000
AXPZ20 KNHC 041551
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SUN DEC 04 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 
1515 UTC.

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

THE MONSOON TROUGH ENTERS THE EPAC NEAR 05N77W TO 07N83W TO 
05N98W THEN TRANSITIONS TO ITCZ TO LOW PRES 1010 MB NEAR 09N107W 
TO 06N115W TO WEAK LOW PRES 1011 MB NEAR 11N123W TO 07N140W. 
SCATTERED MODERATE CONVECTION IS NOTED FROM 04N TO 07N E OF 81W 
...AND FROM 08N TO 10N BETWEEN 104W AND 107W.   

...DISCUSSION...

IN THE UPPER LEVELS...THE BASE OF A SHARP UPPER LEVEL TROUGH IS 
OVER N MEXICO ...BAJA CALIFORNIA... AND THE PACIFIC... N OF 20N 
BETWEEN 100W AND 130W. A 70-90 KT UPPER LEVEL JETSTREAM IS OVER 
THE AREA. WATER VAPOR IMAGERY INDICATES VERY DRY AIR AND 
RELATIVELY STABLE CONDITIONS ALOFT WITH THIS UPPER LEVEL 
FEATURE. ELSEWHERE BROAD UPPER LEVEL RIDGES ARE FOUND BOTH TO 
THE W AND SE OF THE UPPER LEVEL TROUGHING...ONE WITH AN AXIS 
ALONG 140W AND THE OTHER CENTERED IN THE DEEP TROPICS NEAR 
08N95W EXTENDING N-NE TO THE YUCATAN PENINSULA.

A 1018 MB LOW IS OVER SW ARIZONA WITH TROUGHING EXTENDING SW 
ACROSS NRN BAJA CALIFORNIA TO 29N120W. A 1042 MB HIGH ACROSS THE 
NE PACIFIC NEAR 46N137W IS COMBINING WITH THIS LOW PRES OFF OF 
NRN BAJA CALIFORNIA TO PRODUCE FRESH NE WINDS N OF 28N W OF 
132W...AND THEN S OF THE HIGH TO THE ITCZ...FROM 12N TO 20N W OF 
125W...WHILE NE WINDS TO NEAR 20 KT PREVAILED THERE BETWEEN 20N 
AND 28N. SEAS OF 8 TO 11 FT PREVAIL ACROSS THIS AREA IN A MIX OF 
N AND NEW NW SWELL.

NLY 20 KT WINDS ARE OVER THE FAR N PORTIONS OF THE GULF OF 
CALIFORNIA. A TIGHTENING OF THE SURFACE PRESSURE GRADIENT IS 
FORECAST FOR THE NEXT 48 HOURS INCREASING WINDS TO 25 KT IN THE 
GULF OF CALIFORNIA N OF 21N. A SECOND AND STRONGER SURGE OF NW 
WINDS IS EXPECTED TUE AND WED...WITH WINDS 20 TO 30 KT...AND 
POSSIBLY REACHING GALE FORCE. SEAS WILL BUILD TO 8 FT AND HIGHER 
ACROSS PORTIONS OF THE GULF DURING THIS TIME.

TO THE SE...A 1010 MB LOW PRES CENTER REMAINS EMBEDDED WITHIN 
THE ITCZ NEAR 09N107W MOVING W AT AROUND 10 KT. 20 TO 25 KT 
WINDS ARE WITHIN 150 NM ACROSS THE NRN SEMICIRCLE OF THE LOW 
PRES. GLOBAL MODELS SUGGEST THE LOW PERSISTING AT LEAST THROUGH 
72 HOURS AS IT SHIFTS WNW AT AROUND 10 KT. 

GULF OF TEHUANTEPEC...DRAINAGE FLOW THROUGH THE CHIVELA PASS 
SHOULD KEEP WINDS AT 20 KT THROUGH THE MORNING HOURS THEN 
SYNOPTIC SCALE FORCING SHOULD ALLOW WINDS TO DROP TO LIGHT AND 
VARIABLE THEREAFTER AS SLY RETURN FLOW HAS BECOME ESTABLISHED 
ACROSS THE WRN GULF OF MEXICO. A COLD FRONT FORECAST TO MOVE 
THROUGH THE W GULF OF MEXICO LATE MON AND TUE WILL RE-INITIATE 
NLY WINDS THROUGH THE GULF OF TEHUANTEPEC BEGINNING EARLY 
TUE...WITH THE POSSIBILITY OF MINIMAL GALES THERE BY TUE NIGHT.

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

$$
FORMOSA