000
AXPZ20 KNHC 181533
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC THU AUG 18 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...SPECIAL FEATURES...
TROPICAL STORM FERNANDA HAS MOVED WEST OF THE DISCUSSION AREA 
AND INTO CENTRAL PACIFIC HURRICANE BASIN. AT 18/1500 UTC...IT IS 
LOCATED NEAR 13.7N 141.0W. REFER TO FORECAST ADVISORIES ISSUED 
UNDER WMO HEADER WTPA21 PHFO AND AWIPS HEADER HFOTCMCP1 FOR 
FURTHER DETAILS.

HURRICANE GREG CENTERED NEAR 18.5N 111.5W AT 18/1500 UTC MOVING 
WEST NORTHWEST OR 285 DEGREES AT 16 KT. A TURN TOWARD THE WEST 
WITH A DECREASE IN FORWARD SPEED IS FORECAST DURING THE NEXT 
COUPLE OF DAYS. MAXIMUM SUSTAINED WIND SPEED IS 75 GUSTS TO 90 
KT. GREG IS A CATEGORY ONE HURRICANE ON THE SAFFIR-SIMPSON 
HURRICANE WIND SCALE. SOME ADDITIONAL STRENGTHENING IS POSSIBLE 
TODAY...WITH A WEAKENING TREND FORECAST TO BEGIN ON FRIDAY. 
ESTIMATED MINIMUM CENTRAL PRESSURE IS 980 MB. NUMEROUS STRONG 
WITHIN 90 NM NE SEMICIRCLE AND 150 NM SW SEMICIRCLE. REFER TO 
FORECAST ADVISORIES ISSUED UNDER WMO HEADER WTPZ22 KNHC AND 
AWIPS HEADER MIATCMEP2 FOR FURTHER DETAILS.

...ITCZ/MONSOON TROUGH...
MONSOON TROUGH ANALYZED FROM 10N83W TO 08N91W TO 13N99W...THEN 
RESUMES FROM 17N113W TO 11N127W TO 13N131W. SCATTERED TO STRONG 
WITHIN 180 NM N OF AXIS FROM 117W TO 119W.

...DISCUSSION...
UPPER LEVEL TROUGH ACROSS THE FAR NW PORTION OF THE DISCUSSION 
AREA WITH AXIS CROSSING 30N139W TO 27N140W. AN ANTICYCLONIC 
CIRCULATION IS NEAR 28N121W WITH A RIDGE TO THE SW TO 17N135W. 
A WEAK UPPER LEVEL INVERTED TROUGH FROM CENTRAL BAJA TO A 
CYCLONIC CIRCULATION NEAR 24N115W SEPARATES THE ABOVE MENTIONED 
ANTICYCLONE FROM ANOTHER ANTICYCLONIC CIRCULATION OVER THE SW 
CONUS. GREG IS MOVING AROUND THE SOUTHERN PERIPHERY OF THIS   
LARGE MID/UPPER-LEVEL RIDGE OVER THE SW UNITED STATES AND 
NORTHWESTERN MEXICO. 

A 1029 MB HIGH PRES LOCATED N OF AREA NEAR 42N136W EXTENDS A 
RIDGE OVER THE FORECAST WATERS MAINLY N OF 20N W OF 115W. AN 
EARLIER ASCAT PASS SHOWED THE CYCLONIC CIRCULATION ASSOCIATED 
WITH FERNANDA. FRESH TO STRONG WINDS ASSOCIATED WITH THIS 
TROPICAL CYCLONE CONTINUE TO AFFECT THE FORECAST WATERS FROM 10N 
TO 18N W OF 136W.  

THE CROSS EQUATORIAL SLY SWELL HAS SUBSIDED. 

$$
GR