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

26 October 2014

Bob Blog issued 26 Oct

WEATHERGRAM
YOTREPS
Issued 26 October 2014
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 Coming Cyclone Season

NIWA has issued a Tropical Cyclone outlook for the coming South Pacific
cyclone season.
For the details go to (www.scoop.co.nz/stories/SC1410/S00048/southwest-
pacific-tropical-cyclone-outlook.htm
)
In summary NIWA expect the coming season to bring a near average number of
cyclones (8 to 12 in all), with the normal slow start, and February/March
peak.
VANUATU and NEW CALEDONIA are expected to have lower than normal risk.
A zone of slightly higher than normal risk is expected to stretch from
TUVALU across TOKELAU/SAMOA, to between NIUE and SOUTHERN COOKS. These are
expected to be only small variations from normal and so vigilance is
recommended.

Madden Julian Oscillation MJO
During the warmer months of the year we can anticipate phases of extra
convection in the South Pacific by watching the MJO. This index is NOT
having much impact on tropical convection during the coming week. My future
blogs will give more info about it.

TROPICAL TOPICS
Tropical cyclone activity at present includes ANA which has maintained its
integrity since re-curving wets of Hawaii early last week and is now
unravelling but its components may well reach the Victoria coast of CANADA
this week. There is also a feature currently name 04A FOUR in the Arabian
Sea.

Weekly rain maps show that there was heavier rain in the past week over
Solomons/ northern Coral Sea than in the previous week.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ strengthened in the past week but is expected to weaken and become more
spread out this week, mostly drifting north.

STR= Sub-tropical Ridge
High between Fiji and NZ today is expected to travel steadily eastwards
along 25 to 30S to 150W by Thursday and then to the southeast.
Another HIGH is expected to move form Aussie bight into Tasman Sea on
Wed/Thu and then eastwards along 30S on Fri/sat/sun. This makes for a
strong STR all week.
Another HIGH is in the south Tasman Sea tonight and expected to fade as it
crosses southern/central NZ on Monday. This high is just a break between
the troughs in the Southern Ocean and for the rest of the week the strong
disturbed westerly winds that are typical of spring dominate the Tasman
Sea/NZ pattern.
The ECMWF model (tinyurl.com/ecaus) shows that the STR is likely to spread
southwards on to NZ early next week (4 Nov).

Between the tropics and NZ :
Vessels in the All Points Rally (www.islandcruising.co.nz/?page_id=1687)
are looking for a good weather pattern for sailing to Opua, NZ from Tonga,
Fiji, or Vanuatu. This rally is free of charge (thanks to the sponsors) and
helps participants with planning, weather info, clearance, and seminars on
how to enjoy NZ. I shall do my bit here by commenting on windows of
weather to get to NZ.
The first factor to consider a departure date is the local weather: the
SPCZ does have some convective cloud over northern Vanuatu and parts of Fiji
at present but is not very intense and seems to be likely to drift north and
spread out. It isn't really strong enough to delay departure this week.
The second restraint on a weather window is to pick an ETA over northern
NZ that does NOT have strong adverse winds. Northern NZ is expected to
have strong winds from Monday to Thursday. Then these winds should ease
over the weekend 1-2 Nov and be light and variable early next week 3-4 Nov.
Arranging your trip to reach NZ on 3-4 and maybe 5 Nov looks OK at this
stage. Beyond that is too far away to tell at this stage.

