000
AXPZ20 KNHC 191607
TWDEP 

TROPICAL WEATHER DISCUSSION      
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT MAY 19 2012

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...SPECIAL FEATURES...

AT 1500 UTC...ALETTA WAS DOWNGRADED TO A POST-TROPICAL 
CYCLONE...CENTERED NEAR NEAR 14.8N 112.5W MOVING ENE OR 065 DEG 
AT 4 KT. THE ESTIMATED MINIMUM CENTRAL PRES REMAINED AT 1006 MB. 
MAXIMUM SUSTAINED WINDS WERE 25 KT GUSTS TO 35 KT. PLEASE REFER 
TO THE LATEST PUBLIC ADVISORY TCPEP1/WTPZ31 KNHC FOR MORE 
DETAILS. CONVECTION HAS CONTINUED TO DECREASE AROUND THE 
PERIPHERY OF THE CENTER...WITH ISOLATED MODERATE CONVECTION 
NOTED BETWEEN 60 NM AND 90 NM ACROSS THE N QUADRANT. WATER VAPOR 
IMAGERY SHOWS DRY AIR HAS WRAPPED AROUND THE SYSTEM. THE 
REMNANTS OF ALETTA ARE FORECAST TO DISSIPATED WITHIN 48 HOURS.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

THE MONSOON TROUGH AXIS EXTENDS FROM 11N84W TO LOW PRES NEAR 
11N100W TO 10N105W...WHERE IT BREAKS...THEN RESUMES NEAR 12N111W 
TO 06N128W...WHERE IT TRANSITIONS TO ITCZ...CONTINUING ON TO 
02N140W. SCATTERED MODERATE WITHIN 120 NM SE OF AXIS BETWEEN 
110W AND 112W. SCATTERED TO NUMEROUS MODERATE TO STRONG WITHIN 
180 NM OF LOW PRES NEAR 11N100W. NUMEROUS MODERATE TO STRONG 
FROM 06N TO 13N BETWEEN 90W AND 98W. NUMEROUS MODERATE TO STRONG 
WITHIN 180 NM OF THE PACIFIC COAST BETWEEN 80W AND 90W. 
SCATTERED MODERATE ISOLATED STRONG IN GULF OF PANAMA S OF 04N.

...DISCUSSION...

INFRARED SATELLITE IMAGERY SHOWED NUMEROUS MODERATE TO STRONG 
CONVECTION WITHIN 180 NM OF A LOW PRES SYSTEM NEAR 11N100W. THE 
0636 UTC OSCAT PASS SHOWED FRESH SW WINDS IN THE AREA S OF THE 
LOW FROM 04N TO 08N BETWEEN 96W AND 102W. THIS BROAD AREA OF LOW 
PRES LIES UNDER AN UPPER RIDGE THAT STEMS FROM AN ANTICYCLONE 
OVER THE GULF OF FONSECA. THE LOW TO MEANDER SLOWLY S TO SW OVER 
THE NEXT TWO DAYS...AND REMAIN IN AN AREA OF DEEP TROPICAL 
MOISTURE. MEANWHILE...THE RIDGE ALOFT IS EXPECTED TO PINCH OF A 
SECOND ANTICYCLONE W OF THE SURFACE LOW NEAR 12N108W SUN...WITH 
WEAK TROUGHING BUILDING BETWEEN THE ANTICYCLONES AND OVER THE 
SURFACE LOW SUN INTO MON. THE BUILDING TROUGHING OVER THE LOW 
SHOULD INHIBIT ANY FAST DEVELOPMENT OF THIS SYSTEM. THERE IS A 
LOW CHANCE OF THIS SYSTEM DEVELOPING INTO A TROPICAL CYCLONE 
OVER THE NEXT 48 HOURS. 

RIDGING ALOFT ASSOCIATED WITH A MEAN UPPER ANTICYCLONE CENTERED 
OVER THE GULF OF FONSECA PREVAILS S OF 18N AND SPANS BETWEEN 65W 
AND 114W. LIGHT WIND SHEAR ALONG THE S SIDE OF THE RIDGE AND 
DEEP CONVECTIVE TOWERS ASSOCIATED WITH PULSING CONVECTION S OF 
THE MONSOON TROUGH ARE PRODUCING A ZONE OF FAVORABLE UPPER 
DIVERGENCE ALOFT...AND AIDING TO MAINTAIN THIS RIDGING CENTERED 
DUE NORTH OF THE STRONGEST CONVECTION. PRECIPITABLE WATER VALUES 
IN THIS REGION RANGE IN THE 2.0-2.5 INCH BETWEEN 90W AND 102W. 
THE VERTICAL LIFT OF THIS MOISTURE IS ENHANCING THE NUMEROUS 
MODERATE TO STRONG CONVECTION IS ALSO FOUND UNDERNEATH THE UPPER 
RIDGE FROM 06N TO 13N BETWEEN 90W AND 98W AND WITHIN 180 NM OF 
THE PACIFIC COAST BETWEEN 80W AND 90W.

THE 0308 UTC ASCAT PASS SHOWED N WINDS TO 25 KT IN THE GULF OF 
TEHUANTEPEC. NORTHERLY FLOW THROUGH ISTHMUS OF TEHUANTEPEC IS 
BEING FORCED BY THE PRES GRADIENT BETWEEN RIDGING IN THE WESTERN 
GULF OF MEXICO AND STATIONARY TROUGHING OVER THE E COAST OF THE 
YUCATAN PENINSULA. THIS SHORT PLUME OF NLY FLOW IS EXPECTED TO 
CONTINUE ACROSS THE GULF OF TEHUANTEPEC DURING THE NEXT 24 HOURS 
THEN INCREASE TO A FRESH TO STRONG BREEZE BY SUN MORNING AS HIGH 
PRES OVER THE U.S. GULF COAST STATES RETROGRADES WESTWARD... 
INCREASING THE RIDGING OVER THE WESTERN GULF OF MEXICO.

THE SUBTROPICAL RIDGE CONTINUES TO WEAKEN OVER NORTH WATERS AND 
TRADE WINDS ARE DOWN TO A GENTLE TO MODERATE BREEZE CONFINED TO 
WATERS W OF 130W. THE ASSOCIATED HIGH PRES CENTER IS CURRENTLY 
JUST N OF WESTERN WATERS. THE HIGH WILL CONTINUE TO WEAKEN AS IT 
IS SQUEEZED SOUTHEASTWARD AHEAD OF A FRONT OVER THE NEXT TWO 
DAYS. THE PRES GRADIENT WILL REMAIN STRONG ENOUGH ON THE E SIDE 
OF THE HIGH TO GENERATE A MODERATE TO FRESH N BREEZE WELL OFF 
THE BAJA PENINSULA OVER NE WATERS ...WITH NORTHERLY SWELL 
KEEPING SEAS IN THE 7-9 FT RANGE THERE INTO MON MORNING.

$$
STRIPLING