000
AXPZ20 KNHC 140327
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC MON SEP 14 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 
0315 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS ANALYZED ALONG 98W N OF 7N TO INLAND SE 
MEXICO MOVING W AT 15 KT. WEAK ISOLATED TSTMS ARE WITHIN 30 NM 
OF 15N98W.

A TROPICAL WAVE IS ANALYZED ALONG 111W/112W FROM 5N-17N MOVING W 
10 KT. LATEST SATELLITE IMAGERY SHOWS THAT THE WAVE IS PART OF
A LARGE AREA OF DISORGANIZED MULTILAYERED CLOUDS WITH CONVECTION
AS DESCRIBED BELOW UNDER ITCZ. ISOLATED SHOWERS AND TSTMS ARE 
ALONG AND WITHIN 30 NM OF THE AXIS FROM 14N-17N. BEING THAT THE
WAVE IS NOW UNDER A DIFFLUENT UPPER PATTERN...AND THIS WHOLE AREA
OF CLOUDS AND CONVECTION IS BASICALLY TIED INTO A LARGE MONSOONAL
CIRCULATION GENERALLY BETWEEN 98W-112W EXPECT CONVECTION TO
CONTINUE IN INTERMITTENT BURSTS THROUGH THE NEXT 48 HOURS.

...THE ITCZ...

ITCZ AXIS IS CENTERED ALONG 8N79W TO 15N97W TO 13N112W TO 
10N123W TO 10N130W TO 10N140W. SCATTERED STRONG CONVECTION
IS WITHIN 60 NM S OF THE AXIS BETWEEN 121W-125W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120 NM S OF THE
AXIS BETWEEN 131W-133W...AND ALSO S OF THE AXIS FROM 6N-9N
BETWEEN 115W-118W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM 
S OF THE AXIS BETWEEN 112W-115W.

...DISCUSSION...

A SHARPENING MID TO UPPER TROUGH MOVING E NEAR 25 KT ENTERS THE 
AREA THROUGH 32N123W AND EXTENDS SW TO 26N133W...THEN BECOMES 
ILL DEFINED TO BEYOND THE AREA AT 26N140W. THE TROUGH IS 
SUPPORTING A RATHER WEAK COLD FRONT THAT LAGS BEHIND IT...AND 
ENTERS THE AREA THROUGH 32N124W TO 28N130W WHERE IT BECOMES 
RATHER WEAK TO 28N140W. THE AREA IS DRY AND CLOUD FREE IN THE 
MIDDLE AND UPPER LEVELS WITH BROKEN STRATOCUMULUS IN THE LOWER 
LEVELS. THE TROUGH IS FORECAST TO MOVE E AND BE REPLACED BY 
NEAR ZONAL FLOW IN THE NEXT DAY OR TWO. THE COLD FRONT IS 
FORECAST TO DISSIPATE IN ABOUT 24 HOURS AS HIGH PRES BUILDS
S INTO THE N CENTRAL PORTION OF THE AREA. LONG PERIOD NWLY 
SWELLS HAVE ALREADY SPREAD SEWD INTO THE NORTHERN PORTION OF
THE AREA BEHIND THE FRONT ALLOWING FOR SEAS OF UP TO 10 FT.
THESE SWELLS WILL GRADUALLY SUBSIDE THROUGH THE NEXT 24 HOURS.
A STRONGER COLD FRONT...PRESENTLY WELL NW OF THE AREA...IS 
FORECAST TO APPROACH THE FAR NW CORNER OF THE AREA TUE PRECEDED
BY INCREASING SLY WINDS AND BUILDING SEAS. LATEST WAVEWATCH 
MODEL INDICATIONS ARE THAT LARGE LONG PERIOD NW SWELLS WITH THIS 
SECONDARY FRONT SHOULD STAY N OF THE AREA AS THE MAIN ENERGY 
SOURCE PASSES THE REGION.

TO THE SE OF THE ABOVE TROUGH...THE MID/UPPER FLOW BECOMES
RATHER ZONAL AS MID/UPPER LEVEL RIDGING IS ALONG 18N WITH 
THE UPPER LEVEL ANTICYCLONE NEAR 19N109W MOVING SLOWLY E.
THE SURFACE PRES PATTERN REMAINS WEAK...WHILE THE 
REMNANT LOW OF LINDA CONTINUES TO BE OBSERVED AS A VERY 
PRONOUNCED CIRCULATION NEAR 20N134W WITH A PRES OF 1009 MB. A 
WEAK RIDGE IS BETWEEN THE REMNANT LOW AND THE ABOVE COLD FRONT.
THE REMNANT LOW CIRCULATION COVERS THE AREA FROM 16N TO 
24N...AND BETWEEN 130W AND 137W. IT IS VOID OF DEEP 
CONVECTION...AND CONSISTS OF BROKEN TO SCATTERED LOW CLOUDS WITH 
POSSIBLE ISOLATED SHOWERS. A SHIP OBSERVATION WITH CALLER ID 
"LAZU5" JUST SW OF THE CIRCULATION NEAR 19N134W REPORTED 
COMBINED SEAS OF 10 FT IN A NW SWELL AT 0000 UTC. WINDS OF 20 KT 
ARE OCCURRING WITHIN 180 NM IN THE NORTHERN SEMICIRCLE OF THE 
LOW. THE LOW IS FORECAST TO WEAKEN INTO A TROUGH WITHIN THE NEXT 
36 TO 48 HOURS OVER THE FAR WESTERN PORTION OF THE AREA W OF 
135W.

A DEEP MOISTURE PLUME ORIGINATING FROM BOTH ITCZ CONVECTION 
...AND CONVECTION NEAR THE TROPICAL WAVE ALONG 111W/112W 
CONTINUES TO BE ADVECTED WESTWARD ALONG THE SRN PERIPHERY OF THE 
MID/UPPER RIDGE...AND AROUND ITS WESTERN PERIPHERY THEN ERODES
NEAR 122W WHERE THE ENVIRONMENT BECOMES DRY AND STABLE NOTED
AS MODERATE SUBSIDENCE IN WATER VAPOR IMAGERY FROM THROUGHOUT 
THE DAY.

QUIKSCAT DATA FROM THIS MORNING VIVIDLY DISPLAYED A LARGE SWATH 
OF SLY WINDS OF 20-25 KT OVER THE SRN PORTION OF THE AREA S OF 
ABOUT 10N AND E OF 132W. THESE WINDS ARE INFLOWING INTO THE 
DISTURBED AREA OF WEATHER ASSOCIATED WITH THE MONSOONAL 
CIRCULATION MENTIONED ABOVE UNDER TROPICAL WAVE AIDING IN STRONG 
LOW LEVEL  CONVERGENCE. SEAS WITHIN THIS AREA ARE IN THE 8-11 FT 
RANGE...BUT ARE EXPECTED TO BUILD UP TO 12 FT IN MIXED SE AND
SW SWELLS IN 24 HOURS.

GLOBAL MODELS ARE KEYING IN ON THE DEVELOPMENT OF POSSIBLY THE 
NEXT LOW PRES SYSTEM AS THE CROSS HEMISPHERIC FLOW MAINTAINS THE 
E END OF MONSOON TROUGH/ITCZ N TO ALONG THE MEXICAN AND CENTRAL 
AMERICAN COAST DURING THE NEXT 48 HOURS.

$$
AGUIRRE