The third factor is to avoid gales and heavy swells during the trip.
Sadly a burst of 3 to 4 metre swell from the southern Ocean moving as far
north as 23S by Friday in area north of NZ. This is in the STR and winds
will be light: no whitecaps, and the swells will have long periods of 11 to
12 seconds, so it is likely to be a gentle encounter. However it may
require a watchful hand on the tiller, and may be uncomfortable.
Anyone wish in avoid sailing in these condition should delay getting to 23S
until after Friday.
Those who intend to go to North Minerva and wait there for a good sailing
window are likely to have an OK wait until Thursday this week , then those 3
metre swells are expected to briefly reach the area (outside the
reef) on local Friday night (in time for Halloween) easing again on
Saturday.
MINERVA REEF
UTC | hPa |Dir kt| m | %
27-Oct-14 0000|1017|088|13|2.1|19
27-Oct-14 0300|1017|093|13|2.0|12
27-Oct-14 0600|1016|092|14|2.0|5
27-Oct-14 0900|1017|087|15|1.9|4
27-Oct-14 1200|1017|085|14|1.9|3
27-Oct-14 1500|1017|087|13|1.8|2
27-Oct-14 1800|1018|092|13|1.7|1
28-Oct-14 0000|1018|098|14|1.6|0
28-Oct-14 0600|1018|108|15|1.6|1
28-Oct-14 1200|1018|102|15|1.6|1
28-Oct-14 1800|1017|104|15|1.5|0
29-Oct-14 0000|1017|093|13|1.5|0
29-Oct-14 0600|1016|087|14|1.4|1
29-Oct-14 1200|1017|056|11|1.4|2
29-Oct-14 1800|1016|036|06|1.3|3
30-Oct-14 0000|1015|092|01|1.3|2
30-Oct-14 0600|1016|150|06|1.2|1
30-Oct-14 1200|1016|118|05|1.2|0
30-Oct-14 1800|1017|124|06|1.3|28
31-Oct-14 0000|1017|132|08|1.6|56
31-Oct-14 0600|1017|130|11|2.5|73
31-Oct-14 1200|1018|103|10|3.0|89
31-Oct-14 1800|1018|114|10|3.0|83
01-Nov-14 0000|1019|121|11|2.8|77
01-Nov-14 0600|1019|119|16|2.5|79
01-Nov-14 1200|1020|107|15|2.4|80
01-Nov-14 1800|1020|114|15|2.2|83
02-Nov-14 0000|1020|114|16|2.3|87
Spot read out at Minerva; hPa is air pressure, Dir kt is wind
direction true and speed in knots, m is wave height in significant metres,
% is cloud cover SO the decision about when to depart depends on these three
factors as well as speed of vessel and crew expectations, and the answer
will be
different for different vessels. Normally at this time of the year
there can be paralysis by over-analysis, especially at the Minerva yacht
club.
The good news is that there are NO gales expected to south of 30S after
Thursday- just that period of enlightened swells to factor in. Next week
could well be different.


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 October 2014

Bob Blog issued 19 Oct 2014

WEATHERGRAM
YOTREPS
Issued 19 October 2014
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.

Background influences
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 standardised difference in the barometer readings between
Tahiti and Darwin.
It has been negative since July and was near to -10 (Australian units)
during September but is now less extreme indicating that the recent trend
towards an El Nino is relaxing.

TROPICAL TOPICS
Tropical cyclone activity at present includes GONZOLA (after its direct hit
with Bermuda) heading for Scotland, and ANA going north to west of Hawaii.
The remains of HUDHUD over India last week caused a storm that brought
unseasonal blizzards to the Himalayas killing more than twenty trampers.

WEATHER ZONES

SPCZ=South Pacific Convergence zone.
SPCZ is expected to strengthen this week and to slowly spread south onto
Fiji from Tuesday, and possibly onto northern Vanuatu and Tonga on Sat/sun
25/26 Oct.
The week starts with a frontal zone attached to a deep low near 30S 155W
(low traveling south), and the north end of this is expected to move east
across French Polynesia FP, turning into a convergence zone over southern FP
by the end of the week.

STR= Sub-tropical Ridge
High over Tasmania on Monday is expected to travel NE across the Tasman Sea
and fade near Norfolk by Friday. Another HIGH is expected to travel south
of 45S past south of Tasmania on Thursday and then travel NE across central
or northern NZ on Sat/Sun 25/26, followed by a trough over northern NZ on
Monday and then a SW flow on Tuesday.

