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.
Compiled Sunday 25 February 2024
Panama to Marquesas -seasonal challenges
Normally the International Convergence zone ITCZ meanders across the
Pacific Ocean in a latitude band between 10 and 2 degrees north of the
equator.
An interesting "mirror" of the ITCZ forms in the eastern Pacific at
this time of the year:
This is triggered by the overhead sun. During late February and early
March, the latitude of the overhead sun shifts slowly northwards from
11S (20Feb) towards the equator (21 Mar/equinox) and then Panama (10
April) (see table of solar declination)
This triggers a convergence zone to southwest of the Galapagos which
lingers there maybe until April, then disappears until the following
year. I call this the mirror convergence zone as it seems to somehow
mirror what is happening in the ITCZ to the north. That could be due
to the way the atmospheric currents turnover with zones of two
castling clouds sharing the same moat of sinking air.
This will become one of the challenges for vessels sailing between
Panama and Marquesas. Another challenge is that as the season changes
the southerly winds in the southern hemisphere will shift north, and
NE winds in the Panama gulf will gradually fade by early April when
the overhead sun gets north of Panama. The swells between Panama and
Galapagos become a confused amalgam but with an increasing SW
component.
One feature that is useful for sailors entering the Pacific from
Panama is the sea surface current.
I know we still have an EL NINO episode, but this is fading. EL NINO
is associated with a weaking of the equatorial west-going current, but
at present this current is looking very healthy. These currents are
taking the warmer-than-normal sea surface that EL NINO built up near
Galapagos out into the rest of the Pacific.
TROPICS
l Cyclone Potential
Northwestern Australia was drenched by slowly moving Tropical Storm
Lincoln. The storm strengthened after moving out to sea again, and
then made landfall on the far northwest coast. Tropical Storm Eleanor
looped around the Indian Ocean islands of Mauritius and Réunion. There
is still a potential for development over Vanuatu but this is
decreasing.
WEATHER ZONES
The South Pacific Convergence zone remains well established from
Vanuatu to Low L3 which is expected to travel off to the southeast.
There is another convergence zone over Northern Cooks, and tropical
low L2 south of Southern Cooks that should linger until mid-week then
fade.
There is also a convergence zone lingering south of Tahiti.
HIGHS and LOWS
HIGH H1 continues to linger well east of NZ.
Low L3 formed northwest of Auckland today, disrupting an Australian
/NZ cricket game. It is expected to deepen further as it moves
southeast, crossing Chathams mid-week. It should leave a southerly
flow over NZ until Wednesday.
HIGH H2 in Australia Bight should cross Tasmania on Monday and then
move northeast across the Tasman Sea reaching 30S to north of NZ by
Friday, followed by a trough over NZ this weekend.
Panama to Marquesas: the Northerly winds in the gulf should last all
week. Scattered squalls between 5N and 2N.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about your voyage, then check
metbob.com to see what I offer.
Or Facebook at /www.facebook.com/metbobnz/
Weathergram with graphics is at metbob.wordpress.com
(subscribe/unsubscribe at bottom).
Weathergram archive (with translator) is at
weathergram.blogspot.co.nz.
Contact is bob@metbob.com or text 64277762212.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
25 February 2024
18 February 2024
Bobgram 18 Feb
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.
Compiled Sunday 18 February 2024
El Nino is expected to weaken this autumn
We are having an El Nino weather pattern. It is the name given to the
period when sea surface temperatures over the eastern equatorial
Pacific are above normal. This pattern is expected to weaken during
our autumn as shown by The Bureau of Meteorology, Australia. with the
trends in Sea temperature made by several computer models.
The next image in my illustrated edition at metbob.com shows the daily
averaged isobars over the NZ area for the main part of summer
(longitudes 160E to 180 and latitudes 20S to 50S from Dec 1st to Feb
15th). The passing HIGHS are regular around once a week but for late
January and early February South of the Highs there are regular
passing fronts and lows crossing the Southern Ocean bringing rain to
the southwest of NZ and hot dry northwest winds to places east of the
main ranges.
As we move out of El Nino during autumn there is likely to be a period
where the weather will swing from one pattern to another, allowing
variety as each pattern gets to "play" for a short time. I call this
"weather Jazz" and at metbob.com is what I got when I asked AI to draw
that.
TROPICS
An unnamed, short-lived and minimal tropical storm drenched central
parts of the Vanuatu archipelago before dissipating near Fiji. Another
tropical depression recently drenched the Sothern Coos and is now
moving off to the southeast. LINCOLN moved from Gulf of Carpinteria to
inland Australia, And GYOUNGOU is in the mid Indian Ocean.
WEATHER ZONES
The South Pacific Convergence zone remains strong, active, squally and
has a few tropical depressions, but there is too much wind shear aloft
to allow cyclones to form.
