000
AXPZ20 KNHC 060331
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC MON APR 06 2009

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0330 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE LIES ALONG A LINE FROM 06N77W 
TO 02N100W TO 01N120W TO 04N140W. SCATTERED MODERATE CONVECTION 
IS WITHIN 100 NM S OF AXIS BETWEEN 90W AND 94W.

...DISCUSSION...
A LATE SEASON GULF OF TEHAUNTEPEC STORM FORCE WIND EVENT WILL BE 
INDUCED BY A STRONG COLD FRONT MOVING RAPIDLY SE ACROSS THE GULF 
OF MEXICO. THE FRONT IS EXPECTED TO PASS THROUGH THE BAY OF 
CAMPECHE ON MONDAY...SENDING STRONG NORTHERLY FLOW THROUGH THE 
ISTHMUS OF TEHUANTEPEC BEGINNING AROUND 07/0000 UTC. WINDS IN 
THE GULF OF TEHUANTEPEC WILL QUICKLY INCREASE TO STORM FORCE TUE 
MORNING. AT THIS TIME...THE GFS 925 MB WINDS SHOWS A PAIR OF 
WIND BARBS OF 50-55 KT. 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 BRIEFLY 
INDUCE WINDS TO 20 KT OVER THE GULF OF CALIFORNIA DURING THE 
NEXT 12 TO 24 HOURS. NE WINDS ARE ALSO EXPECTED TO INCREASE TO 
20 TO 25 KT OVER THE PACIFIC COASTAL WATERS OF COSTA RICA EARLY 
WED AS THE STRONG COLD FRONT CURRENTLY OVER THE NW PORTION OF 
THE GULF OF MEXICO MOVES ACROSS THE WESTERN CARIBBEAN.

A COLD FRONT IS PRESENTLY MOVING ACROSS THE NW WATERS. AT 
06/0000 UTC...THE FRONT ENTERS THE AREA NEAR 30N130W THEN 
CONTINUES SW TO NEAR 25N140W. LONG PERIOD NW SWELL IS LAGGING 
BEHIND THE FRONT...HOWEVER SEAS SHOULD BUILD TO THE 10 TO 15 FT 
RANGE OVER THE NW WATERS DURING THE OVERNIGHT HOURS. A COMPLEX 
UPPER LOW DEVELOPING NEAR 37N132W SUPPORTS THIS FRONT. THE  
UPPER LOW IS FORECAST TO DIVE SOUTHEAST THROUGH MON...THEN 
SLOWLY LIFT EAST-NORTHEASTWARD TOWARD CALIFORNIA LATE 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. 

THE AXIS OF THE SUBTROPICAL JET STREAM ORIGINATES SW OF HAWAII 
AND STRETCHES ALONG A LINE FROM 18N140W TO 22N125W TO CENTRAL 
BAJA CALIFORNIA. CORE SPEEDS ARE CLOSE TO 100 KT BUT WINDS 
INCREASE TO 110-130 KT OVER TEXAS. THIS JET IS ADVECTING MID TO 
UPPER LEVEL MOISTURE EASTWARD ACROSS THE FORECAST AREA...WITH 
MULTILAYERED CLOUDINESS FOUND WITHIN 400 NM SOUTH OF THE ABOVE 
MENTIONED JET AXIS.

AN INVERTED UPPER TROUGH EXTENDS FROM 09N119W TO A WEAK LOW 
LOCATED NEAR 01N116W. EAST OF THIS TROUGH AND SOUTH OF 
20N...MUCH OF THIS REGION IS DOMINATED BY STRONG SUBSIDENCE 
ALOFT ASSOCIATED WITH AN ANTICYCLONE CENTERED NEAR 14N99W. THIS 
FEATURE AND THE ASSOCIATED DRY AIR MASS ALSO COVERS SE MEXICO 
AND MOST OF CENTRAL AMERICA WHERE MOSTLY FAIR WEATHER PREVAILS.

OF NOTE...CLIMATOLOGICALLY THE TEHUANTEPEC WIND EVENTS OCCUR 
BETWEEN OCTOBER AND APRIL. ON AVERAGE...THE LAST EVENT TAKES 
PLACE AROUND APRIL FIRST. THE LATEST TEHUANTEPEC STORM EVENT ON 
RECORD OCCURRED APRIL 14-16 OF 2008 WITH A TOTAL DURATION OF 60 
HOURS.  

$$
GR