Between the tropics and NZ
Vessels in the All Points Rally are busy preparing for their trip to NZ from
Tonga, Fiji, or Vanuatu, to Opua. This rally (http://www.
islandcruising.co.nz/?page_id=1687) is free of charge (thanks to the
sponsors) and helps participants with planning, weather info, clearance, and
seminars on how to enjoy NZ. I shall do my bit here by commenting on
windows of weather to get to NZ.
The first factor to consider a departure date is the local weather: the
SPCZ is expected to travel south on Fiji from Tuesday and then onto northern
Vanuatu and Tonga around 25/26. Better to depart when the SPCZ is NOT
around.
The second restraint on a weather window is to pick an ETA over northern
NZ that does NOT have strong adverse winds. The table below is a spot
read out for Cape Reinga over northern NZ and things looks good this coming
week except for a passing front on local Tuesday morning around 20
1800UTC. Note that the next front is expected on Mon 27 Oct followed by
SW winds on 28th, so try and reach 30S on 28 Oct and that way you should
avoid the most adverse parts of that front.
CAPE REINGA
UTC |hPa |dir kt | m| %
20-Oct-14 0000|1019|234|13|2.2|0
20-Oct-14 0300|1019|222|14|2.2|1
20-Oct-14 0600|1018|215|18|2.2|2
20-Oct-14 0900|1018|230|15|2.2|3
20-Oct-14 1200|1019|247|16|2.1|5
20-Oct-14 1500|1019|247|19|2.1|39
20-Oct-14 1800|1019|206|22|2.3|74
21-Oct-14 0000|1021|198|20|2.6|54
21-Oct-14 0600|1021|185|21|3.0|21
21-Oct-14 1200|1023|162|15|3.1|21
21-Oct-14 1800|1022|147|13|3.0|23
22-Oct-14 0000|1023|145|08|2.9|23
22-Oct-14 0600|1022|147|06|2.8|7
22-Oct-14 1200|1023|117|03|2.8|2
22-Oct-14 1800|1022|100|03|2.8|47
23-Oct-14 0000|1021|073|02|2.7|76
23-Oct-14 0600|1020|227|03|2.5|68
23-Oct-14 1200|1019|248|06|2.4|60
23-Oct-14 1800|1019|226|11|2.3|53
24-Oct-14 0000|1019|216|13|2.1|45
24-Oct-14 0600|1019|208|12|2.0|70
24-Oct-14 1200|1020|201|09|2.0|94
24-Oct-14 1800|1020|233|10|1.9|78
25-Oct-14 0000|1020|222|10|2.0|61
25-Oct-14 0600|1021|195|10|2.1|31
25-Oct-14 1200|1022|171|09|2.1|1
25-Oct-14 1800|1022|160|05|2.1|1
26-Oct-14 0000|1022|182|05|2.0|2
Spot read out at Cape Reinga; hPa is air pressure, Dir kt is wind
direction true and speed in knots, m is wave height in significant metres,
% is cloud cover The next timing constraint is the middle part. This week
(for sail boats) it is to try and avoid the light variable winds that belong
to the centre of passing Highs in the STR. This is difficult when the STR
is strong and placed across the middle of the route. May be better to wait a
week or two for more wind.
Those who intend to go to North Minerva and wait there for a good sailing
window are likely to have an OK wait this coming week-nothing uncomfortable
is expected at Minerva:
MINERVA REEF
UTC | hPa |Dir kt| m | %
20-Oct-14 0000|1016|089|04|2.5|85
20-Oct-14 0300|1016|117|03|2.5|87
20-Oct-14 0600|1015|144|02|2.5|89
20-Oct-14 0900|1015|163|03|2.4|65
20-Oct-14 1200|1016|170|03|2.4|41
20-Oct-14 1500|1016|180|04|2.4|36
20-Oct-14 1800|1016|164|06|2.3|31
21-Oct-14 0000|1016|140|06|2.2|52
21-Oct-14 0600|1016|139|09|2.1|7
21-Oct-14 1200|1016|137|09|2.0|43
21-Oct-14 1800|1016|139|10|1.9|83
22-Oct-14 0000|1016|133|12|1.9|99
22-Oct-14 0600|1016|133|14|1.8|97
22-Oct-14 1200|1017|123|12|1.8|63
22-Oct-14 1800|1017|126|13|1.7|25
23-Oct-14 0000|1016|103|11|1.8|32
23-Oct-14 0600|1016|102|12|1.9|46
23-Oct-14 1200|1016|084|10|2.0|60
23-Oct-14 1800|1015|096|08|2.0|73
24-Oct-14 0000|1015|114|09|2.0|85
24-Oct-14 0600|1015|113|12|1.9|61
24-Oct-14 1200|1015|109|10|1.9|36
24-Oct-14 1800|1015|121|11|1.8|66
25-Oct-14 0000|1015|124|13|1.7|96
25-Oct-14 0600|1015|120|16|1.7|98
25-Oct-14 1200|1015|113|15|1.7|99
25-Oct-14 1800|1016|118|16|1.8|92
26-Oct-14 0000|1016|123|16|1.8|84
Spot read out at Minerva; hPa is air pressure, Dir kt is wind direction
true and speed in knots, m is wave height in significant metres, % is cloud
cover The front that is expected to be crossing northern NZ on Tuesday is
likely to continue NE and peel off to the east across the Kermadecs on
Wednesday If already at Minerva then may as well wait until after this
front (as it is followed by southerly winds and swell) so wait until late
Wednesday or Thursday before proceeding from Minerva to NZ.

