000
AXPZ20 KNHC 212141
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC WED MAR 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 ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2115 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
ITCZ AXIS IS FROM 10N104W TO 06N115W TO 04N130W. SCATTERED 
SHOWERS WITHIN 75 NM EITHER SIDE OF AXIS E OF 121W. 


...DISCUSSION...

THE UPPER RIDGE ANCHORED NEAR 28N122W IS WEDGED BETWEEN A 
LONGWAVE UPPER TROUGH APPROACHING THE NW PORTION OF THE 
DISCUSSION AREA SUPPORTING A COLD FRONT JUST W OF 140W AND A 
SLOW MOVING UPPER TROUGH CURRENTLY SITUATED OVER THE CENTRAL 
PLAIN STATES AND MEXICO INTO THE FAR W GULF OF MEXICO. UPPER 
LEVEL WESTERLIES PREVAIL TO THE S OF THESE FEATURES...MAINLY S 
OF 13N E TO ACROSS CENTRAL AMERICA.   

THE BROAD SURFACE RIDGE AHEAD OF THE COLD FRONT HAS BEGUN TO 
WEAKEN EXTENDING FROM NEAR 28N133W SE TO NEAR 17N116W. THE 
SURFACE RIDGE OVER THE ROCKIES COUPLED WITH THE DEEP LAYERED 
TROUGH OVER THE CENTRAL PLAIN STATES IS PRODUCING NW WINDS OF 
20-25 KT THROUGH THE GULF OF CALIFORNIA AND ARE CONFINED TO 
MAINLY FROM 23N TO 29N. THESE WINDS ARE FORECAST TO DROP TO LESS 
THAN 20 KT BY 24 HRS.

S OF THE SURFACE RIDGE IS AN ELONGATED ZONE OF FRESH NELY 
TRADEWINDS FROM 06N TO 16N W OF 122W AND ALSO FROM 8N TO 15N 
BETWEEN 111W AND 122W. NE WIND WAVES ARE COMBINING WITH MODERATE 
TO LARGE NW SWELL ACROSS THE REGION TO PRODUCE SEAS OF 8 TO 10 
FT. 

THE COLD FRONT SUPPORTED BY THE APPROACHING LONGWAVE UPPER 
TROUGH WILL MOVE INTO THE FAR NW PORTION OF THE FORECAST AREA 
EARLY THIS EVENING ROUGHLY ALONG A LINE FROM 32N134W TO 28N140W. 
THE COLD FRONT IS FORECAST TO REACH FROM 30N128W TO 26N134W TO 
24N140W BY 24 HRS...THEN BEGIN TO DISSIPATE AS IT REACHES FROM 
30N124W TO 22N140W BY 48 HRS. A TIGHT PRES GRADIENT NW OF THE 
FRONT WILL BRING N WINDS OF 20-25 KT BEHIND IT...BUT WINDS 
GRADUALLY VEER AROUND TO THE NE AND DIMINISH TO 20 KT BY 48 HRS 
WITHIN 150 NM NW OF THE COLD FRONT.

E OF 100W IS A PERSISTENT SURFACE TROUGH EXTENDING FROM THE 
COAST OF COSTA RICA NEAR 10N85W TO 4N94W TO 2N100W. SCATTERED 
MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 250 NM SE OF THE 
TROUGH E OF 91W. THIS AREA OF CONVECTION IS EXPECTED TO REMAIN 
VERY ACTIVE THROUGH TONIGHT BEFORE WEAKENING. OTHERWISE...LIGHT 
TO MODERATE WINDS UNDER A WEAK PRES PATTERN WITH LOW SEA STATE 
OF 6 OF LESS PREVAIL GENERALLY TO THE E OF 105W.

ALSO WITH REGARDS TO MARINE ISSUES...VERY LONG PERIOD SRN 
HEMISPHERIC SWELLS ARE FORECAST TO MOVE INTO THIS AREA THU 
AFTERNOON AND ACT TO ELEVATE SEA HEIGHTS TO POSSIBLY AROUND 8 FT 
ALONG THE EQUATOR...WITH SOME POTENTIAL THAT THE ASSOCIATED WAVE 
ENERGY MAY LEAD TO HAZARDOUS SURF CONDITIONS AFFECTING THE 
CENTRAL AMERICAN COAST THU NIGHT THROUGH FRI. 

$$
PAW