L1 near Samoa is expected to start moving to the southeast across Niue
area and the Southern Cooks after Wednesday.
L2 has been hovering to west of Fiji for a few days and will do so
until around Wednesday then weaken.
HIGHS and LOWS
HIGH H1 east of NZ should weaken as it travels further east.
Front attached to L3 is expected to quickly cross NZ on Monday.
H2 is expected to cross the Tasmanian area tonight/ then the central
Tasman Sea on Monday/Tuesday
and then central NZ on Wednesday and Thursday with a ridge remaining
in the far north as the High travels off further east.
After H2 a frontal trough is expected to reach the South Island by
Saturday and cross the North Island on Sunday25 Feb.
Panama to Marquesas: the Northerly winds in the gulf should last all
week. Scattered squalls to 2S.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about your voyage, then check
metbob.com to see what I offer.
Or Facebook at /www.facebook.com/metbobnz/
Weathergram with graphics is at metbob.wordpress.com
(subscribe/unsubscribe at bottom).
Weathergram archive (with translator) is at
weathergram.blogspot.co.nz.
Contact is bob@metbob.com or text 64277762212.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Disclaimer: Weather is a mix of pattern and chaos; these ideas are
from the patterned world.
Compiled Sunday 18 February 2024
El Nino is expected to weaken this autumn
We are having an El Nino weather pattern. It is the name given to the
period when sea surface temperatures over the eastern equatorial
Pacific are above normal. This pattern is expected to weaken during
our autumn as shown by The Bureau of Meteorology, Australia. with the
trends in Sea temperature made by several computer models.
The next image in my illustrated edition at metbob.com shows the daily
averaged isobars over the NZ area for the main part of summer
(longitudes 160E to 180 and latitudes 20S to 50S from Dec 1st to Feb
15th). The passing HIGHS are regular around once a week but for late
January and early February South of the Highs there are regular
passing fronts and lows crossing the Southern Ocean bringing rain to
the southwest of NZ and hot dry northwest winds to places east of the
main ranges.
As we move out of El Nino during autumn there is likely to be a period
where the weather will swing from one pattern to another, allowing
variety as each pattern gets to "play" for a short time. I call this
"weather Jazz" and at metbob.com is what I got when I asked AI to draw
that.
TROPICS
An unnamed, short-lived and minimal tropical storm drenched central
parts of the Vanuatu archipelago before dissipating near Fiji. Another
tropical depression recently drenched the Sothern Coos and is now
moving off to the southeast. LINCOLN moved from Gulf of Carpinteria to
inland Australia, And GYOUNGOU is in the mid Indian Ocean.
WEATHER ZONES
The South Pacific Convergence zone remains strong, active, squally and
has a few tropical depressions, but there is too much wind shear aloft
to allow cyclones to form.
L1 near Samoa is expected to start moving to the southeast across Niue
area and the Southern Cooks after Wednesday.
L2 has been hovering to west of Fiji for a few days and will do so
until around Wednesday then weaken.
HIGHS and LOWS
HIGH H1 east of NZ should weaken as it travels further east.
Front attached to L3 is expected to quickly cross NZ on Monday.
H2 is expected to cross the Tasmanian area tonight/ then the central
Tasman Sea on Monday/Tuesday
and then central NZ on Wednesday and Thursday with a ridge remaining
in the far north as the High travels off further east.
After H2 a frontal trough is expected to reach the South Island by
Saturday and cross the North Island on Sunday25 Feb.
Panama to Marquesas: the Northerly winds in the gulf should last all
week. Scattered squalls to 2S.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about your voyage, then check
metbob.com to see what I offer.
Or Facebook at /www.facebook.com/metbobnz/
Weathergram with graphics is at metbob.wordpress.com
(subscribe/unsubscribe at bottom).
Weathergram archive (with translator) is at
weathergram.blogspot.co.nz.
Contact is bob@metbob.com or text 64277762212.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
11 February 2024
Bob Blog
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.
Compiled Sunday 11 February 2024
SUBTROPICAL RIDGE
Occasional in summer we get today's wonderful pattern when the MJO takes the Monsoonal trough out from Australia and into the central Pacific:
During an El Nino period this helps feed the Hadley and Walker circulations to intensify the Subtropical ridges
I often mention how we can work out the rhythm of weather in the South Pacific by watching the Subtropical ridge STR Recently I have encountered a paper from the boffins at CSIRO in Tasmania who are watching the STR as a way to calculate likely rainfall trends in SE Aus. They have introduced parameters to measure the STR along their local longitude near 150E STR-I for Intensity (hPa) and STR-P for position (Latitude).
www.cawcr.gov.au/projects/vicci/wp-content/uploads/2015/11/Grose2.pdf
Their investigations show that the STR is usually at its southern -most latitude of 38S in February with an average isobar of 1015. Their modelling shows that in the next few decades it is expected to remain close to this positional cycle (with a nudge poleward) but increase its intensity.... Thereby, as a rule of thumb, reducing the rainfall and increasing the surrounding winds.