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 October 2014

BOB Blog issued 12 Oct 2014

WEATHERGRAM
YOTREPS
Issued 12 October 2014
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 latest NIWA monthly update for a seasonal outlook for the South Pacific
is going for a continuation of drier than normal conditions over most of the
South Pacific area during the next three months.

Background influences
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 standardised difference in the barometer readings between
Tahiti and Darwin.
It has been negative since July and was near to -10 (Australian units)
during September but is now less extreme indicating that the recent trend
towards an El Nino is now relaxing.

TROPICAL TOPICS
Tropical cyclone activity at present includes Very Severe Cyclone HUDHUD
which has just made landfall over eastern India, VONGFONG which is visiting
Japan, and FAY, a storm in the North Atlantic.
The weekly rain maps show that the heaviest rain is associated with the
tropical cyclones. There has also been some intense rain in the eastern
Coral Sea for the past two weeks.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is expected to weaken this week and be loosely lying from south of
Solomons Islands to between Samoa and Fiji. A few showers associated with a
fading trough are likely over Vanuatu until Monday.

STR= Sub-tropical Ridge
High over northern NZ has managed to arrange just light winds above it and
so is a slow-moving feature and should fade just NE of NZ on Wednesday.
Another HIGH is expected to form over southern NZ on Tuesday and then to
move NE towards 35S 160W, to east of NZ, by end of the week. There is
expected to be a zone of enhanced easterly winds in the tropics and on the
north side of this HIGH-a squash zone.

Departing westwards from Tahiti:
There may be a branch of the SPCZ to avoid over the area especially after
Wednesday.
The squash zone is likely to be mainly south of 25S so should not be too
much of a bother.

Between the tropics and NZ
The vessels associated in the All Points Rally will now be involve in
preparations for their voyage, be it from Tonga, Fiji, or Vanuatu , to
OPUA. The Rally is free of charge (thanks to the sponsors) and helps
participants with planning, weather info, clearance, and seminars on how to
enjoy NZ. See more at www.islandcruising.co.nz/?page_id=1687
and register at www.islandcruising.co.nz/?page_id=1268.
I shall be commenting on windows of weather to get to NZ for these people
here for the next few weeks.
There is a good window for getting to NZ from New Caledonia/Vila/NZ, until
Tuesday anyway. However there is a Low lingering between Tonga and NZ on
Monday/Tuesday so not comfortable to get to NZ from Tonga. As the High that
is forecast to be over NZ this week starts moving off to the east there
should be a northerly flow between it and the next Low that should then be
approaching from the Tasman Sea. This northerly flow can be useful, but the
low itself is no good at all for your voyage. At
present the low or trough is expected to reach NZ on Sun 19/Mon 20 Oct
followed by a brief period of SW winds, then NE winds ahead of a new low.
You can maybe weave between these winds with good timing if you are lucky,
or wait for a better looking pattern.
My choice of weather model for planning purposes is tinyurl.com/ecaus

