000
AXPZ20 KNHC 101523
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SUN MAY 10 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 
1300 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE LIES ALONG A LINE FROM 07N77W 
TO 07N97W TO 09N108W TO 05N125W TO 05N140W. SCATTERED MODERATE 
CONVECTION CAN BE FOUND WITHIN 180 NM N OF AXIS FROM 82W TO 
85W....WITHIN 120 NM S OF AXIS FROM 87W TO 100W...WITHIN 75 M N 
OF AXIS FROM 93W TO 95W....AND WITHIN 150 NM N OF AXIS W OF 131W.

...DISCUSSION...
UPPER LEVEL SOUTHERLY FLOW TO 50 KT AROUND 110W TO 115W IS 
DIRECTING TROPICAL MOISTURE AND HIGH CLOUDS NORTH-NORTHEASTWARD 
INTO CENTRAL MEXICO. THIS UPPER JET IS WEDGED BETWEEN A 
WEAKENING UPPER LOW NEAR 22N119W AND AN ANTICYCLONE NEAR 
14N100W. WITHIN 600 NM SW QUADRANT OF THE UPPER LOW IS MARKED BY 
STRONG SUBSIDENCE WHILE THE EASTERN SEMICIRCLE IS INTERCEPTING 
SOME OF THE NORTHWARD MOVING MID TO UPPER LEVEL MOISTURE. A 
SURFACE TROUGH EMBEDDED IN THE ITCZ FROM 12N111W TO 04N116W 
COINCIDES WITH THE REAR RIGHT QUADRANT OF THE AFOREMENTIONED 
UPPER JET. THE TROUGH POSITION IS EVIDENT IN THE 1352 QUIKSCAT 
PASS. SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION CAN BE 
FOUND BETWEEN 04N AND 07N E OF THE TROUGH AXIS TO 110W AND 
WITHIN 120 NM W OF THE TROUGH AXIS AS WELL AS W OF THE TROUGH 
FROM 02N TO 05N BETWEEN 118W AND 123W. THE JET WILL NUDGE 
NORTHWESTWARD AS THE UPPER LOW TO ITS WEST WEAKENS AND JOINS 
WITH THE WEAK UPPER TROUGH CURRENTLY OVER NW WATERS...LEAVING A 
BROAD NEGATIVELY TILTED UPPER TROUGH OVER FORECAST WATERS W OF 
100W MON. THE SURFACE TROUGH SHOULD ALSO NUDGE WESTWARD OVER THE 
NEXT DAY OR TWO. THE DISRUPTION OF THE DEEP LAYER EASTERLY FLOW 
OVER W CENTRAL WATERS BY THIS TROUGH...IN ADDITION TO THE 
PROGRESSIVE PATTERN N OF FORECAST WATERS...HAS CAUSED THE TRADE 
WINDS TO DIMINISH.

TO THE S OF THE UPPER LEVEL ANTICYCLONE NEAR 14N100W LIES AN 
UPPER LOW NEAR 00N92W WITH A RIDGE AXIS EXTENDING N TO 09N87W. 
CONFLUENT FLOW BETWEEN THESE UPPER FEATURES IS INHIBITING THE 
DEVELOPMENT OF DEEP CONVECTION ALONG THE ITCZ W OF THE SURFACE 
TROUGH FROM 100W TO 110W. FARTHER E...DIFFLUENCE BETWEEN THIS 
ANTICYCLONE AND THE ANTICYCLONE OVER NORTHERN SOUTH AMERICA HAS 
ALLOWED FOR SCATTERED MODERATE CONVECTION TO DEVELOP ALONG THE 
COAST OF COSTA RICA AND WESTERN PANAMA N OF THE ITCZ.

OVER NE WATERS...DENSE LOW LEVEL CLOUDINESS CAN BE FOUND ALONG 
THE COAST OF BAJA CALIFORNIA IN THE VICINITY OF THE CALIFORNIA 
CURRENT. OFFSHORE...20 KT N WINDS ARE EVIDENT ON THE ASCAT PASS 
FROM 0556 UTC N OF 24N BETWEEN 123W AND 130W. THE STRONG 
PRESSURE GRADIENT CURRENTLY IN PLACE BETWEEN TROUGHING OVER THE 
SW U.S. AND NW MEXICO AND THE 1028 MB HIGH PRESSURE SYSTEM NEAR 
34N134W WILL WEAKEN OVER FORECAST WATERS...ALONG WITH THE 
WINDS...AS THE HIGH WEAKENS AND SHIFTS NORTHWARD. 
HOWEVER...STRONG WINDS FARTHER N ALONG THE CA COAST WILL 
CONTINUE TO BRING NORTHERLY SWELL TO NE WATERS.

GAP WINDS...THE 1214 UTC QUIKSCAT PASS SHOWS WINDS DOWNWIND OF 
THE GULF OF PAPAGAYO HAVE REACHED 20 TO 25 KT. THE RETURN OF 
STRONG TRADE WINDS IN THE SW CARIBBEAN HAS ALLOWED EASTERLY FLOW 
TO BLEED THROUGH NORTHERN COSTA RICA AND SOUTHERN NICARAGUA. 
WHILE THE STRENGTH OF THE FLOW WILL LIKELY PULSE...WITH A 
MAXIMUM IN THE EARLY MORNING HOURS...WINDS ARE EXPECTED TO 
REMAIN 20 KT AND ABOVE HERE FOR THE NEXT FEW DAYS.

$$
SCHAUER CLARK