Translator

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

27 April 2014

Bob's Blog issued 27 April 2014

WEATHERGRAM
YOTREPS
Issued 27 April 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 of weather maps, so please fine-tune to your place.
Dates are in UTC unless otherwise stated.

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) was in the pink (below minus 10 in the
farmonlineweather.com graph for much of April but is now blue again.

TROPICAL TOPICS
No tropical cyclones around tonight, but the International Tropical
Convergence zone has been active across the entire Pacific and over Central
America. Also there was an almost-cyclone that brought a period of wind and
rain to Gulf of Carpentaria and threatened the Timor Sea.

The recent deadly avalanches on Everest are noteworthy. The glacial melt
lakes in that region have been growing since the 1980s. Most (but not
all) glaciers in the region are shrinking because of a drop off in regional
rains during the monsoon and winter months. Apa Sherpa used to have a farm
until it was claimed by a glacial lake outburst flood in 1985 and then he
became a climbing guide. According to Apa: In 1989 when I climbed Everest
there was a lot of snow and ice, but now most of it has just become bare
rock.

WEATHER ZONES

Panama to Galapagos: The wind flow over Panama and Las Perlas is expected to
be light and variable over the next few days. Also the wind flow for much of
the distance between Panama and Galapagos is expected to be from the SW this
week, as was the case last week, no good for this voyage. And so it may be
worthwhile waiting another week (or more) for this trip, sad to say.

Galapagos to Marquesas
If departing in the next few days with a vessel cruising at up to 6 knots
then head off to south of the direct path at the start along 244M/248T to
2deg 30min S then WSW along 250M/262T for around 1888nm then go direct to
Fatu Hiva.

SPCZ South Pacific Convergence Zone
This stretches from Solomons to Fiji. There is also a convergence zone from
Tonga/Samoa to French Polynesia, found on the north end of the squash zone
of enhanced trade winds and NE winds that mark the north end of a large
intense High with centre near 45S.
A tropical LOW may form south of Tonga by Wednesday 30 April and travel
south along 170W.

STR Sub-tropical Ridge
The STR remains in its normal winter position, stretching from the deserts
of inland Australia across the North Tasman Sea and generally along 35 to
45S to the east of NZ.

New Zealand area
A front is on its way to cross Northland on Monday and then a squally trough
is expected on Tuesday.
This is followed by a W/SW flow on Wednesdaythe best weather pattern for
departing to the north this week, and then a passing high with light winds
on Thursday.
A large trough/low is expected to deepen rapidly off Tasmania on Saturday
3 May and then cross the Tasman Sea /NZ area early next week. The NW flow
ahead of this system should start over Northland from Friday.

Departing from NZ to the tropics
30 April is the nominal end of the Southern Hemisphere Cyclone season so
many yachts may want to depart Northland then or in early May. It seems to
me that the best day to depart this week is with the W/SW winds on
Wednesday.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe. Weathergram text only (and translator) is at
weathergram.blogspot.co.nz My website is at metbob.com - To unsubscribe,
send a reply email saying unsubscribe. Feedback to bob@metbob.com

20 April 2014

Bob's Blog 20 April 2014

WEATHERGRAM
YOTREPS
Issued 20 April 2014: Easter Sunday
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 of weather maps, so please fine-tune to your place.
Dates are in UTC unless otherwise stated.

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) has been in the pink (below minus 10 in the
farmonlineweather.com graph for three weeks and relaxed a lot in the past
two weeks.

TROPICAL TOPICS
Tropical Cyclone ITA weakened quickly to Cat 1 over Queensland and then
re-deepened from 1000 to 980 hPa as it moved south along west coast of NZ on
Thursday to Saturdayas expected and mentioned in last weeks Weathergram.
The wind and rain damage for the start in Easter in NZ has been substantial.
In the Indian Ocean a tropical Low is possibly intensifying and is expected
to head SE perhaps towards the MH370 missing aircraft search area later this
week, but is expected to fade away before it gets there.

WEATHER ZONES
Panama to Galapagos: The wind flow over Panama and Las Perlas is expected to
be light and variable over the next few days. Also the wind flow for much of
the distance between Panama and Galapagos is expected to be form the SW this
week, no good for this voyage. And so it may be worthwhile waiting another
week (or more) for this trip, sad to say.

SPCZ South Pacific Convergence Zone
This is rather disjointed this week and rebuilding along the northern end of
its range from Solomons to Samoa.
A tropical LOW may form over Solomons by Wednesday and travel slowly SW into
the Coral Sea by the weekend, perhaps this may allow a trough to form over
Vanuatu and New Caledonia next week.

STR Sub-tropical Ridge
The STR has now shifted to its normal winter position, stretching from the
deserts of inland Australia across the North Tasman Sea and generally along
35 to 25S to the east of NZ. I'm not sure how long this pattern will last,
but it is the normal winter pattern, and if an El Nino episode kicks in then
it is the preferred pattern for the next few months.

New Zealand area
Trough is moving off to the east of NZ on Easter Monday.
HIGH in the north Tasman Sea is expected to move across the north of the
North Island on Wednesday/Thursday. A trough should cross the North Island
on Friday (ANZAC DAY)/Saturday, followed by another High travelling along
40S on Saturday/Sunday.
This is a good weather pattern for travel between NZ and the tropics to the
north, or vice versa. Enjoy!
However anyone attempting to sail across the Tasman Sea will need to be
watchful of large areas of light and variable wind. The SOLO TRANS TASMAN
YACHT RACE is departing from New Plymouth for Mooloolaba on Tuesday, so we
wish them well.

