000
AXPZ20 KNHC 122205
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SAT SEP 12 2009

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2145 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS ROUGHLY ALONG 109W FROM 5N-18N MOVING W ABOUT
18 KT. LATEST SATELLITE IMAGERY IS SHOWING SCATTERED STRONG 
CONVECTION E OF THE WAVE FROM 8N-12N BETWEEN 100W-109W. THE WAVE 
HAS MOVED UNDER AN UPPER PATTERN THAT HAS BECOME SOMEWHAT 
DIFFLUENT LEAVING BEHIND AN UPPER ENVIRONMENT OF ELY SHEAR. ONLY 
ISOLATED SHOWERS AND SMALL WEAK TSTMS ARE ELSEWHERE WITHIN 180 
NM E OF THE WAVE.

A TROPICAL WAVE IS ANALYZED ALONG 87W N OF 4N TO ACROSS HONDURAS
...AND INTO THE GULF OF HONDURAS MOVING W AT 15 KT. ONLY DEEP
CONVECTION NEAR THIS WAVE IS THAT WHICH IS DESCRIBED BELOW UNDER
ITCZ.

...THE ITCZ...

ITCZ AXIS IS CENTERED ALONG 8N79W TO 13N92W TO 15N106W TO 8N120W
TO 6N130W TO 5N140W. SCATTERED MODERATE TO STRONG CONVECTION IS
WITHIN 90 NM S OF THE ITCZ BETWEEN 101W-105W. SCATTERED MODERATE
/ISOLATED STRONG CONVECTION IS WITHIN 180 NM S OF THE AXIS E OF 
87W.

...DISCUSSION...

AN UPPER LEVEL ANTICYCLONE NEAR 21N115W MOVING SLOWLY SE HAS
AN ASSOCIATED RIDGE EXTENDING SW TO 18N128W TO A SMALL 
ANTICYCLONE NEAR 13N135W AND TO W OF THE AREA AT 13N140W. 
ANOTHER RIDGE EXTENDS RIDGE EXTENDS SE FROM THE ANTICYCLONE TO 
19N105W TO ALONG THE MEXICAN COAST NEAR 16N96W. THE ANALYZED 
SURFACE RIDGE EXTENDS SE INTO THE AREA THROUGH 28N140W SE TO 
NEAR 25N124W. THE REMNANT LOW OF LINDA CONTINUES TO BE OBSERVED 
AS A VERY PRONOUNCED CIRCULATION CENTERED NEAR 21N132W WITH A 
PRES OF 1011 MB. IT IS VOID OF DEEP CONVECTION...AND CONSISTS OF 
BROKEN TO SCATTERED LOW CLOUDS WITH ISOLATED SHOWERS PRIMARILY 
WITHIN 150 NM OF THE CENTER IN THE NORTHERN SEMICIRCLE. A 
QUIKSCAT PASS FROM NEAR 1500 UTC THIS MORNING NICELY CAPTURED 
THE CYCLONIC CIRCULATION WITH THE LOW REVELING 20-30 KT WINDS 
WITHIN ABOUT 220 NM OF THE CENTER IN THE N SEMICIRCLE WITH 
THE HIGHER RANGE OF THESE WINDS NW OF THE CENTER. WINDS OF
20 KT WERE NOTED WITHIN 120 NM IN THE SE QUADRANT. SEAS OF
8-11 FT ARE ASSOCIATED WITH THESE WINDS.

A DEEP MOISTURE PLUME ORIGINATING FROM BOTH ITCZ CONVECTION
...AND CONVECTION NEAR THE TROPICAL WAVE ALONG 109W CONTINUES
TO BE ADVECTED WESTWARD ALONG THE SRN PERIPHERY OF THE RIDGE TO 
NEAR 127W WHERE IT ERODES IN A DRIER AND STABLE ENVIRONMENT
AROUND THE ABOVE ANTICYCLONE AND RIDGE. THIS STABLE ENVIRONMENT
IS NOTED AS MODERATE SUBSIDENCE IN WATER VAPOR IMAGERY FROM
THROUGHOUT THE DAY.

A DEEP LAYER TROUGH MOVING RAPIDLY E HAS MOVED INTO THE 
FAR NW SECTION OF THE REGION...AND EXTENDS FROM 32N135W TO 
28N140W. WATER VAPOR IMAGERY SHOWS A 180 NM WIDE MOISTURE
PLUME WITH THE TROUGH...AND STRETCHING ENE OVER THE CREST 
OF THE ANTICYCLONE NEAR 21N115W WITH A TRAJECTORY TOWARDS
THE U.S. WEST COAST AND FAR NRN BAJA CALIFORNIA. THE ASSOCIATED 
SURFACE COLD FRONT IS JUST NW OF THE AREA. THE TROUGH IS 
FORECAST BY NWP MODELS TO REACH THE FAR NE PORTION OF THE AREA 
SUN NIGHT INTO MON WHILE THE COLD FRONT BEGINS TO WEAKEN AS IT 
REACHES A LINE FROM 32N127W TO 27N140W SUN...AND DISSIPATE BY 
MON MORNING. LONG PERIOD NWLY SWELLS WILL FLOW INTO THE NW 
PORTION OF THE AREA SUN ALLOWING FOR SEAS TO MAX OUT UP TO 10 OF 
11 FT PER LATEST WAVE MODEL GUIDANCE. THESE SWELLS WILL THEN 
SUBSIDE SUN NIGHT. A STRONGER COLD FRONT...PRESENTLY WELL NW OF 
THE AREA...IS FORECAST TO MOVE INTO THE FAR NW PORTION OF THE 
AREA LATE MON NIGHT INTO 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.

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 9N AND E OF 125W. WITHIN THIS AREA OF WINDS SEAS OF 8-12 
FT IN MIXED SE AND SW SWELLS...MUCH OF IT GENERATED BY PERSISTENT
SE WINDS OF 20-25 KT S OF THE AREA...CAN BE EXPECTED THROUGH AT 
LEAST THE NEXT 48 HOURS.

BEYOND 48 HOURS IN THE TROPICAL ZONE....GLOBAL MODELS ARE KEYING
IN ON THE POSSIBLE NEXT LOW DEVELOPING BETWEEN 102W AND 110W IN
RELATION TO THE TROPICAL WAVE.

$$
AGUIRRE