000
AXPZ20 KNHC 180923
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED NOV 18 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 INTERTROPICAL CONVERGENCE ZONE IS CENTERED ALONG A LINE FROM 
08N78W TO 07N105W TO 06N107W TO 10N130W TO 11N137W. SCATTERED 
MODERATE AND ISOLATED STRONG CONVECTION CAN BE FOUND WITHIN 90 
NM S OF THE AXIS BETWEEN 79W AND 82W AND WITHIN 90 NM EITHER 
SIDE OF THE AXIS BETWEEN 123W AND 130W. NUMEROUS MODERATE AND 
SCATTERED STRONG CONVECTION CAN BE FOUND WITHIN 150 NM EITHER 
SIDE OF THE AXIS BETWEEN 130W AND 138W.

...DISCUSSION...
A SURFACE COLD FRONT IS MOVING THROUGH THE FAR NW PORTION OF THE 
AREA FROM 30N129W TO 26N140W AHEAD OF A DEEP MID TO UPPER LEVEL 
TROUGH EXTENDING N OF THE AREA FROM NEAR POINT CONCEPCION CA TO 
27.5N140W. A 0300 UTC QUIKSCAT PASS AND A 0624 UTC ASCAT PASS 
BOTH INDICATED N TO NE WINDS OF 20 TO 25 KT W OF THE FRONT. 
AHEAD OF THE FRONT A RIDGE EXTENDS FROM A SURFACE HIGH CENTERED 
NEAR 26N133W TO NEAR 16N112W. A TIGHT PRES GRADIENT REMAINS IN 
PLACE BETWEEN THE HIGH AND LOWER PRES TO THE S/THE ITCZ...WITH 
NE TO E TRADES IN THE 20 TO 25 KT RANGE PERSISTING W OF 120W. 
THE FRONT WILL WEAKEN AND DISSIPATE AS IT MOVES FARTHER TO THE 
SE TODAY AS THE RIDGE HOLDS IN PLACE. BUILDING NW SWELL UP TO 15 
FT WILL PROPAGATE THROUGH A LARGE 
PORTION OF THE AREA BEHIND THE FRONT...MAINLY N OF 09N AND W OF
114W...GRADUALLY DECAYING AS IT MOVES FARTHER TO THE S. ANOTHER 
COLD FRONT WILL APPROACH THE NW CORNER BY THU NIGHT REACHING 
FROM NEAR 30N130W TO 26N135W BY FRI...WITH YET ANOTHER SET OF NW 
SWELL OF UP TO 15 FT ARRIVING BEHIND IT FRI THROUGH THE WEEKEND. 

CONVECTION IS BEHIND ENHANCED ALONG THE ITCZ W OF 120W MAINLY 
DUE TO TRADE WIND CONVERGENCE AND DIVERGENT FLOW ALOFT ON THE SE 
SIDE OF A MID TO UPPER LEVEL TROUGH EXTENDING FROM THE S BAJA 
PENINSULA ALL THE WAY TO JUST SE OF THE BIG ISLAND OF HAWAII. A 
PAIR OF SURFACE TROUGHS ARE EMBEDDED IN THE ITCZ EXTENDING FROM 
13N130W TO 08N132.5W AND FROM 18N136W TO 08N139W RESPECTIVELY... 
AS CAPTURED BY A 0304 UTC QUIKSCAT PASS AND A 0620 UTC ASCAT 
PASS. ANOTHER SURFACE TROUGH LOCATED NEAR 10N106W TO 05N107W IS 
WEAKENING AS IT ENCOUNTERS DEEP SW SHEAR ALOFT AND DRY AIR JUST 
TO THE W OF THE TROUGH AXIS AS INDICATED BY UPPER LEVEL 
SATELLITE WIND DATA AND WATER VAPOR SATELLITE IMAGERY. 

GAP WINDS...
A GALE WARNING CONTINUES IN THE GULF OF TEHUANTEPEC AND ADJACENT 
AREA. WINDS WILL DIMINISH TO LESS THAN GALE FORCE BY THIS 
AFTERNOON AS THE COLD FRONT THAT MOVED THROUGH THE S GULF OF 
MEXICO YESTERDAY WEAKENS AND RESULTANT NORTHERLY FLOW ACROSS THE 
ISTHMUS OF TEHUANTEPEC EASES. NE TO E WINDS IN THE 20 TO 25 KT 
RANGE WILL PERSIST ACROSS THIS SAME AREA THROUGH THU THEN WILL 
DIMINISH TO LESS THAN 20 KT BY THU NIGHT AS HIGH PRES BUILDS 
OVER THE S GULF OF MEXICO. 

TO THE SOUTHEAST...GRADIENT FLOW ALONG WITH DRAINAGE EFFECTS WILL
ALLOW FOR 20 TO 25 KT NE TO E WINDS THROUGH THE GULF OF PAPAGAYO 
THROUGH FRIDAY. 

$$
LEWITSKY