000
AXPZ20 KNHC 141619
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC WED DEC 14 2011

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH CROSSES CENTRAL AMERICA AND ENTERS EPAC NEAR 
09.5N84.5W TO 06N92W TO 05N108W THEN TRANSITIONS TO ITCZ TO 
09N128W TO 08N140W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION NOTED WITHIN 150 NM OF TROUGH E OF 96W. SCATTERED TO 
NUMEROUS MODERATE SCATTERED STRONG CONVECTION NOTED WITHIN 210 
NM N OF AXIS W OF 132W.

...DISCUSSION...
DOWN STREAM HIGH AMPLITUDE UPPER LEVEL PATTERN FROM CENTRAL U.S. 
ACROSS MOST OF ATLANTIC CONTINUES TO INDUCE MEAN MIDDLE TO UPPER 
LEVEL TROFFING ACROSS W AND SW U.S. AND EXTENDING S AND SW INTO 
THE DISCUSSION AREA. A DEEP-LAYER LONG WAVE TROUGH ACROSS 
WESTERN U.S. FROM ERN MONTANA TO A MID TO UPPER LEVEL CYCLONE 
OVER THE CA-NV-AZ BORDER IS SHIFTING E AND SE AS A 120 KT JET 
MAX HAS ROUNDED THE BASE OF TROUGH ACROSS NW MEXICO AND IS 
STREAKING NE TOWARDS THE CENTRAL U.S. BROAD TROUGH AXIS EXTENDS 
FROM THIS CYCLONE SW TO NEAR 23N124W...WITH UPPER LEVEL 
WESTERLIES DOMINATING THE AREA...GENERALLY N OF 17N AND E OF 
110W. REINFORCING SHORTWAVE ENERGY WILL DROP S INTO THIS MEAN 
TROUGH BY FRI TO REINVIGORATE THE DEEP LAYERED CYCLONE AND 
SUPPORT A COLD FRONT SINKING INTO NE PORTIONS. 

A DIFFUSE FRONTAL TROUGH HAS STALLED ACROSS SRN BAJA CALIFORNIA 
ALONG ABOUT 25N...WITH VERY DRY STABLE AIR TO THE N. STRONG NW 
WINDS TO THE NW OF THIS AREA 24 HOURS AGO HAVE DIMINISHED 
CONSIDERABLY OVERNIGHT. HOWEVER...N SWELL GENERATED FROM A LONG 
FETCH OF 20-30 KT WIND YESTERDAY W OF CALIFORNIA CONTINUES TO 
PROPAGATE SE AND MOVE INTO DISCUSSION AREA....WHERE SEAS OF 8 TO 
11 FT ARE FOUND N OF 20N AND E OF 135W IN THIS N TO NW SWELL.

EPAC HIGH PRES RIDGE EXTENDS FROM 1028 MB HIGH NEAR 31N142W SE 
TO THE DISSIPATING FRONTAL TROUGH...AND HAS INDUCED A TIGHT PRES 
GRADIENT BETWEEN RIDGE AND LOWER PRES ASSOCIATED WITH ITCZ 
DIRECTLY TO THE S OF THE HIGH. THIS IS SUPPORTING FRESH NE TRADE 
WINDS W OF 120W. STRONG LOW LEVEL CONVERGENCE BETWEEN THE ITCZ 
AND 12N FROM 130W TO 150W IS PRODUCING A LARGE AREA OF SCATTERED 
TO LOCALLY NUMEROUS CONVECTION DESCRIBED ABOVE...BEING FURTHER 
ENHANCED BY DIFFLUENT FLOW ALOFT. AN OVERNIGHT INCREASE IN 
SPATIAL COVERAGE AND VERTICAL GROWTH OF THIS CONVECTION HAS 
INDUCED FURTHER DIVERGENCE IN THE UPPER LEVEL FLOW FROM 08N TO 
12N BETWEEN 140W AND 150W. LITTLE CHANGE IS EXPECTED IN THE 
OVERALL WIND AND SEA STATE W OF 120W DURING THE NEXT 48 HOURS. 
LIKEWISE...CONVECTION CAN BE EXPECTED TO REMAIN VERY ACTIVE.

THE EDGE OF A 0352 UTC ASCAT PASS INDICATED PEAK WINDS 25-30 KT 
IN THE GULF OF TEHUANTEPEC. PRES GRADIENT ACROSS THE CHIVELA 
PASS HAS WEAKENED AND WINDS IN THE SW GULF ARE VEERING SOUTHWARD 
SO EXPECT WINDS GREATER THAN 20 KT TO CONTINUE THROUGH THIS 
AFTERNOON BEFORE DROPPING TO LESS THAN 20 KT TONIGHT.

MODEL GUIDANCE SHOWS SURFACE TROUGH INTENSIFYING OVER N-CENTRAL 
MEXICO DURING THE NEXT 2 DAYS...ALLOWING NW WINDS TO INCREASE TO 
20-25 KT IN THE GULF OF CALIFORNIA WED NIGHT THROUGH THU.

$$
STRIPLING