000
AXPZ20 KNHC 311605
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT OCT 31 2009

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1545 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE WAS CENTERED ALONG 11N86W TO 
10N96W TO 9N110W TO 11N121W TO 8N131W TO 6N140W. SCATTERED STRONG
CONVECTION WAS WITHIN 120 NM S OF OF THE AXIS BETWEEN 123W-127W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION WAS WITHIN 120 NM 
S OF THE AXIS BETWEEN 131W-134W. SCATTERED MODERATE CONVECTION 
WAS WITHIN 120 NM S OF THE AXIS BETWEEN 109W-112W.

...DISCUSSION...

A DEEP LAYERED TROUGH HAS EXITED THE AREA...AND IS NOW OVER
NE MEXICO. IN ITS WAKE...MID/UPPER LEVEL RIDGING IS OVER THE 
EASTERN PORTION OF THE AREA E OF 121W WITH A MEAN RIDGE AXIS
EXTENDING FROM THE SW U.S. SW TO 21N116W TO AN UPPER LEVEL
ANTICYCLONIC CIRCULATION NEAR 10N118W. A JET STREAM BRANCH 
ENTERS THE REGION THROUGH 12N140W...AND EXTENDS NE TO 18N130W
TO 21N120W...THEN DIVES SE TO NEAR 18N108W. MAXIMUM JET CORE 
WINDS ARE IN THE RANGE OF 60-90 KT NEAR THE JET CORE. TO THE 
W OF THE MID/UPPER LEVEL RIDGE...A NEARLY STATIONARY MID/UPPER 
LEVEL CYCLONIC CIRCULATION IS NEAR 24N133W WITH A TROUGH SW TO
15N140W. TO THE W OF THE TROUGH...A VERY SHARP AND LARGE UPPER 
RIDGE WITH ITS CREST SPILLING SE INTO THE FAR NW PORTION OF
THE AREA.

MODERATE TO STRONG SUBSIDENCE WITH ASSOCIATED DRY AND 
STABLE AIR IS EVIDENT TO THE NW OF THE JET STREAM...EXCEPT
FOR A NARROW SWATH OF UPPER LEVEL MOISTURE SEEPING SSW BETWEEN
THE MID/UPPER LEVEL CYCLONIC CIRCULATION AND THE RIDGE SPILLING
INTO THE NW PORTION OF THE AREA. LATEST SATELLITE VISIBLE IMAGERY
SHOWED PATCHES OF BROKEN STRATOCUMULUS CLOUDS MOVING SW OVER 
THIS AREA. AT THE SURFACE...A NEARLY STATIONARY 1026 MB HIGH 
CENTER N OF THE AREA NEAR 34N134W EXTENDS A RIDGE SE TO NEAR 
23N119W. THE PRES DIFFERENCE BETWEEN THE HIGH AND LOWER PRES TO 
THE SE IS RESULTING IN NW-N WINDS OF 20-25 KT THROUGH THE GULF 
OF CALIFORNIA N OF 23N. THESE WINDS ARE EXPECTED TO DIMINISH TO 
LESS THAN 20 KT IN ABOUT 12 HOURS AS THE PARENT N OF THE AREA
BEGINS TO SHIFT NE AND WEAKEN. SLIGHTLY TIGHTER PRES GRADIENT ON 
THE SOUTHERN PERIPHERY OF THE RIDGE IS INDUCING AN AREA OF NE-E 
TRADES OF 20 KT FROM 15N-24N W OF 118W. THIS AREA WILL SHIFT
FROM 15N-22N W OF 130W IN 24 HOURS AND CHANGE LITTLE IN 48 
HOURS.

OVER THE EASTERN PORTION...AN UPPER LEVEL LOW OVER W GUATEMALA
IS MOVING W ABOUT 10 KT. TO ITS W BROAD ANTICYCLONIC FLOW 
ASSOCIATED WITH THE ANTICYCLONIC CIRCULATION NEAR 10N118W COVERS 
THE AREA S OF 20N E OF 122W. DIFFLUENCE ALOFT BETWEEN THE UPPER 
LEVEL LOW AND THE ANTICYCLONIC FLOW IS MAINTAINING ACTIVE 
CONVECTION ALONG AND NEAR THE ITCZ ACROSS THIS PORTION OF THE 
EPAC...AS THE MONSOONAL GYRE DOMINATES E OF 100W. GLOBAL MODELS 
CONTINUE TO SUGGEST THAT LOW PRES MAY FORM OVER THE AREA S OF 
GUATEMALA AND SE MEXICO. VISIBLE SATELLITE IMAGERY SHOWED A WEAK 
1008 MB LOW NEAR 11N96W DRIFTING W.

GAP WINDS...
STRONG HIGH PRES BUILDING SE ACROSS SOUTHERN MEXICO IN THE WAKE 
OF A COLD FRONT OVER THE WESTERN GULF OF MEXICO WILL USHER N-NE 
WINDS OF 20-25 KT THROUGH THE GULF OF TEHUANTEPEC BEGINNING LATE
LATE THIS AFTERNOON AND INTO SUN MORNING. THESE WINDS ARE 
FORECAST TO INCREASE TO GALE FORCE BY DAYBREAK SUN MORNING WITH 
SEAS BUILDING UP TO 15 FT. WINDS MAY PEAK UP TO 40 KT BEFORE 
DIMINISHING SLIGHT SUN MORNING BUT MAY BE PROLONGED IF STRONGER 
LOW PRES FORMS S OF THE GULF OF TEHUANTEPEC AS STATED ABOVE.

$$
AGUIRRE