000
AXPZ20 KNHC 171536
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT DEC 17 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...

THE MONSOON TROUGH AXIS IS FROM 08N81W TO 07N89W TO 05N100W. 
ITCZ AXIS EXTENDS FROM 05N100W TO 09N116W TO 07N127W TO BEYOND 
07.5N140W. SCATTERED MODERATE CONVECTION WAS NOTED WITHIN 120 NM 
OF AXIS BETWEEN 112W AND 123W. SCATTERED MODERATE ISOLATED 
STRONG CONVECTION WAS NOTED WITHIN 120 NM N AND 90 NM S OF AXIS 
W OF 132W. 

...DISCUSSION...

AN UPPER LEVEL LOW IS CENTERED OVER THE FAR NE PART OF THE AREA 
WITH ASSOCIATED 1015 MB SURFACE LOW PRES CENTERED NEAR 29N117W. 
THE UPPER LOW WILL SHIFT E OF THE AREA SUN MORNING. WITH THE 
LOSS OF ITS UPPER LEVEL SUPPORT...THE SURFACE LOW WILL DISSIPATE 
BY SUN MORNING. 

A DISSIPATING COLD FRONT ASSOCIATED WITH A WEAKENING DEEP LAYER 
TROUGH WILL APPROACH NW WATERS TODAY AND USHER IN A NEW ROUND OF 
NW SWELL...WITH SEAS REACHING 10-12 FEET TONIGHT OVER THE NW 
PART OF THE AREA. THE PRESSURE GRADIENT BETWEEN DISSIPATING HIGH 
PRES 1026 MB CENTERED NEAR 33N136W AND LOWER PRESSURE IN THE 
VICINITY OF THE ITCZ IS MAINTAINING FRESH TRADEWINDS 08N TO 20N 
W OF 130W. NEW HIGH PRES MOVING IN BEHIND THE FRONT WILL MERGE 
ON SUN WITH THE HIGH PRES MENTIONED ABOVE...WHICH WILL RESULT IN 
EXPANDING COVERAGE OF FRESH TRADES...SPREADING EASTWARD TO 113W 
THROUGH MON MORNING.

GAP WINDS...
GULF OF TEHUANTEPEC...STRONG TO NEAR GALE WINDS ARE CURRENTLY 
OVER THE GULF OF TEHUANTEPEC...WITH WINDS EXPECTED TO REACH GALE 
FORCE BY THIS EVENING. WHILE THERE IS NO STRONG...PROGRESSIVE 
COLD FRONT EXPECTED TO SWEEP THROUGH THE GULF OF MEXICO TO 
INCREASE WINDS THROUGH THE ISTHMUS OF TEHUANTEPEC...THE BUILDING 
PRES GRADIENT BETWEEN HIGH PRES PASSING SE OVER THE SOUTHERN 
PLAINS AND LOWER MISSISSIPPI VALLEY AND LOWER PRES ALONG THE 
MONSOON TROUGH TO THE S WILL BE ENOUGH TO INITIATE GALE FORCE 
WINDS. WINDS WILL DIMINISH BELOW GALE FORCE OVERNIGHT SUN NIGHT 
AS THE HIGH PRES SHIFTS EASTWARD. 

GULF OF PAPAGAYO...THE BUILDING PRES GRADIENT OVER SOUTHERN 
MEXICO HAS EXTENDED S TO THE GULF OF PAPAGAYO WITH FRESH TO 
STRONG WINDS NOTED. THE FRESH TO STRONG WINDS ARE EXPECTED TO 
REMAIN WILL REMAIN OVER THE GULF OF PAPAGAYO THROUGH MON...THEN 
DIMINISH BELOW 20 KT AS HIGH PRES TO THE N SHIFTS EASTWARD.

$$
AL