Translator

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

26 April 2015

Bob Blog

WEATHERGRAM
YOTREPS
Issued 26 April 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

Three Chilean Volcanoes have recently thrown ash into the atmosphere;
Calbuco, Caliaqui and Cordon Caulie.
The latest forecast for the VA (Volcanic Ash) shows it drifting into the
South Atlantic: for Volcanic ash advisory see
http://www.smn.gov.ar/vaac/buenosaires/productos.php

The Atmosphere:
The Southern Oscillation Index SOI sums up the weather pattern over the
South Pacific as one number and is based on the standardized difference in
the barometer readings between Tahiti and Darwin (30 day running mean).
It relaxed to zero in early March and then went negative, to be -10 units
for a few weeks in late March/early April, but is now relaxing again. See
http://www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekl
y
If this index remains lower than -10 for four weeks in a row then we have a
fully- blown El Nino, but since it is now relaxing the trend is away from
an El Nino at present.

TROPICAL TOPICS
The tropics are quiet at present. The outlook is for a tropical LOW to form
over Marshall Islands from 4 May.
The rain map for the last two weeks show an increase in activity along the
ITCZ in the Northern Pacific and generally around the South Pacific, and a
decrease in activity in that convergence zone west of Galapagos which has
been a mirror image of the ITCZ and appeared soon after the equinox.
Also notice the intense rain around Sydney. Yuck.
Weekly rain signatures is seen at
http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES

Galapagos to Marquesas:
Good winds for departing on local Monday then fading winds around the
Galapagos.
First of all head for 5S at around 97 to 100W, even though this involves
motoring into light SSE winds. Then the middle leg is westwards along 5 to
6S as far as 125W enjoying a west-ward going current. And then the third
leg is to go direct in SE winds.

SPCZ=South Pacific Convergence zone.
SPCZ is expected to be reasonably intense this week across Solomons/ Tuvalu
and Samoa and may visit French Polynesia for a few days. The part of the
SPCZ over Tuvalu is expected to drift southwards towards Vanuatu/Fiji by the
end of the week, 2/3 May.


STR= Sub-tropical Ridge
STR is reasonable north of NZ this week, Next significant HIGH is expected
to ridge across Tasmania on Wed 29 April and then across the central Tasman
Sea on Thu/Fri and across NZ on Sat/Sun/Mon 2/3/4 May.

Departing from Australian East coast for the tropics this week:
Not a good week for going to the tropics, as that HIGH moving east along the
STR from Wednesday is likely to have a squash zone of enhanced easterly wind
son its northern side. Also a LOW is expected to form off Brisbane on
Thursday/Friday and then move south along the western flank of the then
departing HIGH, the LOW may bring another gale to the Sydney area on Sat and
then weaken and go south.

Departing from Northern NZ for the tropics:
Northern NZ is experiencing a passing active FRONT tonight and on Monday,
then West to SW winds fresh to strong at times on Tuesday and Wednesday,
weakening away on Thursday, followed by light winds in that passing HIGH on
Sat/Sun/Mon 2/3/4 May. As that HIGH travels east, it bunches the isobars on
its northern side into a squash zone of strong SE winds (25 gust 35 knots
and 3 metre+ swells) over, and on the way to, Fiji/Tonga from 1 to 6 May.
Minerva Reef is likely to have strong trade winds from 3 to late on 5 May so
please time your trip to avoid these if you can--- maybe delay departure
from NZ until Thursday, or, if you do depart on Tuesday/Wednesday then go
slow so as to avoid getting north of 25S until after 5 May.

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.

19 April 2015

BobBlog

WEATHERGRAM
YOTREPS
Issued 19-20 April 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 is based on the standardized difference
in the barometer readings between Tahiti and Darwin (30 day running mean)
and sums up the weather pattern over the South Pacific as one number. It
relaxed to zero in early March and then went negative, to be -10 units for a
few weeks in late March/early April, but is now relaxing again.
SOI are shown at
http://www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekl
y

The Ocean
The amount of heat that is being stored in the sea in the Eastern Equatorial
pacific has been above normal since late 2014, as measured by the
NINO3.4index, and is currently increasing.
NINO3.4 as shown at
http://www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi,
confirming a trend towards El Nino.

