000
AXPZ20 KNHC 291533
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH EXTENDS FROM LOW PRES OVER COLOMBIA 1006 MB NEAR 
09N75W TO 08.5N86W TO 09N108W...WHERE IT TRANSITIONS TO 
ITCZ...CONTINUING TO 10N116W TO 09N130W TO BEYOND 06N140W. 
SCATTERED MODERATE TO STRONG CONVECTION NOTED WITHIN 180 NM N 
AND 270 NM S OF TROUGH E OF 100W. SCATTERED MODERATE CONVECTION 
NOTED WITHIN 210 NM N OF ITCZ AXIS BETWEEN 100W AND 113W...AND 
WITHIN 150 NM N OF AXIS W OF 123W. SCATTERED MODERATE ISOLATED 
STRONG CONVECTION NOTED FROM 09N TO 13.5N BETWEEN 115W AND 125W. 
SCATTERED MODERATE CONTINUES TO PULSE WITHIN 90 NM OF 18N109W.
SCATTERED MODERATE TO STRONG NOTED FROM 11.5N TO 15N BETWEEN 94W 
AND 105W.

...DISCUSSION...
LARGE BLOCKING MIDDLE/UPPER LEVEL RIDGE OVER THE CENTRAL U.S. 
ALONG ABOUT 104W CONTINUES TO PRODUCE A STAGNANT UPPER PATTERN 
ACROSS MUCH OF THE DISCUSSION AREA. MIDDLE/UPPER LEVEL CYCLONE 
NEAR 24N123W REMAINS NEARLY STATIONARY...WITH TROUGH EXTENDING 
NE TO SRN CALIFORNIA COAST...AND SW TO NEAR 17N130W. UPPER 
RIDGING GENERALLY PREVAILS TO THE E OF THIS FEATURE TO CENTRAL 
MEXICO AND N OF 24N. UPPER LEVEL EASTERLIES ARE FOUND S OF 15N W 
OF 95W...YIELDING LIGHT WIND SHEAR AND FAVORABLE UPPER 
CONDITIONS FOR DEEP CONVECTION. E OF 95W WEAK UPPER RIDGING 
PERSISTS...AND RECENT NUMEROUS CONVECTION NEAR THE MONSOON 
TROUGH HAS AIDED IN MAINTAINING DIFFLUENT FLOW ALOFT THERE.

AT LOWER LEVELS...SURFACE HIGH PRES REMAINS CENTERED JUST NW OF 
THE AREA ALONG 36N. THE RESULTING PRES GRADIENT BETWEEN THIS 
RIDGE ACROSS THE NW PORTION OF THE AREA AND LOWER PRES NEAR THE 
ITCZ IS PRODUCING A ZONE OF 20-25 KT ELY WINDS FROM 11N TO 21N W 
OF 132W...WHERE SEAS WERE 8-10 FT AS VERIFIED BY AN OVERNIGHT 
ALTIMETER PASS. THESE CONDITIONS WILL SHIFT SLIGHTLY W AND 
PERSIST THROUGH EARLY TUE...AS SEAS DROP TO 7-9 FT.

A WIND SURGE PRODUCING ELY WINDS TO 25 KT CONTINUES TO BLOW 
THROUGH THE GULF OF PAPAGAYO AND DOWNSTREAM TO 93W. THIS IS 
HELPING TO PRODUCE A WAVE OR LOW IN THE LOW LEVELS...AND ALONG 
THE MONSOON TROUGH NEAR 95/96W. ACTIVE CONVECTION WILL CONTINUE 
ALONG AND E OF THIS WAVE AS IT DRIFTS W DURING THE NEXT COUPLE 
OF DAYS. THIS 20 KT GAP WIND FLOW IS EXPECTED TO CONTINUE 
THROUGH TUE MORNING. 

SUFFICIENT PRES GRADIENT EXISTS BETWEEN HIGH PRES ACROSS THE 
GULF OF MEXICO AND SOUTHERN MEXICO AND THE MONSOON TROUGH TO 
PRODUCE N TO NE WINDS TO 25 KT THROUGH THE GULF OF TEHUANTEPEC 
AND DOWNSTREAM ABOUT 200 NM. THE WAVE OR LOW ALONG THE MONSOON 
TROUGH TO THE S OF THIS AREA WILL HELP TO MAINTAIN THIS FLOW 
THROUGH MON...BEFORE WINDS DECREASE TO BELOW 20 KT TUE 
AFTERNOON.

A MIDDLE LEVEL CYCLONIC CIRCULATION NEAR 18N108W CONTINUES TO 
INDUCE PULSING CONVECTION IN ITS VICINITY AS IT DRIFTS W. AN 
OVERNIGHT WINDSAT PASS DID NOT SUGGEST ANY ASSOCIATED SURFACE 
LOW WITH THIS MID LEVEL FEATURE. THIS AREA OF WEATHER WILL DRIFT 
W AND WEAKEN OVER THE NEXT 48 HOURS...AS IT ENCOUNTERS GRADUALLY 
COOLER OCEAN WATERS AND MORE STABLE ATMOSPHERIC CONDITIONS. 

$$
STRIPLING