000
AXPZ20 KNHC 181612 CCA
TWDEP 

TROPICAL WEATHER DISCUSSION...CORRECTED    
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC WED MAR 18 2009

...CORRECTED TO ADD MENTION OF QUIKSCAT DATA TO GAP WINDS...

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1600 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 3N79W TO 4N92W TO 2N110W TO 3N130W
6N104W. NO SIGNIFICANT CONVECTION IS NOTED.

...DISCUSSION...

N OF 20N...
A RATHER PROGRESSIVE UPPER LEVEL PATTERN IS EVIDENT ACROSS 
THE REGION WITH FIRST FEATURE NOTED BEING A SHORTWAVE TROUGH 
THAT EXTENDS FROM N OF THE AREA NEAR 27N135W SW TO A WEAK UPPER
LEVEL CYCLONIC CIRCULATION MOVING NE NEAR 32N134W. THE TROUGH
CONTINUES SE TO NEAR 22N128W. A MID/UPPER LEVEL RIDGE IS E OF
THE TROUGH...AND LIES ROUGHLY ALONG 26N122W TO N OF THE AREA
AT 32N122W. A SMALLER SHORTWAVE TROUGH...DAMPENING OUT WITH TIME
...IS E OF THIS RIDGE JUST ALONG THE NORTHERN BAJA CALIFORNIA AND
STRETCHING N TO ALONG THE SOUTHERN CALIFORNIA COAST. IT IS
MOVING INLAND.

THE FLOW PATTERN TO THE W OF THE TROUGH IS ZONAL AS A STRONG
JET STREAM STRETCHES W TO E ALONG 21N BETWEEN 130W AND
140W. LATEST GLOBAL MODEL GUIDANCE SUGGESTS THAT AN AMPLIFYING
SHORTWAVE TROUGH WILL DIVE SOUTHEASTWARD TOWARDS 30N BY THE
END OF THE WEEK ALLOWING FOR A WEAKENING COLD FRONT TO MOVE
THROUGH THE FAR NORTHERN WATERS. THIS FRONT SHOULD BRING
A SHORT-LIVED PERIOD OF N WINDS TO ABOUT 20 KT OVER THESE WATERS
WITH WAVEWATCH GUIDANCE INDICATING SEAS TO BUILD UP TO 10 FT OR
11 FT IN MAINLY A NW SWELL. THESE SWELLS WILL THEN SLOWLY SUBSIDE
TO 8 FT GOING INTO SAT. AT THE SURFACE...A 1027 MB HIGH IS N OF
THE AREA NEAR 34N132W. ITS IS FORECAST TO MOVE SW TO NEAR
32N135W AS A 1025 MB IN 24 HOURS.

S OF 20N...
A MID/UPPER LEVEL TROUGH EXTENDS FROM 16N118W TO 10N118W TO S OF
THE EQUATOR AT 117W. UPPER LEVEL DIVERGENCE TAKING PLACE FROM 
6N TO 15N BETWEEN 120W AND 127W IS SETTING OFF ISOLATED MODERATE
CONVECTION WITHIN 45 NM OF 12N125W...AND ISOLATED SHOWERS 
ELSEWHERE ELSEWHERE WITHIN THIS AREA. THE TROUGH IS CAUGHT IN 
BETWEEN TWO AREAS OF BROAD MID/UPPER LEVEL RIDGING IS OBSERVED 
ON WATER VAPOR IMAGERY. EXTENSIVE MID/UPPER LEVEL MOISTURE IN 
THE FORM OF OVERCAST TO BROKEN MOSTLY BLOW OFF CIRRUS CLOUDS IS 
NOTED OVER THE FAR WESTERN SECTION OF THE AREA FROM 7N TO 20N W 
OF 135W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING 
UNDER THESE CLOUDS. AT SURFACE...NE-E WINDS OF GENERALLY 15 KT 
ARE SEEN HERE WHILE LIGHTER WINDS ARE JUST S NEAR AND ALONG THE 
ITCZ. THIS IS ALSO SUPPORTING DEVELOPMENT OF SHOWERS AND TSTMS 
IN THIS AREA. THIS AREA WILL LIKELY REMAIN ACTIVE FOR ANOTHER 24 
HOURS AS UPPER LEVEL DIVERGENCE SHIFT FURTHER E.

A 1028 MB SURFACE HIGH WAS CENTERED N OF THE AREA NEAR 
34N131W...WITH THE ENHANCED SURFACE PRESSURE GRADIENT AT THE 
SOUTHERN PERIPHERY OF THIS FEATURE ENHANCING NE TO E TRADES 
ACROSS THE REGION...AND CONTRIBUTING TO THE BROAD LOW LEVEL 
CONVERGENCE ZONE DISCUSSED ABOVE. OLD NWLY SWELL CONTINUES TO 
PROPAGATE THROUGH MOST OF THE FORECAST AREA THIS MORNING...WITH 
HIGHEST SEAS NEAR 11 FT LOCATED WITHIN THIS BAND OF ENHANCED NE 
TO E TRADES...IN A MIX OF NW AND SW SWELL AND NELY WIND WAVES. 
AS THE UPPER FLOW N OF THE AREA AMPLIFIES...THE SURFACE HIGH IS 
EXPECTED TO WEAKEN DURING THE NEXT FEW DAYS. IN RESPONSE...TRADE 
WINDS WILL SLACKEN...WITH SEAS GRADUALLY SUBSIDING.

GAP WINDS...CORRECTED
GULF OF TEHUANTEPEC WINDS HAVE DIMINISHED TO 20 TO 25 KT PER 
QUIKSCAT DATA FROM NEAR 1200 UTC THIS MORNING. THESE WINDS ARE 
EXPECTED TO DECREASE TO LESS THAN 20 KT IN 36 HOURS...THEN 
INCREASE AGAIN TO 20 TO 25 KT IN 48 HOURS AS STRONG HIGH PRES
BUILDS S ACROSS SE MEXICO TO JUST N IF THE ISTHMUS OF THE 
GULF. TRADE WINDS ACROSS THE CARIBBEAN CONTINUE WITH A 
PERSISTENT SURFACE LOW OVER NW COLOMBIA. THESE WINDS CONTINUE TO 
BLEED INTO THE GULFS OF FONSECA AND PAPAGAYO AS NE WINDS OF
20 KT. THESE WINDS ARE FORECAST TO CONTINUE PERIODICALLY DURING 
THE NEXT FEW DAYS...WITH THE MAXIMUM WIND SPEEDS EXPECTED TO
OCCUR LATE NIGHT INTO THE MORNING HOURS. 

$$

AGUIRRE