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

28 August 2016

Bob Blog 28 Aug

WEATHERGRAM
YOTREPS
Issued 28 August 2016
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.

SOI The Southern Oscillation Index SOI 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.

SOI (30 day running mean) remains in neutral territory. Its 30-day running mean
is in the 1 to 9 units area on the Australian scale. SOI trend (x10) since 2013
showing us in neutral territory is seen at
www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi

The Ocean: The warmer the sea the quicker it evaporates, tossing water vapour
into the air, where is rises and cools into cloud. The equatorial Pacific region
hosts the widest and warmest sea on the planet. Thus its sea surface
temperatures SST may be thought of as a factor in the running of planetary
weather engine. When SST in the target zone (equatorial Pacific between dateline
and Galapagos) are notably cooler than normal, this is called a La Nina episode.

Sea surface temperature anomaly may be seen at
www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=nino34&p=monthly shows
that we now have cooling seas in the target area, and there MAY be a weak La
Nina in the next few months

The Tropics
TC LIONROCK is in the NW Pacific, TC MADELINE may reach Hawaii next weekend,
(LESTER, further east is fading) and TC GASTON is expected to turn around mid -
Atlantic. There are also two possible tropical lows, labelled GENESIS in track
map atruc.noaa.gov/tracks/, which may affect eastern coast USA this week.

Rain activity is generally weakening except for a few spots in the Indian Ocean
and around Japan.
Rain for the past fortnight from
trmm.gsfc.nasals.gov/trmm_rain/Events/big_global_accumulation.gif

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ this week is expected to slowly develop from Solomon Islands to north of
Fiji area.

STR
HIGH is expected to travel east slowly across the Tasman Sea and then across to
east of NZ on Father's Day weekends (3 to 4 September).
There is expected to be a weak squash zone of enhanced easterly winds on the
north side of this HIGH between Sat 3 and Mon 5 Sep. May as well watch this HIGH
for departure/arrival.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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.

21 August 2016

Bob Blog 21 Aug

WEATHERGRAM
YOTREPS
Issued 21 August 2016
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.

I have been informed of another blog about navigating in the Pacific by
downloading Google earth, BING, and some other maps and viewing them offline.
See www.zero2sixty.ch/navigate-the-pacific-despite-the-bad-charts
This blog is from Art of SV Feeling Good, and gives the link to a program/Ap
called OVITALMAP which can be downloaded to iPad, Android or Windows. It comes
from China but has reasonable English. It doesn't get around the lacunae which
occurs on Google earth and Bing, but does allow you to download the data for
offline viewing.
I have shared this on my Facebook page.

If you are in Fiji tomorrow remember that the whole nation is having a public
holiday to help congratulate their rugby sevens team for winning a gold medal in
the Olympics.

The Tropics
That tropical low which went inland from the Gulf of Mexico and flooded
Louisiana in the past week was a "Hurricane without high winds". In this
changing planet, these beasts seem to be happening more frequently than in the
past century or more, and may need a system to help with warning the public.
An interesting article on this can be read at
medium.com/the-weather-channel/imagine-a-world-without-tropical-depressions-bbc4
840834da#.fut667n0b

And an explanation of why it happened is at
weather.com/storms/severe/news/louisiana-flooding-why-it-happened-things-to-know
Over in Asia the monsoon, now in its last month, has had a fling in India, with
over 30 deaths in the last few days. It has been a wetter than normal monsoon
overall so far.
As seen at apdrc.soest.hawaii.edu/projects/monsoon/realtime-monidx.html

Busy at present in the NW Pacific with cyclones having a party around Japan:
KOMPASU, LIONROCK and MINDULLE
Elsewhere we have a decaying FIONA in the Atlantic:
And we are now up to K for KAY west of Mexico:

The rain maps for the past weeks (see
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif) shows a build-up
of convective activity in the Asian Monsoon and in the SW Pacific for
Vanuatu/Fiji/Tonga ( A visit form the SPCZ, now fading).

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ has faded over Fiji and Tonga during the weekend and is expected to
redevelop over Samoa to east of Niue around mid-week, then fade away by weekend.