El Nino s impact: During an El Nino episode, weather patterns tend to be
drawn closer to the equator. The subtropical ridge in the southern
hemisphere tends to be north of its normal position and this weakens the
trade winds. The South Pacific Convergence zone tends to be tugged north and
east of its normal position.

TROPICAL TOPICS
The tropics are quiet at present.
The rain map for the last two weeks show the paths of two cyclone sin the
Indian Ocean, and a weakening of activity in the past two weeks in the South
Pacific. Notice how mirror tropical Convergence zone near 4 to 5S from
near 100W to 130W has weakened in the past week. Weekly rain signatures for
past two weeks, are seen at
http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES

Panama to Galapagos
There are some OK NE wind for departure on local Monday this week and on
local fri/sat/sun 24/25/26 next weekend but otherwise the outlook is no
good: either light wind or contrary wind.
There is a good west going current forecast near 1N and to the Galapagos.

Galapagos to Marquesas:
Good winds for departing mainly local Tues/wed/Thu, but a departure on local
Monday will work ok.
This week a convergence zone is still likely near 4 S from 100W to 130W,
avoid this by heading for 5S between 95and 100W. There is a good west going
current along 5S from 100W to 120W.
By local Tuesday 28 April; Winds around Galapagos, as seen at www.
windyty.com, showing bands of counter-wind: west and SW winds near the
equator kicking in:
This is an El Nino sign. Note how the trade winds are staying undecided
to south of 5S.

SPCZ=South Pacific Convergence zone.
SPCZ is reasonable north of NZ this week, A High cell is expected to form
East of the South Island by Tuesday 21 April and then travel east along
45S, so that it bananas a low on its northern side, east of NZ; no good
for cruising.

STR= Sub-tropical Ridge
SPCZ is reasonable north of NZ this week, Next significant HIGH is expected
to ridge into central Tasman Sea AROUND
2-4 May, not before.

Departing from Northern NZ for the tropics.
Good to go on Monday and OK to go on Tuesday but a departure on Wednesday is
likely to encounter fresh head winds for a while from a passing trough on
Sun 26 April.

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.

12 April 2015

Bob Blog

WEATHERGRAM
YOTREPS
Issued 12 April 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 sums up the weather pattern over the
South Pacific as one number and is based on the standardized difference in
the barometer readings between Tahiti and Darwin (30 day running mean).
It switched briefly blue and positive at the start of March but has now
gone very negative again. If it stays this negative for 2 more weeks then we
can call this an El Nino event.
SOI is shown at
http://www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekl
y

The Ocean
The amount of heat that is being stored in the sea in the Eastern Equatorial
pacific has been above normal since late 2014, as measured by the NINO3.4
index.
NINO3.4 is shown at
http://www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi,
confirming a trend towards El Nino.

During an El Nino episode, weather patterns tend to be drawn closer to the
equator. The subtropical ridge in the southern hemisphere tends to be north
of its normal position and this weakens the trade winds. The South Pacific
Convergence zone tends to be tugged north and east of its normal position.

TROPICAL TOPICS
In last week s weathergram we looked at the possibility of a tropical
cyclone forming in the Coral Sea by 20 April: well, this happened earlier
than expected and TC SOLO moved quickly across the Loyalty island
group today. There may still be one more cyclone forming around 20 April,
to finish off the season, and now it is more likely to form around the Timor
Sea, rather than the Coral Sea.
Observations from http://www.wunderground.com for Noumea Airport as TC
SOLO went past show that basically it was a gang of squalls.

In the Indian Ocean, east of La Reunion Island, Tropical cyclone JOALANE is
traveling south and intensifying.

The rain map for the last two weeks show the paths of two cyclone sin the
Indian Ocean, an d the build-up of activity in the past week in the Coral
Sea. In the past week the ITCZ has restored to normal intensity and
position, and there is a mirror tropical Convergence zone near 4 to 5S
from near 100W to 130W. Weekly rain signatures may be seen at
http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES
Panama to Galapagos
Maybe too late now to get a good voyage along this route. The head
component of a S/SW wind is spreading north across the zone. There is a
good south going current especially near 82W from 5N to 2N.

