000
AXPZ20 KNHC 202154
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SAT AUG 20 2011

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 
2145 UTC.

...SPECIAL FEATURE...
TROPICAL STORM GREG NEAR 19.9N 120.5W AT 20/2100 UTC MOVING WNW 
OR 285 DEG AT 08 KT. MAXIMUM SUSTAINED WINDS ARE 35 KT GUSTS TO 
45 KT WITH AN ESTIMATED MINIMUM CENTRAL PRESSURE OF 1006 MB. 
GREG IS EXPECTED TO WEAKEN TO A TROPICAL DEPRESSION TONIGHT AND 
BECOME A POST-TROPICAL REMNANT LOW ON SUN. ALTHOUGH GREG 
CONTINUES TO SHOW GOOD ORGANIZATION THE DEEP CENTRAL CONVECTION 
HAS DECREASED IN AREAL COVERAGE. REFER TO FORECAST ADVISORIES 
ISSUED UNDER WMO HEADER WTPZ22 KNHC AND AWIPS HEADER MIATCMEP2 
FOR FURTHER DETAILS.

...ITCZ/MONSOON TROUGH...
FROM 11N86W TO 15N96W TO 1010 MB LOW PRES AT 13N104W TO 10N111W 
THEN FROM 17N123W TO 10N137W TO 10N140W.  SCATTERED MODERATE 
WITHIN 180 NM S OF AXIS E OF 109W AND SE OF AXIS FROM 123W TO 
128W.

...DISCUSSION...
TROPICAL STORM GREG HAS MAINTAINED IS INTENSITY THROUGHOUT THE 
DAY DESPITE TRAVERSING OVER COOLER WATERS. AN 1806 UTC ASCAT
SCATTEROMETER PASS DIRECTLY OVER THE CENTER SHOWED 35 KT WINDS 
NEAR THE CENTER WITH HIGHEST WINDS IN THE N SEMICIRCLE. DEEP 
CONVECTION HAS CONTINUED TO DECREASE IN COVERAGE EXTENDING OUT 
TO ONLY 45 NM WITHIN THE S AND 30 NM IN THE N SEMICIRCLES.
THE ASCAT PASS AS WELL AS GLOBAL MODEL GUIDANCE INDICATED A TAIL 
OF SW WINDS OF 20-25 KT AND ENHANCED SEAS EXTENDING S AND SE OF 
THE CENTER. THESE CONDITIONS ARE LIKELY THROUGH SUN GIVEN THE 
EMBEDDED SW MONSOON FLOW ALREADY IN PLACE. EXPECT GREG TO 
DISSIPATE COMPLETELY WITHIN 60 TO 72 HOURS WITH THE LOW LEVEL 
CENTER EVENTUALLY BEING ABSORBED IN THE LARGER SCALE CYCLONIC 
MONSOON CIRCULATION ACROSS THE REGION.

THE LOW PRES NEAR 13N104W SHOWS SOME CYCLONIC TURNING IN THE 
MOST RECENT VISIBLE SATELLITE IMAGES OF THE DAY. THE LOW IS 
EXPECTED TO REMAIN EMBEDDED IN THE MONSOON TROUGH AS THE TROUGH 
GRADUALLY LIFTS NORTHWARD THROUGH MON. SW WINDS OF 20-25 KT WITH 
SEAS TO 9 FT ASSOCIATED WITH THIS LOW IN THE MONSOON TROUGH 
THROUGH MON.

THE AREA OF WEAK LOW PRESSURE EMBEDDED EARLIER WITHIN THE 
MONSOON TROUGH IN THE GULF OF TEHUANTEPEC NEAR 15.5N94W HAS 
SINCE DISSIPATED. THERE WERE ONLY MINIMAL IMPACTS ON THE WINDS 
AND SEAS ASSOCIATED WITH THE AREA OF LOW PRES.  

OTHERWISE VERY LITTLE OF NOTE ACROSS THE DISCUSSION AREA. WINDS 
WILL INCREASE TO 15-20 KT ALONG THE NORTHERN BAJA PENINSULA... 
PUSHING SEAS TO 6-7 FT BY MON. LONG PERIOD CROSS EQUATORIAL 
SWELLS OF 15-17 SEC WILL PUSH NORTHWARD ACROSS THE EAST PACIFIC 
E OF 115W WITH SEAS REMAINING NEAR 8 FT NEAR THE EQUATOR.

$$
COBB