000
AXPZ20 KNHC 030917
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU DEC 03 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 
0900 UTC.

...ITCZ...
THE ITCZ AXIS IS ALONG AXIS IS ALONG 07N77W TO 08N99W TO 09N117W 
TO 08N130W TO 07N140W. SCATTERED MODERATE TO ISOLATED STRONG 
CONVECTION IS NOTED FROM 06N TO 11N BETWEEN 115W AND 130W. 
SIMILAR CONVECTION IS FROM 14N TO 20N BETWEEN 134W AND 138W. 
SCATTERED MODERATE CONVECTION IS FROM 06N TO 10N BETWEEN 130W 
AND 135W.

...DISCUSSION...
SURFACE HIGH PRESSURE...ANALYZED 1017 MB NEAR 27N131W... 
CONTINUES TO WEAKEN. AS A RESULT...THE AREA COVERAGE OF THE 
TRADE WINDS HAS ALSO DIMINISHED. HOWEVER...TIGHT PRES GRADIENT 
BETWEEN THE HIGH AND A LOW PRES NEAR 18N140W IS GENERATING AN 
AREA OF E TO SE WINDS 20 TO 25 KT MAINLY FROM 14N TO 21N W OF 
130W. AN ASCAT PASS FROM AROUND 0600 UTC SHOWS A FEW WIND BARBS 
OF 30 KT PROBABLY ASSOCIATED WITH THE CONVECTION AHEAD OF THE 
LOW PRES THAT COVERS THE AREA FROM 14N TO 20N BETWEEN 134W AND 
138W. ANOTHER SHORTWAVE TROUGH...CURRENTLY W OF THE AREA ALONG 
142W IS EXPECTED TO PASS ACROSS THE N PORTION OF THE FORECAST 
REGION...N OF 21N...THU NIGHT THROUGH SAT. THIS WILL FURTHER 
WEAKEN THE SURFACE HIGH PRESSURE AND DECREASE THE COVERAGE OF 
FRESH TRADES. 

A 1009 MB LOW PRES IS ALONG THE ITCZ NEAR 09N119W. A CLUSTER OF 
MODERATE TO ISOLATED STRONG CONVECTION IS WITHIN 60 NM W OF LOW 
CENTER. N TO NE WINDS OF 20 KT IS NOTED WITHIN 180 NM NW 
QUADRANT OF LOW CENTER. THIS SYSTEM IS EXPECTED TO MOVE MAINLY 
WWD AT ABOUT 10 KT DURING THE NEXT 24 HOURS. A DIFFLUENT PATTERN 
ALOFT IN HELPING TO INDUCE THE CONVECTIVE ACTIVITY AROUND THIS 
LOW PRES. 

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 THU 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