000
AXPZ20 KNHC 291539
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC WED APR 29 2009

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 
1330 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE CAN BE FOUND ALONG THE LINE 
FROM...08N77W TO 04N97W TO 05N122W TO 03N133W TO 04N140W. 
SCATTERED MODERATE CONVECTION LIE WITHIN 120 NM S OF THE ITCZ 
AXIS FROM 81W TO 84W AND N OF THE ITCZ AXIS FROM 81W TO 86W. 
SCATTERED MODERATE CONVECTION CAN BE FOUND WITHIN 90 NM OF THE 
ITCZ AXIS FROM 91W TO 96W. SCATTERED MODERATE WITH ISOLATED 
STRONG CONVECTION IS WITHIN 90 NM N AND 120 NM S OF THE ITCZ 
AXIS W OF 118W.

 
...DISCUSSION...

N OF 20N...
1025 MB HIGH PRESSURE NEAR 34N128W IS CURRENTLY BOOKENDED TO THE 
W BY AN AMPLIFIED DEEP LAYER TROUGH AND ITS ASSOCIATED COLD 
FRONT MOVING INTO NW WATERS AND TO THE E BY A DEEP LAYER 
TROUGHING OVER THE SW U.S.  THE 1344 UTC QUIKSCAT PASS SHOWED 
WINDS TO 30 KT OFF THE BAJA COAST ON THE NE SIDE OF THE RIDGE 
AXIS.  THE SHIP PHFV CONFIRMED THESE WINDS...REPORTING 30 KT AT 
1200 UTC NEAR 25N113W.  THE PATTERN WILL BECOME HIGHLY 
PROGRESSIVE OVER N WATERS DURING THE NEXT FEW DAYS AS THE 
NORTHERN STREAM UPPER JET PUSHES THE DEEP LAYER TROUGH CURRENTLY 
E OF HAWAII N NORTHEASTWARD INTO THE W COAST OF NORTH AMERICA. 
THIS WILL WEAKEN THE SURFACE HIGH AND SHIFT IT 
SOUTHWARD...WEAKENING WINDS OFF BAJA CALIFORNIA THU NIGHT.  
WINDS ARE ALSO TO 30 KT IN ADVANCE OF THE COLD FRONT MOVING INTO 
NW WATERS ACCORDING TO THE 0414 UTC QUIKSCAT PASS.  THIS COLD 
FRONT SHOULD WEAKEN TO A FRONTAL TROUGH AND DISSIPATE N OF THE 
AREA OVER THE NEXT TWO DAYS.  THIS FRONT IT CURRENTLY TAPPED 
INTO TROPICAL MOISTURE AND IS SUPPORTING SOME WEAK CONVECTION 
OVER NW WATERS AT THIS TIME.

S OF 20N...
A LOW TO MID LEVEL TROUGH IS EMBEDDED WITHIN THE ITCZ FROM 
10N122W TO 06N125W TO 02N127W.  SCATTERED MODERATE CONVECTION 
LIES WITHIN 90 NM W AND 420 NM E OF AXIS FROM 07N TO 10N.  THE 
TROUGH IS ALSO ASSOCIATED WITH CONVECTION WITHIN 90 NM N AND 120 
NM S OF THE ITCZ AXIS W OF 118W.  TOTAL PRECIPITABLE WATER 
IMAGERY SHOWS A POOL OF 2.25 TO 2.50 INCH PRECIPITABLE WATER 
VALUES COINCIDING WITH THE TROUGH.  THE CONVECTION HAS BEEN 
ENHANCED BY THE UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THE 
ANTICYCLONE CENTERED NEAR 10N118W.  AS THE DEEP LAYER TROUGH 
OVER NW WATERS PUSHES EASTWARD...EXPECT THIS WEAK MID LEVEL 
TROUGH TO LIFT NE TOWARD THE DEEP LAYER TROUGH AXIS.  AT THE 
SAME TIME...THIS TROUGH WILL BATTLE THE SOUTHWARD DRIFTING HIGH 
PRES SYSTEM AT THE SURFACE TO ITS N.

TO THE E OF THE ANTICYCLONE...AN UPPER LEVEL TROUGH IS CENTERED 
ALONG 100W.  THE BROAD SOUTHWESTERLY JET ON THE EASTERN SIDE OF 
THE TROUGH PASSES THROUGH CENTRAL AMERICA AND INTO THE 
CARIBBEAN...WITH THE REAR RIGHT QUADRANT OF THE JET COINCIDING 
WITH THE ITCZ NEAR 05N85W.  STRONG LOW LEVEL CONVERGENCE OF 
MOISTURE ALONG THE ITCZ COUPLED WITH THE UPPER LEVEL DIFFLUENCE 
IS GENERATING CONVECTION ALONG THE ITCZ E OF 96W AS FAR N AS 
SOUTHERN COSTA RICA AND AS FAR S AS THE COAST OF NORTHERN 
ECUADOR.

GAP WINDS...
THE 1158 UTC QUIKSCAT PASS SHOWS NE WINDS TO 25 KT IN THE LEE OF 
THE GULF OF PAPAGAYO.  WINDS HERE ARE EXPECTED TO DIMINISH TO 
20 KT BY FRI MORNING AND FURTHER WEAKEN DURING THE DAY FRI AS 
THE TRADE WINDS IN THE CARIBBEAN DIMINISH AND TURN MORE EASTERLY.

$$
SCHAUER CLARK