Should cross the Tahiti area around Fri 26/Sat 27 August local.

This week's SPCZ may be seen on windyty.com with rain accumulation and six days,
from Windyty.com, using ECMWF data

STR= Sub-tropical Ridge
HIGH east of South Island tonight is moving off to the East. Another High cell
is expected to travel east along 30/40s from Northland area on Monday to south
of French Polynesia next weekend.

Voyage Outlooks:
Tahiti to the west
There is likely to be as quash zone of enhanced trade winds between French
Polynesia and Vava'u from Tue to Sat/Sun 27/28 August local. Avoid.

Between NZ and the tropics
Weak trough is expected to cross northern NZ on Monday.
A series of fronts, some with strong winds, are expected to affect Northern NZ
from late Wed to around Sun 28 August. If you are quick and keen then TUESDAY
is the day to depart.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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.

14 August 2016

BOB's Blog

WEATHERGRAM
YOTREPS
Issued 14 August 2016

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.

For more stories about the work that SEA MERCY has been doing in Fiji since
Cyclone WINSTON see seamercyupdates.blogspot.co.nz
Including the new mural at Makogai School, an article in Yachting World
Magazine, and the arrival of their new landing craft in the Lau group.

Also there is an interesting blog at
nimrodcat.blogspot.com.au/2016/06/navigating-in-pacific-around-coral.html . The
writer, David Straton on NIMROD spotted how
1) Some reefs are positioned in the wrong place on some electronic and paper
charts
2) Google Earth's maps can help show some of these discrepancies.
3) Google Earth doesn't show all the reefs, suffers from lacunae.

To illustrate this last remark check the reefs north of Bligh water – the
stretch of sea between Viti and Vanua Levu in Fiji on your e or paper charts and
on Google earth. The comparison shows that Google earth only decided to show
detail around Charybdis Reef and Yadua Island, and the remainder is … lacunae.
Bligh would not have been impressed.

David's blog shows an illustration of this problem in Tonga AND adds a link to a
kmz file which adds 60 waypoints for missing/dangerous Tongan reefs to your
Google Earth (it's a Dropbox link and you should be able to download without
joining Dropbox if you wish by selecting "download only") see
www.dropbox.com/s/c1f3vpz4vjqjsvd/Uncharted%20Reefs.kmz

The Tropics
During WWII the bombers based at Mariana Islands would fly bombing raids using
high Altitude B-29 aircraft. This was an interesting learning curve
meteorologically…. We didn't know much about Jet Streams until these pilots
encountered them. Also it was a surprise to the USA flying crew that the
cyclones in NW Pacific run at a frequency of one a week. These crew got little
sleep in-between missions and soon got into a déjà vu-itis confusing one storm
with another. To help the flying crew keep track, the meteorologists started
naming the storm using the phonetic alphabet (Alpha Bravo etc.). This wasn't the
first time storms were named… that started in Australia in the 1890s thanks to
Clement Wragge.

I raise this point because this week we have two cyclones in the NW Pacific
CONSON (08W) and CHANTHU (09W) both named by JMA … it would have been
interesting if two C-named cyclones were coexisting in the mid-1940s.
CONSON and CHANTHU tracks may be seen at www.tropicaltidbits.com/storminfo

The rain maps for the past weeks, from
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif , shows a
build-up of convective activity over NW Pacific and around the Solomon Islands.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is active this week and stretching from Solomon islands across Northern
Vanuatu and Southern Fiji to the Minerva area. A LOW is expected to form south
of French Polynesia by mid-week and its associated trough should bring variable
winds to Tahiti. This week's SPCZ may be seen on windyty.com with rain
accumulation set to ten days.

STR= Sub-tropical Ridge
HIGH crossing Tasman Sea is expected to travel across South Island by mid-week
and then build to east of South Island and over Chatham Islands until
mid-next-week, maybe rising to 1040 hPa, making it a Big Fat High (BFH).
Squash Zone: As this HIGH crosses the Tasman Sea on Mon to Wednesday, there
should be a squash zone of enhanced trade winds in the Coral Sea/New Caledonia/
Southern Vanuatu to Fiji area on the north side of this HIGH.