From Easter, the Double Ditch campaign has started with a kiwi attempting to
take a kayak from Coffs Harbour in Australia to New Plymouth in the NZ.
MetBob is helping with this adventure and you can follow its progress at
http://doubleditch.co.nz/tracking

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe. Weathergram text only (and translator) is at
weathergram.blogspot.co.nz My website is at metbob.com - To unsubscribe,
send a reply email saying unsubscribe. Feedback to bob@metbob.com

13 April 2014

Bob's Blog 13 April

WEATHERGRAM
YOTREPS
Issued 13 April 2014
Bob McDavitts ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world of weather maps, so please fine-tune to your place.
Dates are in UTC unless otherwise stated.

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) has been in the pink (below minus 10 in the
farmonlineweather.com graph for three weeks and relaxed a little in the past
week.

TROPICAL TOPICS
Tropical Cyclone ITA is visiting the Queensland coast at present and is
expected to move SE towards the North Island by Wednesday and to then travel
south and merge with another low on Thursday/Friday and cross the South
Island on Easter Saturday/Sunday.
In the NW Pacific, ex Tropical Cyclone PEIPAH (DOMENG) has been approaching
central east Philippines over the past few days, but this system is
weakening.

WEATHER ZONES
Panama to Galapagos: There is a NE flow over Las Perlas at present but a
departure now is likely to run into light variable winds in a day or so.
Light and variable winds are expected to dominate proceedings between Panama
and 4N from local Monday until the end of this week.

SPCZ South Pacific Convergence Zone
This is rather disjointed this week and appearing as two distinct zones,
with one around the Solomons and another roughly from Niue to French
Polynesia.
There is still a weak convergence zone along around 5S from around 100 to
130W.

STR Sub-tropical Ridge
The STR is around 40S, its normal location at this time of the year. It has
been knocked out of the Tasman Sea for the first time in around eight weeks.
This should finally allow rain to reach the drier parts of NZ this week.

New Zealand area
There is a Low moving slowly south in the Tasman Sea and its warm front is
expected to bring some rain to New Zealand on Monday. By Wednesday ITA
should have left the tropics and moved SE to be close to the west of the
North Island. During Thursday and Friday this system might re- intensify ;
its central pressure might drop from around 1000 to around 980 hPa, due, I
think, to the density difference between the air it is bringing from
Queensland and the cold air being directed northwards by that other low in
the South Tasman Sea.
This means that a front with gale NE to weaker northerly winds is likely for
the Auckland to Tauranga race this year.
This system is expected to cross the South island during Easter Saturday and
Sunday.
This means that the likely weather pattern for the start of the Solo
Trans-Tasman Race on Easter Sunday is a left-over trough (or two) and then
light winds in a new STR

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe. Weathergram text only (and translator) is at
weathergram.blogspot.co.nz My website is at metbob.com  To unsubscribe,
send a reply email saying unsubscribe. Feedback to bob@metbob.com

06 April 2014

Bob's Blog issued 6 April 2014

WEATHERGRAM
YOTREPS
Issued 06 April 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 of weather maps, so please fine-tune to your place.
Dates are in UTC unless otherwise stated.

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) has been in the pink (below minus 10 in the
farmonlineweather.com graph for the past three weeks. One more week and we
can start calling this the beginning of a new El Nino episode.

Sea Surface temperatures
The warmer the sea, the faster it evaporates water into the atmosphere and
this is what helps weather (cloud and rain) to form. Areas of sea that are
warmer than normal (positive anomalies) are breeding grounds for tempestuous
weather.

Recently the sea surface temperatures in the target area (the equatorial
Pacific between 180 and Galapagos) has warmed to a slight positive anomaly.

TROPICAL TOPICS
During March the Sub tropical ridge (STR) became stronger than normal across
the South Pacific along 40 to 50S. This knocked the westerlies of the
roaring 40s well to the south and also managed to shield NZ from the fronts
it normally gets. This pattern is NOT expected to continue, and by the end
of April, after Easter, the fronts should become more noticeable especially
over the South Island.
The clouds that brought the rain that hit the Solomons (see
http://wp.me/p2CxPj-hp) have now congealed to make up Tropical Cyclone ITA
in the Coral Sea. At this stage the future track of ITA is difficult to
deduce. The GFS ensemble is picking it may re-curve into the Tasman Sea but
the Canadian model is picking it should go west into the Gulf of
Carpentaria.
If you are in the region then keep watching.

WEATHER ZONES
Panama to Galapagos: There are mainly light and variable winds between now
and Thursday 10 April, then there may be sufficient NE winds to allow a good
enough voyage from Friday.

SPCZ South Pacific Convergence Zone
This is rather disjointed this week and appearing as two distinct zones,
with one from Coral Sea to Loyalty Islands and another from east of Solomons
to Fiji area, spreading to Tonga late in the week.
There is still a weak convergence zone along around 5S from around 100 to
170W.

STR Sub-tropical Ridge
The STR continues to be strong between 40 and 50S, well south of its normal
position.
This is so far south that there is room for lows to form in the sub-
tropics, and one of these is forecast to form to SE of Pitcairn Island by
Wednesday 9 April, traveling away to the SE.

New Zealand area
The squally Low that hit Rarotonga last Sunday night (NZ Date) (see
http://wp.me/p2CxPj-hj) has been moving to the SW for the last week and is
now moving SSW along the east coast of the North island. This abnormal track
is associated with the strong STR. The warm air associated with the Low
brought air temperatures up to 28 in the North Island today, a new April
record.
This low and a front that has stalled in the Tasman Sea are both expected to
fade over the North Island area whilst a HIGH cell moves east across the
South Island mid-to-late week.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe. Weathergram text only (and translator) is at
weathergram.blogspot.co.nz My website is at metbob.com - To unsubscribe,
send a reply email saying unsubscribe. Feedback to bob@metbob.com

Blog Archive