000
AXPZ20 KNHC 210901
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT APR 21 2012

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH IS FROM 09N84W TO 07N105W. ITCZ IS FROM 05N107W 
TO 05N115W AND FROM 07N122W TO 05N130W. SCATTERED MODERATE 
ISOLATED STRONG CONVECTION NOTED FROM 03N TO 06N BETWEEN 82W AND 
89W. SCATTERED MODERATE CONVECTION FROM 09N TO 11N BETWEEN 100W 
AND 105W. SCATTERED MODERATE ISOLATED STRONG CONVECTION FROM 08N 
TO 11N BETWEEN 115W AND 120W.  

...DISCUSSION...
THE MAIN ISSUE FOR THE NEXT 48 HOURS WILL BE THE ONSET OF GALE 
FORCE WINDS THROUGH THE GULF OF TEHUANTEPEC...DUE TO A 
UNSEASONABLY STRONG COLD FRONT PUSHING THROUGH THE GULF OF 
MEXICO. HIGH PRES WILL BUILD OVER THE SOUTHERN PLAINS AND NW 
GULF AS DEEPENING LOW PRES PUSHES THROUGH THE LOWER MISSISSIPPI 
VALLEY. THE TRAILING FRONT WILL MOVE THROUGH THE SW GULF LATER 
TODAY...FOLLOWED BY GAP WIND FLOW REACHING GALE FORCE BY LATE 
TONIGHT INTO THE GULF OF TEHUANTEPEC. THESE WINDS MAY DIMINISH 
SLIGHTLY BELOW GALE FORCE LATER ON SUN...BUT INCREASE AGAIN IN 
EXCESS OF GALE FORCE SUN NIGHT DUE TO NOCTURNAL DRAINAGE 
INFLUENCES. THE STRONG GAP FLOW WILL PERSIST THROUGH 
MON...CREATING A LONG PLUME OF NE TO E WINDS WITH FRESH NE SWELL 
WITH HEIGHTS OF 8 TO 11 FT REACHING AS FAR AS 800 NM SW OF THE 
GULF OF TEHUANTEPEC. 

ELSEWHERE S OF 20N...WEAK HIGH PRES N OF 20N WILL MAINTAIN 
GENERALLY LIGHT TO MODERATE TRADE WIND FLOW FROM ROUGHLY 06N TO 
20N W OF 110W THROUGH EARLY NEXT WEEK. SCATTERED CONVECTION 
PERSISTS ALONG A SURFACE TROUGH FROM 09N118W TO 05N121W. A LINE 
OF WEAKENING CONVECTION IS NOTED ALONG 10N BETWEEN 98W AND 105W. 
A WINDSAT PASS FROM 0022 UTC AND AN ASCAT PASS FROM 0424 UTC 
SHOW A VERY SHARP EXTENSION OF THE SURFACE RIDGE JUST TO THE 
NORTH OF THE CONVECTION...WITH WEAK E-W TROUGHING TO THE 
SOUTH...ALLOW JUST ENOUGH LOW LEVEL CONVERGENCE TO LIFT THE 
BOUNDARY LAYER MOISTURE TO INITIATE CONVECTION. SIMILARLY A 
HEALTHIER LINE OF THUNDERSTORMS IS NOTED ALONG 05N BETWEEN 82W 
AND 89W WHERE VERY LIGHT SW AND N WINDS ARE CONVERGING.

N OF 20N...A SHARP UPPER TROUGH N OF 23N ALONG 145W WILL MAKE 
MODEST PROGRESS EASTWARD DUE TO A BLOCKING UPPER RIDGE CENTERED 
OVER SOUTHERN CALIFORNIA. AN ASSOCIATED COLD FRONT IS 
APPROACHING THE AREA FROM THE N CENTRAL PACIFIC...BUT WILL MOVE 
VERY SLOWLY EASTWARD AS IT PUSHES INTO A 1023 MB SURFACE HIGH 
NEAR 32N135W ASSOCIATED WITH THE MID/UPPER RIDGE OVER SOUTHERN 
CALIFORNIA. SURFACE RIDGING EXTENDS TO THE SE TOWARD THE COAST 
OF MEXICO NEAR 20N110W. A SHIP REPORTED 20 KT N WINDS AT EDGE OF 
THE RIDGE OFF CABO CORRIENTES AT 0600 UTC. THE HIGH PRES WILL 
WEAKEN AND GRADUALLY DISSIPATE AHEAD OF THE ADVANCING DEEP LAYER 
TROUGH...BUT NOT BEFORE HIGH PRES BUILDS FURTHER SOUTH NEAR 
25N118W ABOUT 400 NM W OF CENTRAL BAJA...WHICH WILL ALSO SERVE 
TO IMPEDE THE EASTWARD ADVANCE OF THE COLD FRONT. THE FRONT WILL 
REACH FROM 35N130W TO 20N150W BY LATE SUN...THEN WILL START TO 
STALL AND WEAKEN FROM 35N127W TO 19N135W BY LATE MON. THE SLOWLY 
BUILDING HIGH PRES WILL ALSO ALLOW WINDS TO REMAIN FAIRLY LIGHT 
N OF 20N INTO EARLY NEXT WEEK. GLOBAL MODEL CONSENSUS SHOWS 
FRESH TO STRONG NW FLOW WILL FOLLOW THE COLD FRONT OVER THE FAR 
NW PORTION OF THE DISCUSSION AREA BY LATE MON...ACCOMPANIED BY 
NW SWELL WITH HEIGHTS OF 8 TO 12 FT.

$$
CHRISTENSEN