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Tropical weather discussion
NWS TPC/National Hurricane Center Miami FL
1005 UTC sun Nov 08 2009


Tropical weather discussion for the eastern Pacific Ocean from
the Equator to 32n...east of 140w.


Based on 0600 UTC surface analysis and satellite imagery through
0730 UTC.


...Tropical lows...


The 1008 mb low pres system centered near 13n90w is slowly
moving N slowly in response to the upper trough immediately to
its W which has been contributing both southwesterly wind shear
and dry air...which is being entrained by the low...for over a
day. This persistent system is finally expected to dissipate to
a trough over the next 24 hours within this hostile environment.
In the meantime...scattered moderate with isolated strong
convection is displaced from the low level center and is found
mainly over land within 150 nm NE quadrant. The ascat pass from
0304 UTC showed southerly winds in the 20 to 25 kt range within
90 nm E semicircle of the low.


The 1009 mb low pres system centered near 11n118w has weakened
over the last 24 hours as the southwest to westerly upper jet to
its N has begun to sink southward...providing 20 to 30 kt of
shear over the system. Convection has once again increased
during the overnight hours with the system...but is displaced
between 120 nm and 240 nm E of the low center due to the shear
aloft. This low is also expected to dissipate to a trough later
today.


...ITCZ...


The ITCZ axis extends along 08n78w to 11n87w to 07n95w to
11n115w to 08n140w. Scattered moderate convection lies in the
Gulf of Panama within 45 nm either side of the ITCZ axis between
78w and 80w. Scattered moderate with isolated strong convection
can be found within 120 nm N of the ITCZ axis W of 137w.


...Discussion...


An upper low lies over West Texas and has a 50 to 70 kt westerly
upper jet extending from its southern edge along 22n to 122w
where it takes a southerly turn on the leading edge of an upper
trough to near 12n138w. The upper level diffluence associated
with the rear right quadrant of the jet is supporting scattered
moderate with isolated strong convection within 120 nm N of the
ITCZ axis W of 137w. Cirrus extending from this area of
convection can be found along the jet axis W of 125w. This jet
is inhibiting deep convection N of 15n where a broken
stratocumulus field can be found.


A high pres ridge stemming from a 1026 mb high near 33n136w
dominates north waters at the surface. This high pres system is
part of a larger North Pacific ridge that is currently being
compromised by a cold front well north of the forecast area.
While this front is expected to dissipate as it reaches forecast
waters Tue...long period NW swell from the system has already
pushed into N waters with significant wave heights to 18 ft.
This swell will spread se through the forecast area W of 105w
over the next few days...with maximum wave heights over N waters
subsiding to the 10 to 14 ft range Mon evening. The se
progression of the cold front N of forecast waters will weaken
the surface high pres ahead of it and force the high center se.
Easterly trade winds will persist through the forecast period on
the S side of the ridge axis and W of the aforementioned low
pres system near 11n118w. Quikscat passes from 0222 and 0404 UTC
show a broad area of NE winds in the 15 to 25 kt range here.


An upper anticyclone is over the SW Caribbean near 13n76w with a
ridge extending W to near 13n85w. The upper level flow is
diffluent over the Gulf of Panama between this ridge axis and a
northeasterly upper jet over Colombia...allowing for scattered
moderate convection in the Gulf of Panama within 45 nm either
side of the ITCZ axis between 78w and 80w. Little change is
expected in this pattern over the next few Days.


Gap winds...
the 0304 UTC ascat pass showed N winds in the 20 to 25 kt range
lingering in the Gulf of Tehuantepec. Winds are expected to
diminish below 20 kt this afternoon...but this should be a short
reprieve. North winds are expected to once again funnel through
The Isthmus of Tehuantepec overnight Mon night as a cold front
passes south through NE Mexico and the western Gulf of Mexico on
the western side of Hurricane Ida. It should be noted that there
is considerable uncertainty in the timing and strength of The
Gap winds in the Gulf of Tehuantepec due to the uncertainty in
the track and intensity of Ida. Interests in the vicinity of the
Gulf of Tehuantepec should monitor the High Seas Forecast the
next few days as many of the forecast models show winds
increasing again to gale strength by Tue.


$$
Schauer

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