000
AXPZ20 KNHC 030958
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT DEC 03 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0830 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... 

MONSOON TROUGH AXIS CROSSES CENTRAL AMERICA AND ENTERS EPAC NEAR 
09N84W TO 06N95W TO LOW PRES NEAR 07N100W. ITCZ BEGINS FROM LOW 
TO 06N109W TO 10N116W TO 10N124W TO 08N140W. ISOLATED MODERATE 
TO STRONG CONVECTION NOTED WITHIN 60 NM OF AXIS W OF 122W.

...DISCUSSION...

A SHARP UPPER TROUGH EXTENDS FROM THE GREAT BASIN AND INTO THE 
SW U.S. REINFORCING SHORTWAVE ENERGY HAS DROPPED INTO THE BACK 
SIDE OF THE TROUGH DURING THE PAST 12-18 HOURS...CARVING OUT A 
BROAD TROUGH BASE...FROM THE SRN CALIFORNIA-ARIZONA BORDER SW  
ACROSS NRN BAJA CALIFORNIA TO NEAR 20N120W. PREVIOUS SHORT WAVE 
ENERGY HAS ROUNDED THE BASE OF THROUGH AND LIFTED OUT TO THE NE 
ACROSS COLORADO/CENTRAL ROCKIES...ALLOWING THE UPPER TROUGH TO 
STALL IN PLACE OVER THE SW CONUS. AN ASSOCIATED STATIONARY FRONT 
HAS BECOME ILL DEFINED OVER THE HIGH TERRAIN OF NWRN MEXICO 
EXTENDING SW ACROSS SRN BAJA CALIFORNIA. THE LIGHTNING DETECTION 
NETWORK CONTINUES TO SHOW STRIKES OCCURRING ALONG AND JUST AHEAD 
OF THE OLD FRONTAL BOUNDARY ALONG THE WRN SLOPES OF THE SIERRA 
MADRES. BROAD UPPER LEVEL RIDGES ARE FOUND BOTH TO THE SW AND SE 
OF THE UPPER TROUGH...EXTENDING FROM THE TROPICS N TO BEYOND 30N.

RECENT SURFACE OBSERVATIONS FROM ALONG BOTH COASTS OF THE GULF 
OF CALIFORNIA INDICATE LIGHT WINDS ACROSS THE GULF...AN 
INDICATION OF HOW MUCH THE FRESH NW FLOW BEHIND THE FRONT HAS 
DIMINISHED. HIGH PRES IS FORECAST TO BUILD ACROSS THE GULF 
REGION FROM THE N TONIGHT THROUGH EARLY NEXT WEEK AND WILL BEGIN 
TO PRODUCE FRESH TO STRONG NLY WINDS BY SUNDAY AFTERNOON...THEN 
STRENGTHEN MONDAY AFTERNOON AND NIGHT...POSSIBLY TO NEAR 30 KT.

HIGH PRES WELL N OF THE AREA ACROSS THE NE PACIFIC EXTENDS S 
ACROSS W PORTIONS OF THE DISCUSSION AREA...AND IS MAINTAINING 
FRESH NELY WINDS GENERALLY W OF 130W SOUTHWARD TO THE ITCZ ALONG 
ABOUT 08N. THIS WAS CONFORMED BY RECENT ASCAT PASSES AROUND 06 
UTC AND A FEW SHIP OBSERVATIONS. SEAS OF 8 TO 12 FT PREVAIL 
ACROSS THIS AREA IN A MIX OF N AND NEW NW SWELL AND BUILDING NE 
WIND WAVES. THIS WIND FLOW WILL DIMINISH AND VEER MORE NE TO E 
THROUGH 48 HOURS AS HIGH PRES N OF THE AREA WEAKENS SLIGHTLY AND 
DRIFTS SE. THIS WILL ALSO MAINTAIN FRESH NE TRADES BETWEEN 12N 
TO 20N W OF 125W. 

TO THE SE...A 1010 MB LOW PRES CENTER CONTINUED ALONG THE W END 
OF THE MONSOON TROUGH NEAR 07N100W AND WAS MOVING W AT 10-12 KT. 
A 0420 UTC ASCAT PASS SHOWED 20 TO 25 KT WINDS WITHIN 150 NM 
ACROSS THE NRN SEMICIRCLE OF THE LOW PRES. GLOBAL MODELS SUGGEST 
SOME INCREASE IN SOUTHERLY FLOW INTO THE LOW THROUGH 24 
HOURS...WITH THE LOW PERSISTING AT LEAST THROUGH 72 HOURS AS IT 
SHIFTS WNW AROUND 10 KT. THIS IS PLAUSIBLE THROUGH 48 HOURS 
GIVEN THAT THE LOW WILL MOVE INTO INTO THE FAVORABLE SE PORTION 
OF A BROAD UPPER TROUGH TO THE N. THE UPPER TROUGH AMPLIFIES 
BEYOND THAT...WITH THE LOW LIKELY WEAKENING. A LACK OF DEEP 
LAYER MOISTURE IS PREVENTING ANY MAJOR CONVECTIVE DEVELOPMENT 
NEAR THIS LOW PRES AREA PRESENTLY.

GULF OF TEHUANTEPEC...SCATTEROMETER PASSES HAVE NOT SAMPLED THE 
REGION WELL DURING THE PAST 12 HOURS...BUT WINDS ARE FORECAST BY 
ALL THE GLOBAL MODELS TO CONTINUE THROUGH ANOTHER 24 HOURS 
BEFORE DIMINISHING TO LESS THAN 20 KT BY 36 HOURS.

GULF OF PAPAGAYO...OVERNIGHT DRAINAGE FLOW WILL ENHANCE TO N-NE 
FLOW CURRENTLY PREVAILING ACROSS THE WRN CARIBBEAN. FRESH TO 
STRONG NORTHEASTERLY GAP WINDS ARE EXPECTED DURING THE NEXT 
COUPLE OF DAYS...WITH WINDS LIKELY STRONGEST DURING THE LATE 
NIGHT AND EARLY MORNING HOURS. 

$$
STRIPLING