000
AXPZ20 KNHC 130327
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SUN DEC 13 2009

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0300 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...07N77W TO 
08N90W TO 07N108W TO 07126W TO 07N140W. SCATTERED MODERATE 
CONVECTION IS FROM 05N TO 08N W OF 124W. 

...DISCUSSION... 

BROAD UPPER-LEVEL TROUGH WITH AXIS FROM NW MEXICO SW TO NEAR 
20N111W...OTHERWISE NEARLY ZONAL FLOW COVERS THE AREA N OF 20N W 
OF THE TROUGH. A 90-110 KT JETSTREAM IS JUST NORTH OF AREA 
CROSSING SOUTHERN CALIFORNIA...ARIZONA AND NEW MEXICO INTO 
TEXAS. SOME MID/UPPER LEVEL MOISTURE IS NOTED ON WATER VAPOR 
IMAGERY N OF 23N WHILE MODERATE TO STRONG SUBSIDENCE WITH DRY 
STABLE AIR AT THE MIDDLE AND UPPER LEVELS OF THE ATMOSPHERE 
DOMINATES THE AREA N OF THE ITCZ W OF 110W.

AN UPPER ANTICYCLONE CENTERED OVER THE NW CARIBBEAN EXTENDS A 
RIDGE ACROSS SE MEXICO AND MOST OF CENTRAL AMERICA INTO THE EPAC 
WHERE IS PRODUCING MODERATE TO STRONG SUBSIDENCE MAINLY E OF 
100W. THE SUBSIDENCE HAS SUPPRESSED ANY STRONG CONVECTION ALONG 
THE ITCZ. AN UPPER-LEVEL TROUGH IS IN THE DEEP TROPICS WITH AXIS 
FROM 12N100W TO A CYCLONIC CIRCULATION NEAR 04N97W.

A WEAKENING COLD FRONT IS MOVING ACROSS THE N WATERS STRETCHING 
FROM 30N125W TO 26N140W. WINDS HAVE DIMINISHED BELOW 20 KT 
EITHER SIDE OF THE FRONT WITH SEAS TO 8 FT BEHIND IT. THE FRONT 
WILL CONTINUE TO DISSIPATE DURING THE NEXT 12 TO 24 HOURS. E OF 
FRONT...A 1019 MB SURFACE HIGH IS CENTERED NEAR 26N118W. FRESH 
TO STRONG TRADE WINDS ON THE SOUTHERN PERIPHERY OF THIS HIGH ARE 
EVIDENT ON AN EARLIER ASCAT AND SOME SHIP OBSERVATIONS. LITTLE 
CHANGE IS EXPECTED OVER THE NEXT 48 HOURS.

A COUPLE OF TROUGH ARE ANALYZED ALONG THE ITCZ. THE FIRST AND 
BETTER DEFINED EXTENDS FROM 11N108W TO 05N110W. NE TO E WINDS OF 
20 KT ARE NOTED N OF 08 WITHIN 90 NM EITHER SIDE OF THE TROUGH 
AXIS PER THE MOST RECENT ASCAT PASS. MARINE GUIDANCE INDICATES 
THAT THIS TROUGH AND THE ASSOCIATED WIND PATTERN WILL PERSIST 
DURING THE NEXT 24 HOURS OR SO. A SECOND TROUGH GOES FROM 
11N126W TO 06N127W. A SLIGHTLY INCREASE IN CONVECTION IS SEEN 
ALONG THE ITCZ AXIS JUST W OF THIS TROUGH.  

LARGE AND LONG PERIOD NW SWELL CONTINUES TO SPREAD ACROSS THE 
REGION BEYOND THE EQUATOR. HOWEVER THE SEA HEIGHTS ARE 
SUBSIDING. A NEW BATCH OF NW SWELL WITH WAVE PERIODS BETWEEN 14 
TO 15 SECONDS SHOULD REACH THE FAR NW PORTION OF THE FORECAST 
AREA BY SUN EVENING. THIS SWELL EVENT WILL BE ASSOCIATED WITH A 
STRONG EXTRATROPICAL CYCLONE MOVING ACROSS THE NE PACIFIC. 

GAP WINDS...
NE TO E WINDS OF 20 TO 25 KT ARE BLOWING ACROSS THE GULF OF 
PAPAGAYO AS THE PRES GRADIENT BUILDS ACROSS THE WESTERN 
CARIBBEAN...ALLOWING ELY TRADE WINDS TO FUNNEL ACROSS COSTA RICA 
AND NICARAGUA INTO THE EASTERN PACIFIC. SHIP 9HJB9 NEAR 10N88W 
REPORTED NE WIND OF 24 KT AT 0100 UTC.

NLY WINDS OF 20 KT ARE STILL BLOWING ACROSS THE GULF OF 
TEHUANTEPEC. COMPUTER GUIDANCE SUGGESTS THAT THIS WIND EVENT 
WILL PERSIST ACROSS THIS AREA OVER THE NEXT COUPLE OF DAYS.  
  
$$
GR