to drift south or southwest slowly over Fiji and weaken next few days.
Another Convergence is likely to take over in the Coral Se area by the end of
the week.

Subtropical ridge (STR)
The slow-moving ridge located to NE of NZ is expected to linger there this week.
The next HIGH is expected to travel east across Tasmania on Tuesday and then
northeast across the Tasman Sea reaching northern NZ on Friday where it weakens
into a ridge that merges with the one already to NE of North island.
Another High is expected to travel east across the Tasmania area into South
Tasman sea on Friday/Saturday.

Tasman Sea/NZ Area troughs.
Trough travelling across North Island tonight and Monday. Another trough is
expected to follow on Tuesday afternoon/night, and deepen into a low east of NZ
on Wednesday. Avoid the southerly winds and swells of this. Another trough is
likely over the North Island late Friday/Saturday followed by SW winds.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Follow me on Facebook at www.facebook.com/metbobnz/
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.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

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