TROPICS
As expected, it has been a busy week in the South Pacific
Cyclone Nat skirted parts of French Polynesia after forming to the east of American Samoa.
Tropical Storm Osai also formed near Samoa but drifted southeast toward the Cook Islands and unwound.
The Tropical depression now S of Fiji (12P/05F) may blossom into cyclone if it shifts to Samoa
but then enters an area of strong winds aloft that will likely help it unravel.
The Radiosonde from Nadi airport (as seen on Windy) shows these strong winds:
This vertical cross section of the atmosphere (done by good olde weather balloon)
shows very warm moist and unstable air in the dangerous Quadrant of that Low.
WEATHER ZONES
The South Pacific Convergence zone is strong, active, squally and still breeding tropical depressions,
but there may be too much wind shear aloft to allow cyclones to form. L1 southeast of Tahiti is moving off.
L2 near Fiji is the main feature to watch and may still blossom into a cyclone near Samoa mid-week.
HIGHS and LOWS
East of NZ the STR reigns, with a squash zone of enhanced easterlies near 30S.
Over NZ, a cool dying southerly flow on Monday
then a passing HIGH Tuesday to Thursday,
followed by a fading front reaching Southland late Thursday
and Chatham Islands on Saturday.
Panama to Marquesas: the Northerly winds in the gulf may fade on Tuesday and again this weekend.
Avoid departing then.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about your voyage, then check metbob.com to see what I offer.
Or Facebook at /www.facebook.com/metbobnz/
Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom).
Weathergram archive (with translator) is at weathergram.blogspot.co.nz.
Contact is bob@metbob.com or text 64277762212.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.
Compiled Sunday 11 February 2024
SUBTROPICAL RIDGE
Occasional in summer we get today's wonderful pattern when the MJO takes the Monsoonal trough out from Australia and into the central Pacific:
During an El Nino period this helps feed the Hadley and Walker circulations to intensify the Subtropical ridges
I often mention how we can work out the rhythm of weather in the South Pacific by watching the Subtropical ridge STR Recently I have encountered a paper from the boffins at CSIRO in Tasmania who are watching the STR as a way to calculate likely rainfall trends in SE Aus. They have introduced parameters to measure the STR along their local longitude near 150E STR-I for Intensity (hPa) and STR-P for position (Latitude).
www.cawcr.gov.au/projects/vicci/wp-content/uploads/2015/11/Grose2.pdf
Their investigations show that the STR is usually at its southern -most latitude of 38S in February with an average isobar of 1015. Their modelling shows that in the next few decades it is expected to remain close to this positional cycle (with a nudge poleward) but increase its intensity.... Thereby, as a rule of thumb, reducing the rainfall and increasing the surrounding winds.
TROPICS
As expected, it has been a busy week in the South Pacific
Cyclone Nat skirted parts of French Polynesia after forming to the east of American Samoa.
Tropical Storm Osai also formed near Samoa but drifted southeast toward the Cook Islands and unwound.
The Tropical depression now S of Fiji (12P/05F) may blossom into cyclone if it shifts to Samoa
but then enters an area of strong winds aloft that will likely help it unravel.
The Radiosonde from Nadi airport (as seen on Windy) shows these strong winds:
This vertical cross section of the atmosphere (done by good olde weather balloon)
shows very warm moist and unstable air in the dangerous Quadrant of that Low.
WEATHER ZONES
The South Pacific Convergence zone is strong, active, squally and still breeding tropical depressions,
but there may be too much wind shear aloft to allow cyclones to form. L1 southeast of Tahiti is moving off.
L2 near Fiji is the main feature to watch and may still blossom into a cyclone near Samoa mid-week.
HIGHS and LOWS
East of NZ the STR reigns, with a squash zone of enhanced easterlies near 30S.
Over NZ, a cool dying southerly flow on Monday
then a passing HIGH Tuesday to Thursday,
followed by a fading front reaching Southland late Thursday
and Chatham Islands on Saturday.
Panama to Marquesas: the Northerly winds in the gulf may fade on Tuesday and again this weekend.
Avoid departing then.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about your voyage, then check metbob.com to see what I offer.
Or Facebook at /www.facebook.com/metbobnz/
Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom).
Weathergram archive (with translator) is at weathergram.blogspot.co.nz.
Contact is bob@metbob.com or text 64277762212.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
04 February 2024
Bob Blog 4 Feb
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.
