006 axpz20 knhc 210351 twdep

Tropical weather discussion
NWS TPC/National Hurricane Center Miami FL
0405 UTC Sat Nov 21 2009
Tropical weather discussion for the eastern Pacific Ocean from 
the Equator to 32n...east of 140w. 
Based on 0000 UTC surface analysis and satellite imagery through 
0215 UTC.
...ITCZ...
the ITCZ axis extends from 05n76w to 04n83w to 06n89w to 08n120w 
to 07n140w. Scattered moderate to isolated strong convection 
within 240 nm N of axis and 90 nm S of axis W of 118w. 
...Discussion...
W of 115w...a deep layer trough extending from just inland along 
the coasts of Washington-Oregon-N cal to 34n121w continued to 
dig E-se on the east side of Rex block centered on the large 
ridge N of Hawaii. An associated cold front extends from central 
California to 30n128w to 28n40w and continues W to W-NW as a 
shear axis. The front was shifting E-se into central California 
and approaching NE portions of the forecast area. A 1020 mb high 
near 27n132w has collapsed...with the stronger central Pacific 
Ridge...centered on a 1027 mb surface high along 34n and N of 
Hawaii...was sliding and building ewd behind the cold front. 
Morning scatterometer passes showed moderate to fresh 20-25 kt 
trade winds S of the high pres from generally 20-22n to the nrn 
fringes of the ITCZ along 07.5n from 114w wwd beyond 140w. The 
resultant wind waves were mixing with a fading pulse of NW swell 
to produce seas of 8 to 11 ft N of 10n and W of 115w...with seas 
up 12 to 14 ft from 17n138w downwind...in the strongest NE trade 
wind flow. Farther E...the trade wind flow has diminished 
slightly from yesterday as the high to the north has collapsed. 
These fresh trades to the W will expand and spread farther E 
during the next 24-36 hours as the central Pacific high 
continues to build E behind the front N of the area. The front 
itself is expected to become diffuse by Sat night across NE 
portions of the area as the associated upper dynamics lift out. 
Meanwhile divergent flow aloft on the right rear entrance area 
of a weak jet Max on the se side of the upper trough is 
interacting with the modest trade wind convergence to enhance 
scattered convection N of the ITCZ W of 118w. Looking ahead the 
weekend...the blocking ridge N of Hawaii will break down ahead 
of an approaching central Pacific trough. This will allow the 
surface ridge that has begun to build behind the current 
weakening W coast cold front to remain in place N of the 
area...maintaining a broad swath of fresh to strong trades from 
10n to 25n W of 120w. Se cross-equatorial flow will converge 
with the NE trades to keep clusters of convection active along 
the ITCZ W of 120w as well. Meanwhile another pulse of NW swell 
yielding combined seas of 10 ft and greater will dominate most 
of the marine area W of 115w tonight through Sat. 
E of 115w...the main weather phenomena remains the persistent 
Central America gap winds. Morning high resolution scatterometer 
data showed nely winds of 20 to 25 kt through the Gulf of 
papagayo...enhanced by drainage effects... with 20 kt winds 
noted off of the Gulf of fonseca. Both of these area are 
expected to continue with 20 kt offshore gap winds...but are 
likely to diminish slightly during the daylight hours. Fresh 
trade winds were pushing from the SW Caribbean S across Panama 
as well...through the Gulf of Panama to the ITCZ off the 
Colombian coast...but are expected to diminish below 20 kt 
within 24 hours. Morning scatterometer data also showed nly flow 
of 20-25 kt persisting to flow S out through the Gulf of 
Tehuantepec...but is forecast to diminish briefly tonight before 
Post frontal winds across the W Gulf of Mexico flow begin to 
drain through the pass again late Saturday.
$$
Stripling







« Back to the Tropical Weather Page