Voyage Outlooks:
Tahiti to the west
The data is showing a mostly dry week around Tahiti and OK winds for departure
until at least Sat 20 local. Any voyage to the west will need to sail around at
least one passing trough which may contain squalls, but this week seems to be
free of any squash zone as far west as Tonga. Looks best to go along 18S.

Between NZ and the tropics
A Low is expected to form over northern NZ on Monday and deepen as it travels
east along 35S—so later this week there should be an intense squash zone between
this low and the BFH over Chathams. This squash zone is likely to toss a lot of
swell onto NE coast of NZ after Wednesday. These swells may have a long period,
so if they are OK and the SE/easterly winds along the NE coast of NZ (after
Tuesday) are OK then a departure from NZ to the north is 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.

07 August 2016

Bob Blog 7 August 2016

WEATHERGRAM
YOTREPS
Issued 7 August 2016

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.
Weather patterns for the past month:

Averaged weather maps for July may be seen at
www.esrl.noaa.gov/psd/map/images/fnl/slp_30.fnl.anim.html
and pressure anomaly map for last month from
www.esrl.noaa.gov/psd/map/images/fnl/slp_30a.fnl.anim.html

These maps show that during July the weather pattern over the South Pacific
changed from a HIGH to NE of NZ to a stronger than normal disturbed westerly
flow. And there are a pair of amplified HIGHS either side of North America,
aiding bushfires.
And the Indian Ocean weather patterns are completely different from those in the
South Pacific.

The Tropics
TC HOWARD was named on Monday, peaked of Tuesday and its remnants got close to
Hawaii by Sunday (local).
see
www.staradvertiser.com/breaking-news/rain-expected-as-tropical-storm-howard-move
s-closer-to-hawaii/

TC IVETTE has now been named today near 137W and may affect Hawaii area from
local Thursday, but, like HOWARD, is expected to weaken as it approaches.
There is another tropical low near the Mexico coast approaching Baja California.

In the NW Pacific, OMAIS is aiming to travel north along the East coast of
Japan.
And another system is likely to form near 20N 160E on Monday.

The rain maps for the past weeks from
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif shows a build-up
of convective activity over NW Pacific, and a drop in activity in the South
Pacific.


WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is weak this week and expected to remain draped over North Coral Sea and
from Tuvalu to Tokelau to Northern Cooks. There is a passing trough tonight over
Fiji (bringing rain, welcomed by some) and this should travel off to the
southeast by mid-week.

STR= Sub-tropical Ridge
Next HIGH is travelling along 50S on Mon/Tuesday towards South island on
Wednesday and then to east northeast of NZ crossing Chatham Islands on Thursday.
Since this week's HIGH is coming from so far south it has brought chilled air to
the South Island - at around the time of the year we get our coldest
temperatures.
The following HIGH next week is expected to take a more regular course along
35S.

Voyage Outlooks:

Tahiti to the west
Maybe some showers around Tahiti on local Sunday/Monday, then looks to be more
settled for the remainder of the week for departure. Wind flow is looking good
for getting west this week, but a passing trough is likely to being variable
winds south of 20S especially after Wednesday.

Between NZ and the tropics
Meteorologists has a phrase to describe this pattern, one that seems to pop up
mid-winter --- "LOW INDEX" the means that the zonal index, as measured by the
baro pressure at Auckland minus that an Invercargill (usually a positive number)
is taking on negative values, with Highs over the South Island and lows over the
North Island.

This changes the strategy for departing from northern NZ. The best looking
opportunity is today or Monday. Monday is a day of light variable winds
in-between the Low that moved off northern NZ last night and another low that is
expected to do so on Tuesday/Wednesday. So a departure on Monday takes a voyage
deliberately across the centre of a low-where the winds are light and variable,
but somewhat unsteady, and where there may be rain clouds and perhaps a squall.

If you wait until Tuesday or later then the outlook is for onshore winds and
swell-not such a good idea for departure.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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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