000
AXPZ20 KNHC 292140
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SUN JUL 29 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

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

THE MONSOON TROUGH IS ALONG 08N78W TO 08N90W TO 06N101W. THE 
INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 06N101W TO 
10N115W TO 09N130W TO 07N140W. SCATTERED MODERATE CONVECTION IS 
FROM 03N TO 05N E OF 87W...AND ALSO N OF 06N BETWEEN 79W AND 
84W. SIMILAR CONVECTION IS FROM 12N TO 15N BETWEEN 95W AND 
102W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 
09N TO 11N BETWEEN 111W AND 113W.

...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 CENTRAL CALIFORNIA COAST...AND ALSO 
SW TO NEAR 18N132W. UPPER RIDGING GENERALLY PREVAILS TO THE E OF 
THIS FEATURE TO CENTRAL MEXICO AND N OF 23N. UPPER LEVEL 
EASTERLIES ARE FOUND S OF 16N 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 
20N112W. 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 11N TO 19N W OF 134W ALONG WITH SEAS 8 TO 10 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 DURING THE NEXT 24-48 HOURS. THESE WINDS 
ARE ATTEMPTING TO INDUCE A TROUGH OR LOW IN THE LOW LEVELS ALONG 
THE MONSOON TROUGH NEAR 95/96W AS INDICATED BY A RECENT ASCAT 
PASS. ACTIVE CONVECTION WILL CONTINUE ALONG AND E OF THIS 
FEATURE AS IT DRIFTS W DURING THE NEXT COUPLE OF DAYS...WHILE 
THE NE-E WINDS IN THIS GENERAL AREA PERSIST.

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 240 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. EARLIER SCATTEROMETER PASSES DID NOT SUGGEST ANY 
ASSOCIATED SURFACE LOW WITH THIS MID LEVEL FEATURE. THIS AREA OF 
WEATHER WILL DRIFT W AND WEAKEN THROUGH THE NEXT 48 HOURS AS IT 
ENCOUNTERS GRADUALLY COOLER OCEAN WATERS AND MORE STABLE 
ATMOSPHERIC CONDITIONS.

NORTHERLY 8 FT SWELL WILL ATTEMPT TO SEEP TO 29N BETWEEN 120W 
AND 127W MON MORNING...SUBSIDING TO LESS THAN 8 FT BY TUE 
MORNING. ALSO...CROSS-EQUATORIAL SOUTHERLY SWELL WILL BREACH THE 
S CENTRAL/SW BORDER BY TUE AFTERNOON WITH 8 FT SEAS EXPECTED S 
OF 03N BETWEEN 105W AND 125W IN SW SWELL.

$$
LEWITSKY