000
AXPZ20 KNHC 232203
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU APR 23 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.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 5N77W 7N88W 3N100W 3N110W 5N120W
5N130W 4N140W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS 
WITHIN 60 NM EITHER SIDE OF THE AXIS BETWEEN 79W-90W. SCATTERED
MODERATE CONVECTION IS WITHIN 120 NM S OF THE AXIS BETWEEN 
93W-95W.

...DISCUSSION...

MID/UPPER LEVEL RIDGE EXTENDS FROM THE SW U.S. INTO THE AREA
THROUGH 32N119W AND CONTINUES TO 24N122W TO 15N125W TO 6N125W.
THIS FEATURE CONTINUES TO BE THE MOST PREDOMINATE IN THE AREA
SEPARATING THE REGION FROM TROUGHS TO ITS E AND W. THE FIRST  
TROUGH IS W OF 140W APPROXIMATELY ALONG 146W...AND EXTENDS NNE
TO A LARGE UPPER LEVEL CYCLONIC VORTEX NEAR 35N144W. AN 
ASSOCIATED WEAKENING SURFACE FRONTAL TROUGH EXTENDS FROM 32N137W 
TO 25N140W. BROKEN TO OVERCAST LOW/MID CLOUDS WITH WIDELY 
SCATTERED SHOWERS ARE WITHIN 45 NM OF THE TROUGH. THIS TROUGH 
WILL SLOWLY WASH OUT OVER THE FAR NW WATERS THROUGH FRI. THE 
MID/UPPER TROUGH OVER THE ERN PART OF THE AREA EXTENDS INTO THE 
AREA FROM THE CENTRAL U.S. TO NW MEXICO AND THEN SW TO 22N109W 
TO 16N112W TO 8N114W. THIS TROUGH IN COMBINATION WITH AN 
EASTERLY SURGE APPROACHING 120W FROM 4N-12N IS TRIGGERING OFF 
SCATTERED MODERATE CONVECTION WITHIN 30 NM OF LINE 10N112W TO 
10N114W TO 10N117W. THE RIDGE WILL MIGRATE EWD TO MEXICO OVER 
THE NEXT 48 HRS...WITH THE TROUGH TO ITS W FLATTENING OUT AS THE 
ATTENDANT CYCLONIC VORTEX BEGINS TO TRACK NE AND BECOME DIFFUSE. 
THE UPPER FLOW GENERALLY BECOMES SW AS ANOTHER LARGE CYCLONIC 
VORTEX DEVELOPS JUST TO THE NW OF THE REGION BY SAT WITH A 
TROUGH DIGGING SWD.

SWLY UPPER FLOW TO THE E OF THE TROUGH W OF THE REGION IS 
ADVECTING EXTENSIVE UPPER LEVEL MOISTURE IN THE FORM OF BROKEN 
HIGH CLOUDINESS NEWD UP AND OVER THE RIDGE. THE MOSITURE IS 
REACHING AS FAR E AS 124W. SWLY FLOW ALSO PRESENT E OF THE ERN 
TROUGH IS ADVECTING SCATTERED TO BROKEN HIGH CLOUDS NEWD TOWARDS 
SE MEXICO. OUTSIDE ITCZ CONVECTION OVER THE FAR ERN PORTION OF 
THE AREA...MODERATE SUBSIDENCE WITH ASSOCIATED STABLE 
ENVIRONMENTAL CONDITIONS ARE OBSERVED. ONLY SCATTERED LOW CLOUDS 
WITH POSSIBLE ISOLATED SHOWERS MOVING WSW UNDER NE WIND FLOW ARE 
OBSERVED WITHIN THIS SECTOR OF THE AREA.

AT THE SURFACE...A 1021 MB HIGH CENTERED NEAR 27N133W EXTENDS A 
RIDGE SE TO 19N110W. HIGH PRES COVERS THE AREA N OF 14N AND W OF 
110W. HIGH PRES IS FORECAST TO STRENGTHEN LATE FRI INTO SAT 
ALLOWING FOR THE PRES GRADIENT TO TIGHTEN OVER THE NE WATERS
LEADING TO AN INCREASE IN NW WINDS NEAR THE BAJA CALIFORNIA
COAST.

A WEAK SURFACE TROUGH ALONG 96W/97W IS MOVING SLOWLY W...AND IS
PERIODICALLY ENHANCING ITCZ CONVECTION IN THAT VICINITY.

BROKEN TO OVERCAST STRATOCUMULUS CLOUDS ARE NOTED NW OF LINE
FROM 26N114W TO 19N121W TO 15N138W.

GAP WINDS...
NE WINDS OF 20-25 KT IN THE GULF OF PAPAGAYO ARE FORECAST TO 
CHANGE LITTLE OVER THE NEXT 48 HRS WITH SEAS IN THE 8 TO 10 FT 
RANGE.

$$
AGUIRRE