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 October 2014

BobBlog

WEATHERGRAM
YOTREPS
Issued 5 October 2014
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

8 October eclipse
Many of you will be watching the full moon rise with the setting sun on
Wednesday evening. And there is a lunar eclipse this month as well, so that
a few hours after moon rise you can watch it get shaded by earths shadow.
Eclipse starts at 0817UTC and finishes at 1332UTC, should be compelling
viewing if local clouds keep away .
This eclipse reminds me that when the full tide is in the middle of the
night after the October full moon (and thats around 15 Oct this year) there
may be 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 (then sinking 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 may be in
November rather than October.

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 Im told.

Background influences
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 standardised 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, but is slightly relaxing so far in October.
The amount of heat that is being stored in the sea in the Eastern Equatorial
Pacific has also increased, as measured by the NINO3.4index.
The atmosphere and ocean are in cahoots.

TROPICAL TOPICS
At this time of the year, with the sun directly overhead the 5 to 10S zone ,
we need to be mindful of a phenomenon called Cyclone twinning whereby a
cyclone forming near 5 to 10N in the northern hemisphere seems to influence
the formation a feature of similar size and shape in the southern
hemisphere. This happens reasonably often in the Indian Ocean (see
http://lnk.ie/U9SS/e=bobmcdavitt@hotmail.com/http://www.wunderground.
com/blog/JeffMasters/article.html?entrynum=2402
) and was maybe a factor in
the formation of the infamous cyclone Bebe in the South Pacific in 1972.
There is possibly some twinning occurring with features around 10N and
10S at presentbut no cyclone twinning. Westerly winds near the
equator can be part and parcel of low pressure systems at both 10N and 10S.
And a streamline analysis (from MetService) shows equatorial S/SW winds to
north of Papua New Guinea.
As for Tropical cyclone activity at present we have TC PHANFONE and VONGFONG
in the NW Pacific, and SIMON off the Mexican west coast.
The weekly rain maps show the heaviest rain around 140E and part of it over
western Solomon Islands.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is expected to be active in the zone from Solomon Island across the
Coral Sea to New Caledonia between now and Tuesday, extending across Loyalty
Islands to south of western Fiji on Wednesday and Thursday, easing away on
Friday. There is also a weak convergence zone from northern Tonga to
Southern Cooks and an active trough that is expected to lurk around 140W to
south of 20S from Tuesday until Friday

STR= Sub-tropical Ridge
The High travelling east along 30S from Australia is expected to bring a
brief period of light winds to NZ on Tuesday. The next high is expected to
be in the Australian bight on Wednesday a more summer-like latitude.
This high is expected to travel east along 30/35 across the Tasman Sea on
Thursday/Friday and northern NZ on Sat/Sunday. This provides a very good
weather pattern for anyone wishing to sail southward towards NZ.

Departing westwards from Tahiti:
With just that weak convergence zone to contend with the weather pattern is
looking reasonable for westward travel. Note that towards the end of the
week, a high cell is expected to travel east along 30S - and there is likely
to be a zone of enhanced SE trade winds on its northern side, especially
along 20S.

Between the tropics and NZ
With the prospect of a high crossing northern New Zealand next weekend, this
implies and good weather pattern for setting sail to NZ over next few days.
However a departure from Tonga /Fiji/ on Monday to Wednesday or from Noumea
on Monday/Tuesday, is likely to start off with strong SE winds.
SO it is a mixed week.
Note that fronts with squall winds are expected to affect North Island on
Monday and Wednesday.

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.

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