Galapagos to Marquesas:
This week a convergence zone is likely between 4 and 5S from 100W to 130W,
avoid this by heading for 6S between 95and 100W. Trade winds are south of 5S
and may be unlikely to get any further north because of that convergence
zone have been moderate to strong for the past week, but if the El Nino
continues to kick in then winds may ease a lot in the next week or so. There
is a good west going current along 5S from 105W to 120W.

Winds around Galapagos, from www.windyty.com, show bands of counter-wind:
west and SW winds near the equator kicking in by Thursday: an El Nino sign.
The trade winds are staying south of 5S.

SPCZ=South Pacific Convergence zone.
SPCZ is reasonable active and spread out into different branches. Lows are
likely to form over or around Pitcairn Islands on Wednesday and Friday.

STR= Sub-tropical Ridge
The STR extends from Australian Bight across Australia to Tasman Sea then to
north of NZ and then cycles north and south across the South Pacific. Next
HIGH to cross Tasman Sea on Tues/Wed 14/15 should fade over northern NZ by
Fri 17 April.

Departing from Northern NZ for the tropics.
It will certainly feel cold enough for departure by mid-week, as a Low
deepens east of NZ, directing air from the Antarctic ice shelf to NZ.
And when these SW winds start easing on Wednesday there is a good
opportunity for any early-birds who would like to get off to the north or to
Australia On Friday and Saturday another cold front is expected to usher in
another southern change across the Islands.

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.

05 April 2015

Bob Blog

WEATHERGRAM
YOTREPS
Issued 5 April 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 is based on the standardized difference
in the barometer readings between Tahiti and Darwin (30 day running mean)
and sums up the weather pattern over the South Pacific as one number. It. 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. If it stays this
negative for 3 more weeks then we can call this an El Nino event then again
it may just relax again as it did last November.
SOI is shown at
http://www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekl
y

TROPICAL TOPICS
We are now in a period of suppressed convection over the South Pacific and
this should last throughout the coming week. The next period of enhanced
convection is forecast to reach northern Australia around mid- April and
then move into the Coral Sea around 20 April.
There is a build-up of convection in the south Indian Ocean and some
tropical lows are forming in that basin.
In the Northwest Pacific TC MAYSAK is travelling westwards across the
northern Philippines, and expected to weaken in the China Sea. Another
cyclone has formed near Chuuk, TC HAISHEN , and it is expected to weaken and
go north.

The rain map for the last two weeks show a buildup in the activity in the
South Indian Ocean and a weakening in the activity in the South pacific.
Weekly rain signatures for past two weeks, may be seen at
http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES
Panama to Galapagos
There is a NE flow around Panama until about local Tuesday and then this
fades. Later in the week the head component of a S/SW wind is expected to
form along the route to Galapagos. So go by local Tuesday if you can.
Good west going current from 2N 85W to Galapagos.

Galapagos to Marquesas:
This week a convergence zone is likely to form along about 5S from 100W to
140W, avoid this by heading for 6S between 95and 100W. Trade winds south of
5S have been moderate to strong for the past week, but if the El Nino
continues to kick in then winds may ease a lot in the next week or so. There
is a good west going current along 5S from 111 to 125W and along 6S from
103W to110W.

SPCZ=South Pacific Convergence zone.
SPCZ is scattered and weak. However a Low is likely to form around Southern
Cooks/Australs from Wednesday, and increasing convection is likely over the
Coral Sea from around 12 April 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 extends from Australian Bight to north of NZ and then along 40 to
35S across the pacific.
Next HIGH to cross Tasmania into the Tasman Sea is expected to do so on Fri
10 April, and may take until Fri 17 April before it reaches NZ.

Over NZ
A period of lows. First one is already deepening in Tasman Sea and should
deepen a lot as it passes by southern NZ on Monday. Second is expected to
deepen off Sydney on Tuesday and weaken over central NZ on Thursday/Friday.

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