Compiled Sunday 4 February 2024
A review of last month's weather
Here is a link to a YouTube clip giving an animated loop of the isobars and
streamlines in the South Pacific for the last month at youtu.be/BeFD1a7Hhu4
During late January an MJO started to move across northern Australia and
triggered TC KIRILLY which moved onto Queensland and turned into a wet
depression, In early February (late last week) KIRILLY rejuvenated back into
a cyclone thanks probably to the warm rainwater flooding out to gulf of
Carpentaria. It is now a rain depression crossing central Australia.
Sea Surface temperature anomalies from psl.noaa.gov/map/clim/sst.shtml
There is now a stretch of warner than normal sea from Queensland to the
dateline and to the east of NZ. This may well herald a cyclone path over
next few weeks.
Average isobars for past month (below)
As far as the monthly averaged weather map is concerned, there has NOT been
much change during February.
The Siberian HIGH has expanded and intensified. In the Southern Hemisphere,
the subtropical ridge has weakened SW of Australia and over NZ .
The South Tasman Sea turned into a low breeding area during February. Apart
from that there wasn't much change around the globe.
The 1010 isobar has shifted south across Australia and New Caledonia and
northwards onto Tasmania and southern NZ .
TROPICS
KIRILLY reformed in Gulf of Carpentaria and moved into inland Australia and
is now a wet monsoonal low. There is a tropical depression in the Coral Sea
and it may deepen and move onto New Caledonia mid-eek.
WEATHER ZONES
The South Pacific Convergence zone is strong and lingers on north side of a
stretched-out trough linking a well-formed LOW L1 in the Coral Sea with a
low lingering between Niue and Aitutaki L2 and another briefly near Tahiti
mid-week: L3. Brace for lightning in the squalls with these lows and the
SPCZ.
HIGHS and LOWS
A Thundery trough crossed NZ on Saturday, opening the door so that NZ may
get some hot air from Australia in a slow-moving High next few days.
There is forecast to be a weak southerly change along East Coast around
Thursday, and a more significant trough by Saturday then another HIGH for
early next week.
Panama to Marquesas:
7 to 11 Feb are the better days for departure from Panama in order to
capture a burst of NE winds out across the Panama Gulf.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about your voyage, then check metbob.com to
see what I offer.
Or Facebook at /www.facebook.com/metbobnz/
Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe
at bottom).
Weathergram archive (with translator) is at weathergram.blogspot.co.nz.
Contact is bob@metbob.com or text 64277762212.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world.
Compiled Sunday 4 February 2024
A review of last month's weather
Here is a link to a YouTube clip giving an animated loop of the isobars and
streamlines in the South Pacific for the last month at youtu.be/BeFD1a7Hhu4
During late January an MJO started to move across northern Australia and
triggered TC KIRILLY which moved onto Queensland and turned into a wet
depression, In early February (late last week) KIRILLY rejuvenated back into
a cyclone thanks probably to the warm rainwater flooding out to gulf of
Carpentaria. It is now a rain depression crossing central Australia.
Sea Surface temperature anomalies from psl.noaa.gov/map/clim/sst.shtml
There is now a stretch of warner than normal sea from Queensland to the
dateline and to the east of NZ. This may well herald a cyclone path over
next few weeks.
Average isobars for past month (below)
As far as the monthly averaged weather map is concerned, there has NOT been
much change during February.
The Siberian HIGH has expanded and intensified. In the Southern Hemisphere,
the subtropical ridge has weakened SW of Australia and over NZ .
The South Tasman Sea turned into a low breeding area during February. Apart
from that there wasn't much change around the globe.
The 1010 isobar has shifted south across Australia and New Caledonia and
northwards onto Tasmania and southern NZ .
TROPICS
KIRILLY reformed in Gulf of Carpentaria and moved into inland Australia and
is now a wet monsoonal low. There is a tropical depression in the Coral Sea
and it may deepen and move onto New Caledonia mid-eek.
WEATHER ZONES
The South Pacific Convergence zone is strong and lingers on north side of a
stretched-out trough linking a well-formed LOW L1 in the Coral Sea with a
low lingering between Niue and Aitutaki L2 and another briefly near Tahiti
mid-week: L3. Brace for lightning in the squalls with these lows and the
SPCZ.
HIGHS and LOWS
A Thundery trough crossed NZ on Saturday, opening the door so that NZ may
get some hot air from Australia in a slow-moving High next few days.
There is forecast to be a weak southerly change along East Coast around
Thursday, and a more significant trough by Saturday then another HIGH for
early next week.
Panama to Marquesas:
7 to 11 Feb are the better days for departure from Panama in order to
capture a burst of NE winds out across the Panama Gulf.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about your voyage, then check metbob.com to
see what I offer.
Or Facebook at /www.facebook.com/metbobnz/
Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe
at bottom).
Weathergram archive (with translator) is at weathergram.blogspot.co.nz.
Contact is bob@metbob.com or text 64277762212.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Subscribe to:
Posts (Atom)