000
AXPZ20 KNHC 151004
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC FRI MAY 15 2009

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0915 UTC.

...ITCZ...

THE ITCZ AXIS WAS ALONG LINE FROM 08N77W TO 08N87W TO 10N98W TO 
11N103W TO 10N110W TO 04N140W. SCATTERED TO NUMEROUS MODERATE 
WITH ISOLATED STRONG CONVECTION WAS OCCURRING WITHIN 300 NM S OF 
AXIS E OF 116W. ISOLATED TO SCATTERED MODERATE CONVECTION WAS 
OCCURRING WITHIN 240 NM N OF AXIS W OF 96W.

...DISCUSSION...

ALOFT...AN ELONGATED MID TO UPPER TROUGH EXTENDS NE TO SW ACROSS 
THE N PORTION OF THE DISCUSSION AREA...FROM 32N116W THROUGH TWO 
EMBEDDED VORTICES TO 21N140W AND BEYOND. AN UPSTREAM UPPER RIDGE 
TILTING NE WITH LATITUDE IS SPILLING INTO THE BACKSIDE OF THIS 
TROUGH TO PRODUCE CONVERGENCE IN DEEP SINKING MOTION. 
DOWNSTREAM...AN UPPER LEVEL ANTICYCLONE WAS CENTERED AT 
13N106W...WITH A RIDGE EXTENDING NE ACROSS OLD MEXICO AND INTO 
EXTREME SRN TEXAS...AND A SECONDARY RIDGE EWD INTO CENTRAL 
AMERICA AND NW COSTA RICA. ANOTHER UPPER RIDGE EXTENDS W ACROSS 
MOST OF NRN S AMERICA N OF THE EQUATOR. A BROAD UPPER TROUGH 
WITH CUT OFF LOW OVER THE CENTRAL BAHAMAS EXTENDS SW ACROSS THE 
WRN CARIBBEAN AND ACROSS PANAMA...AND SEPARATES THE FLOW 
ASSOCIATED WITH THE TWO ANTICYCLONES.

UPPER DIFFLUENCE ASSOCIATED WITH THE EPAC ANTICYCLONE CONTINUES 
TO ENHANCE CONVECTION ON BOTH SIDES OF THE ITCZ E OF 130W...AS 
WELL ACROSS SRN MEXICO. THIS RIDGE WILL REMAIN STATIONARY FOR 
THE NEXT FEW DAYS...AND BE SURROUNDED BY ZONES OF SINKING AIR 
ASSOCIATED WITH MID TO UPPER TROUGHS TO THE NW...S AND NE. THIS 
PATTERN IS EXPECTED TO MAINTAIN VERY FAVORABLE CONDITIONS FOR 
ACTIVE THUNDERSTORM ACTIVITY INVOF OF THE ITCZ AND ACROSS MUCH 
OF THE TROPICAL EPAC OVER THE NEXT FEW DAYS.
     
AT THE LOW LEVELS...A RIDGE EXTENDS SE FROM A 1027 MB HIGH NEAR 
34N135W TO 18N106W. THE GRADIENT NE OF THE RIDGE IS SUPPORTING 
NW TO N WINDS OF 20 TO 25 KT OFF THE COAST OF SRN CALIFORNIA AND 
THE BAJA...WITH THE SEAS EXPECTED TO MAX AT AROUND 14 FT THIS 
MORNING IN THE NW SWELL THROUGH THIS AFTERNOON...THEN THE 
GRADIENT SHOULD RELAX SOME...WITH A ZONE OF 20 KT WINDS SLIDING 
W AND FARTHER AWAY FROM THE COAST THROUGH SAT. AN ELONGATED AREA 
OF NE TRADES OF 20 KT CONNECTS WITH THIS AREA...AND EXTENDS SW 
TO THE ITCZ NEAR 140W. THESE WINDS WILL GRADUALLY DIMINISH TO 20 
KT OR LESS BY SAT.      

GAP WINDS...THE ITCZ HAS LIFTED N AND NEAR THE CENTRAL AMERICA 
COAST...WHICH IS HAVING A LIMITING EFFECT ON GAP WINDS INTO THE 
EPAC. A FRONTAL SYSTEM IS FORECAST TO MOVE INTO THE N AND NE 
GULF OF MEXICO...WITH POTENTIAL FOR A BROAD LOW PRESSURE CENTER. 
THIS MAY IN TURN INCREASE NLY WIND FLOW IN THE GULF OF 
TEHUANTEPEC TO 20 KT OR GREATER BY MON MORNING.

SEVERAL CYCLONIC CURLS ARE NOTED IN THE ACTIVE CONVECTION NEAR 
THE EPAC ITCZ...THE MOST NOTABLE ARE TWO AREAS OF LOW TO MID 
LEVEL TURNING A FEW DEGREES EITHER SIDE OF 110W. THIS GFS MODEL 
IS FORECASTING THE WRN MOST AREA TO BECOME BETTER ORGANIZED 
DURING THE NEXT SEVERAL DAYS. DUE TO ACTIVE AND PERSISTENT 
CONVECTION AND FAVORABLE UPPER LEVEL CONDITIONS...THIS AREA 
SHOULD BE WATCHED FOR POTENTIAL TROPICAL DEVELOPMENT.
$$

STRIPLING