000
AXPZ20 KNHC 300241
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC MON JUL 30 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0230 UTC.

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

THE MONSOON TROUGH IS ALONG 09N78W TO 09N90W TO 09N105W. THE 
INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 09N105W TO 
11N115W TO 10N124W TO 08N140W. SCATTERED MODERATE AND ISOLATED 
STRONG CONVECTION IS FROM 06N TO 10N E OF 87W. SIMILAR 
CONVECTION IS FROM 09N TO 12N BETWEEN 97W AND 100W.

...DISCUSSION...

A LARGE BLOCKING MIDDLE TO UPPER LEVEL RIDGE OVER THE CENTRAL 
U.S. ALONG ABOUT 102W CONTINUES TO PRODUCE A STAGNANT UPPER 
PATTERN ACROSS MUCH OF THE DISCUSSION AREA. A MIDDLE TO UPPER 
LEVEL CYCLONE NEAR 26N124W REMAINS NEARLY STATIONARY...WITH A 
TROUGH EXTENDING NE TO THE SOUTHERN CALIFORNIA COAST...AND ALSO 
SW TO NEAR 17N133W. UPPER RIDGING GENERALLY PREVAILS TO THE E OF 
THIS FEATURE TO CENTRAL MEXICO AND N OF 21N. UPPER LEVEL 
EASTERLIES ARE FOUND S OF 14N W OF 95W...YIELDING LIGHT WIND 
SHEAR AND FAVORABLE UPPER CONDITIONS FOR SPORADIC DEEP 
CONVECTION. ELSEWHERE E OF 95W...WEAK UPPER LEVEL RIDGING 
PERSISTS...AND RECENT SCATTERED CONVECTION NEAR THE MONSOON 
TROUGH HAS AIDED IN MAINTAINING DIFFLUENT FLOW ALOFT OVER THAT 
REGION.

AT LOWER LEVELS...SURFACE HIGH PRES REMAINS CENTERED NW OF THE 
AREA NEAR 35N136W WITH A RIDGE EXTENDING SE FROM THE HIGH TO 
18N109W. THE RESULTING PRES GRADIENT BETWEEN THIS RIDGE AND 
LOWER PRES NEAR THE ITCZ IS PRODUCING A ZONE OF 20-25 KT NE-E 
TRADES FROM 12N TO 21N W OF 133W ALONG WITH SEAS TO 9 FT SEAS. 
THESE CONDITIONS WILL NOT CHANGE MUCH IN AREAL COVERAGE AND 
INTENSITY THROUGH THE NEXT 24-48 HOURS.

NE-E 20-25 KT WINDS WILL CONTINUE TO PULSE IN AND DOWNWIND OF 
THE GULF OF PAPAGAYO THROUGH EARLY TUE...DIMINISHING BY TUE 
EVENING. THESE WINDS ARE ATTEMPTING TO INDUCE A TROUGH OR LOW IN 
THE LOW LEVELS ALONG THE MONSOON TROUGH NEAR 95/96W AS INDICATED 
BY AN EARLIER RECENT ASCAT PASS. ACTIVE CONVECTION WILL CONTINUE
ALONG AND E OF THIS FEATURE AS IT DRIFTS W DURING THE NEXT 
COUPLE OF DAYS.

A SUFFICIENT PRES GRADIENT EXISTS BETWEEN HIGH PRES ACROSS THE 
GULF OF MEXICO AND THE MONSOON TROUGH S-SW OF CENTRAL AMERICA 
RESULTING IN N-NE 20-25 KT WINDS THROUGH THE GULF OF TEHUANTEPEC 
AND DOWNSTREAM/SW ABOUT 180 NM. THE DEVELOPING TROUGH/LOW NEAR 
95W/96W MENTIONED ABOVE WITH HELP TO MAINTAIN THIS FLOW THROUGH 
MON AFTERNOON...WITH WINDS DECREASING TO 20 KT OR LESS TUE 
AFTERNOON.

A MIDDLE LEVEL CYCLONIC CIRCULATION NEAR 18N110W CONTINUES TO 
OCCASIONALLY INDUCE PULSING CONVECTION IN ITS VICINITY AS IT 
DRIFTS W. SCATTERED MODERATE CONVECTION IS FROM 18N TO 20N 
BETWEEN 109W AND 112W. A SURFACE TROUGH ASSOCIATED WITH THE 
FEATURE ALOFT EXTENDS FROM 22N110W TO 17N109W. THIS TROUGH WILL 
DRIFT W AND WEAKEN THROUGH THE NEXT 48 HOURS AS IT ENCOUNTERS 
GRADUALLY COOLER OCEAN WATERS AND MORE STABLE ATMOSPHERIC 
CONDITIONS.

CROSS-EQUATORIAL SOUTHERLY SWELL WILL BREACH THE S CENTRAL/SW 
BORDER BY TUE AFTERNOON WITH 8 FT SEAS EXPECTED S OF 04N BETWEEN 
110W AND 125W IN SW SWELL. ALSO...LATEST MODEL GUIDANCE NO 
LONGER SHOWS 8 FT NORTHERLY SWELL MAKING IT S OF 30N AND THIS 
FEATURE HAS NOW BEEN REMOVED FROM THE FORECAST.

$$
LEWITSKY