000
AXPZ20 KNHC 151523
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI MAY 15 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 
1500 UTC.

...ITCZ...

THE ITCZ AXIS ALONG LINE FROM 08N78W TO 10N96W TO 14N105W TO 
09N120W TO 06N140W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION IS WITHIN 300 NM S OF AXIS E OF 96W. SCATTERED 
MODERATE CONVECTION IS FROM 06N TO 13N BETWEEN 98W AND 128W. 
CONVECTION WILL REMAIN ACTIVE DUE TO FAVORABLE UPPER LEVEL 
CONDITIONS. 

...DISCUSSION...

UPPER DIFFLUENCE ASSOCIATED IN PART WITH A RIDGE ALOFT 
OVER THE TROPICAL E PAC IS PROVIDING A MOIST ENVIRONMENT OVER A 
CONSIDERABLE PORTION OF THE DEEP TROPICS. LOW-LEVEL CONVERGENCE 
ALONG THE ITCZ...ENHANCED BY MORNING DRAINAGE FLOW NEAR THE 
COASTS OF CENTRAL AMERICA AND MEXICO...IS PRODUCING SCATTERED 
MODERATE CONVECTION WITHIN 120 NM OF THE COAST BETWEEN 88W AND 
102W. A LARGER AREA OF CONVECTION IS LOCATED ON EITHER SIDE OF 
THE ITCZ...OUTLINED ABOVE. THERE ARE A COUPLE OF PERTURBATIONS 
WITHIN THE ITCZ HELPING TO FOCUS THE CONVECTION. THE MOST 
NOTABLE ON SATELLITE IMAGERY ARE NEAR 110W AND 120W. SOME OF THE 
GLOBAL MODELS DEPICT SOME WEAK DEVELOPMENT OF THE FEATURE ALONG 
110W INTO A MORE PRONOUNCED TROUGH OR WEAK LOW OVER THE NEXT FEW 
DAYS. THE LARGE AREA OF CONVECTION IS EXPECTED TO CONTINUE AS 
THE UPPER PATTERN REMAINS DIFFLUENT.  

A 1026 MB SFC HIGH AND BROAD LOW PRES TROUGHING OVER MEXICO AND 
THE SW CONUS IS PRODUCING N-NW 20-25 KT WINDS OVER THE NE 
PORTION OF THE ZONE...N OF 25N BETWEEN 117W AND 125W. WIND WAVES 
COMBINED WITH N SWELL IS ELEVATING SEAS TO 8-12 FT IN THE 
OUTLINED AREA. TOPOGRAPHIC VARIATIONS ARE ALSO ASSISTING IN 
ACCELERATING NW FLOW WITHIN 90 NM OF THE BAJA COAST AS REVEALED 
IN EARLIER ASCAT DATA. NE TRADES ARE MAINLY 15-20 KT ACROSS MUCH 
OF THE REMAINDER OF THE AREA W OF ABOUT 120W.

WIDESPREAD STABLE AIR IS NOTED OVER MUCH OF THE SUBTROPICS 
EMBEDDED WITHIN AN ELONGATED UPPER TROUGH EXTENDING FROM THE N 
GULF OF CALIFORNIA TO 20N140W. GLOBAL MODELS ARE IN GOOD 
AGREEMENT IN SHOWING AN UPPER LOW DEVELOPING AND CUTTING OFF 
FROM THE PROGRESSIVE FLOW THIS WEEKEND. AN ASSOCIATED WEAK SFC 
TROUGH IS EXPECTED TO DEVELOP...WHICH WILL WEAKEN THE TRADES AND 
ENHANCED WINDS OFF THE BAJA COAST THIS WEEKEND AND INTO EARLY 
NEXT WEEK.

GAP WINDS...THE COMBINATION OF A FRONTAL SYSTEM MOVING S INTO 
THE GULF OF MEXICO WITH STRONG HIGH PRES DEVELOPING N OF IT OVER 
THE CENTRAL CONUS AND A BROAD TROUGH OF LOW PRESSURE OVER THE SE 
GULF IS EXPECTED TO INCREASE NLY FLOW TO 20-25 KT OVER THE GULF 
OF TEHUANTEPEC BY MON MORNING AND LIKELY CONTINUING FOR AT LEAST 
A DAY OR TWO. 

$$
CANGIALOSI