000
AXPZ20 KNHC 051534
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SUN APR 05 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 
1530 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE LIES ALONG A LINE FROM 05N77W 
TO 07N85W TO 02N115W TO 04N140W. ISOLATED MODERATE WITHIN 90 NM 
OF AXIS BETWEEN 88W AND 98W.

...DISCUSSION...
A LATE SEASON GULF OF TEHAUNTEPEC STORM FORCE WIND EVENT WILL BE 
INDUCED BY A COLD FRONT PASSING THROUGH THE BAY OF CAMPECHE 
MONDAY...SENDING STRONG NORTHERLY FLOW THROUGH THE ISTHMUS OF 
TEHUANTEPEC BEGINNING LATE MON AFTERNOON. THE FRONT IS EXPECTED 
TO BE PARTICULARLY POTENT FOR THIS TIME OF THE YEAR...ALLOWING 
MID LEVEL ENERGY TO PASS SOUTHWARD FROM THE SUPPORTING DEEP 
LAYER TROUGH OVER THE GULF OF MEXICO THROUGH SOUTHERN MEXICO 
INTO THE PACIFIC ON THE EASTERN EDGE OF A STRONG MID TO UPPER 
LEVEL ANTICYCLONE. WINDS IN THE GULF OF TEHUANTEPEC WILL QUICKLY 
INCREASE TO STORM FORCE TUE MORNING. IN ADDITION...THE PRESSURE 
GRADIENT BETWEEN LARGE HIGH PRESSURE OVER THE GREAT 
BASIN/SOUTHERN PLAINS OF THE U.S. AND LOWER PRESSURES OVER NW 
MEXICO WILL INDUCE WINDS TO 20 KT OVER THE GULF OF CALIFORNIA 
LATER TODAY. WINDS MAY INCREASE FURTHER TO 20 TO LOCALLY 30 KT 
EARLY MON...BEFORE ENDING MON NIGHT.

A COLD FRONT HAS ENTERED THE FAR NW WATERS AND EXTENDS FROM 
30N135W TO 27N140W. NW SWELL ASSOCIATED WITH THE FRONT IS 
LAGGING BEHIND...HOWEVER SEAS SHOULD BUILD TO THE 10 TO 15 FT 
RANGE BY THIS EVENING. THE DEEP LAYER TROUGH SUPPORTING THIS 
COLD FRONT IS IN THE PROCESS OF CUTTING OFF FROM THE NORTHERN 
STREAM FLOW WITH A COMPLEX UPPER LOW DEVELOPING NEAR 38N135W. 
THIS UPPER LOW IS FORECAST TO DIVE SOUTHEAST THROUGH MON...THEN
SLOWLY LIFT EAST-NORTHEASTWARD TOWARD CALIFORNIA ON TUE. THE 
ASSOCIATED COLD FRONT WILL BE SLOW TO MOVE EASTWARD AS A 
RESULT...ALLOWING THE NW SWELL TO MOVE AHEAD OF THE SURFACE 
BOUNDARY BEGINNING MON. NO CONVECTION IS ASSOCIATED WITH THIS 
COLD FRONT AS IT LIES WITHIN A VERY DRY AIR MASS GENERALLY N OF 
20N W OF 120W. 

AXIS OF THE SUBTROPICAL JET STREAM ORIGINATES SW OF HAWAII AND 
STRETCHES ALONG A LINE FROM 18N140W TO 23N125W TO CENTRAL BAJA 
CALIFORNIA. CORE SPEEDS WERE CLOSE TO 100 KT. THIS JET IS 
ADVECTING MID TO UPPER LEVEL MOISTURE EASTWARD ACROSS THE 
FORECAST AREA...WITH MULTILAYERED CLOUDINESS FOUND WITHIN 300 NM 
SOUTH OF THE JET AXIS NOTED ABOVE.

A WEAK UPPER TROUGH LIES S OF 10N ALONG 112W. VERTICAL LIFT 
ASSOCIATED WITH THE REAR RIGHT QUADRANT OF THE WEAK SOUTHERLY 
UPPER JET ON THE EASTERN EDGE OF THIS TROUGH IS ACTING ON 
PLENTIFUL LOW LEVEL MOISTURE...WITH PRECIPITABLE WATER VALUES IN 
EXCESS OF 2 INCHES. WHILE MUCH OF THIS REGION IS DOMINATED BY 
STRONG SUBSIDENCE ALOFT ASSOCIATED WITH THE ANTICYCLONE CENTERED 
NEAR 10N100W ...ISOLATED MODERATE CONVECTION WAS ABLE TO FORM IN 
THIS REGION WITHIN 90 NM OF THE ITCZ AXIS BETWEEN 88W AND 98W. 
ELSEWHERE EAST OF THIS UPPER TROUGH...THE STRONG ANTICYCLONE AND 
AN ASSOCIATED DRY AIR MASS ALLOWS SUBSIDENCE TO DOMINATE THE 
AREA S OF 20N. THIS RIDGE ENVELOPS SE MEXICO AND MOST OF CENTRAL 
AMERICA WHERE MOSTLY FAIR WEATHER PREVAILS.

$$
COBB