000
AXPZ20 KNHC 031554
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC THU DEC 03 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 
1500 UTC.

...ITCZ...
THE ITCZ AXIS IS ALONG AXIS IS ALONG 05N77W TO 10N20W TO 07N130W 
TO 08N135W TO 07N140W. SCATTERED MODERATE TO ISOLATED STRONG 
CONVECTION WITHIN 120 NM N OF AXIS AND 60 NM S OF AXIS BETWEEN 
120W AND 128W. SCATTERED MODERATE CONVECTION WITHIN 60 NM EITHER 
SIDE OF AXIS BETWEEN 130W AND 135W.

...DISCUSSION...
AN UPPER RIDGE ALONG 120W WILL SHIFT E AND WEAKEN AHEAD OF A 
SHORT WAVE TROUGH ALONG 145W N OF 20N THAT WILL TRACK 
E...REACHING THE BAJA COAST SAT. THIS WILL SUPPRESS A 1017 MB 
SURFACE RIDGE CENTERED NEAR 29N130W. THE PRESSURE GRADIENT SOUTH 
OF THE SURFACE RIDGE REMAINS SOMEWHAT TIGHT NONETHELESS...DUE IN 
PART TO PERSISTING AREAS OF 1007 MB SURFACE LOW PRES ALONG THE 
ITCZ...NAMELY NEAR 120W AND 135W. STRONG CONVECTION CONTINUES 
ALONG THE ITCZ NEAR THESE AREAS...ALTHOUGH SLIGHTLY DIMINISHED 
FROM YESTERDAY. ASCAT DATA ALONG WITH TOGA TAO BUOYS SHOWED 15 
TO 20 KT SOUTHERLY FLOW CONVERGING WITH THE FRESH TRADES N OF 
THE ITCZ.  THIS CONVERGENCE HAS BEEN A TRIGGER FOR THE STRONG 
ITCZ CONVECTION IN CONJUNCTION WITH PRE-EXISTING UPPER DIVERGENT 
FLOW ASSOCIATED AN UPPER ANTICYCLONE OVER THE ITCZ W OF 120W. 
THE INTENSITY OF THE CONVECTION MAY ALSO BE DUE IN PART TO THE 
MID AND UPPER LEVELS OF THE ATMOSPHERE BEING SLIGHTLY MORE 
UNSTABLE THAN USUAL...AS EVIDENCED BY GOES SOUNDER DATA IN THE 
AREA. ASCAT DATA ALSO HINTED OF A 1007 MB SURFACE LOW NEAR 
16N135W. THIS FEATURE IS TIED TO THE SHORT WAVE TROUGH TO ITS NW 
AND IS EXPECTED TO WEAKEN AS THE TROUGH LIFTS OUT. 

LONG PERIOD NW SWELL CONTINUES ACROSS MOST OF THE AREA W OF 
110W...MIXING WITH NE SWELL IN THE AREA OF TRADES.

NORTHERLY FLOW IS EXPECTED TO INCREASE TO 20-25 KT OVER THE GULF 
OF CALIFORNIA N OF 27N LATE TODAY AND TONIGHT AS HIGH PRES 
BUILDS OVER THE GREAT BASIN.

GAP WINDS...
EXPECT ELY WINDS AT OR NEAR 20 KT TO PULSE UP AND DOWN THROUGH 
THE GULF OF PAPAGAYO AND THEN DOWNSTREAM TO NEAR 89W DURING THE 
NEXT FEW DAYS. THESE WINDS WILL BE STRONGEST IN THE MORNING 
HOURS WITH THE AID OF DRAINAGE FLOW. ALSO...A GALE FORCE WIND 
EVENT IS EXPECTED TO DEVELOP ACROSS THE GULF OF TEHUANTEPEC IN 
ABOUT 60 HOURS...SAT AFTERNOON...AS A STRONG HIGH PRES BUILDS 
SWD INTO THE FAR WRN GULF OF MEXICO AND ALONG THE EASTERN SLOPES 
OF THE SIERRA MADRE MOUNTAINS OF MEXICO IN THE WAKE OF A STRONG 
COLD FRONT FORECAST TO MOVE ACROSS THE ENTIRE GULF REGION ON SAT.

OF NOTE...THE MONTHLY DISTRIBUTION OF TEHUANTEPEC EVENTS SHOWS 
THAT THE LARGEST NUMBER OF GALE FORCE EVENTS OCCURS IN DECEMBER. 
STORM-FORCE EVENTS OCCUR MOST OFTEN IN JANUARY. GALE FORCE 
EVENTS HAVE OCCURRED AS EARLY AS SEPTEMBER AND AS LATE AS MAY. 
HOWEVER...ABOUT 84% OF ALL EVENTS TAKE PLACE BETWEEN NOVEMBER 
AND MARCH. 

$$
GR/CHRISTENSEN