000
AXPZ20 KNHC 301004
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1030 UTC THU AUG 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0930 UTC.

...SPECIAL FEATURE...

HURRICANE ILEANA WAS CENTERED AT 19.7N 113.5W AT 30/0900 UTC 
MOVING NW OR 325 DEG AT 08 KT AROUND THE W PERIPHERY OF AN UPPER 
RIDGE THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 987 MB. MAXIMUM 
SUSTAINED WIND SPEED IS 65 KT WITH GUSTS TO 80 KT. ILEANA IS 
EXHIBITING QUITE A SYMMETRICAL APPEARANCE WITH TIGHT BANDING 
RAIN BAND FEATURES ON SATELLITE IMAGERY. THE RAIN BAND CONSISTS 
OF LARGE CLUSTERS OF NUMEROUS STRONG CONVECTION NOTED WITHIN 150 
NM SE AND 90 NM NW OF THE CENTER. SCATTERED MODERATE/ISOLATED 
STRONG CONVECTION IS ELSEWHERE WITHIN 180 NM SE AND NW 120 NM OF 
THE CENTER. ILEANA IS FORECAST TO BEGIN TO MOVE OVER COOLER SEA 
SURFACE TEMPERATURES DURING THE NEXT 24-48 HRS...AND WILL BE 
FORECAST TO WEAKEN TO A TROPICAL STORM BY LATE FRI NIGHT NEAR 
21.5N 115.0W AS IT TRACKS IN A NW DIRECTION. SEE THE LATEST NHC 
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP4/WTPZ24 KNHC 
FOR MORE DETAILS.

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

THE MONSOON TROUGH EXTENDS FROM NW COLOMBIA WNW ACROSS THE 
CARIBBEAN TO THE PACIFIC COAST OF NORTHERN COSTA RICA AND 
CONTINUES TO 11N100W WHERE THE TROUGH LOSES IDENTITY IN THE 
BROAD CYCLONIC CIRCULATION ASSOCIATED WITH TROPICAL CYCLONE 
ILEANA. THE MONSOON TROUGH THEN BECOMES ESTABLISHED AGAIN SW OF 
ILEANA NEAR 14N116W AND CONTINUES SW TO 10N126W THEN WESTWARD TO 
BEYOND 11N140W. NUMEROUS STRONG CONVECTION IS WITHIN 180 NM N OF 
THE MONSOON TROUGH E OF 94W AND WITHIN 120 NM N OF THE TROUGH 
BETWEEN 97W-101W. SCATTERED STRONG CONVECTION IS WITHIN 360 NM S 
OF THE MONSOON TROUGH E OF 94W AND WITHIN 120 NM S OF THE TROUGH 
BETWEEN 94W-101W. SCATTERED MODERATE CONVECTION IS WITHIN 30 NM 
OF MONSOON TROUGH BETWEEN 116W AND 123W.

...DISCUSSION...

AN UPPER LEVEL TROUGH IS MOVING OVER THE NW COAST OF THE CONUS 
AND CONTINUES SW INTO A WEAKENING UPPER LEVEL CYCLONE NEAR 
34N130W...WITH THE TROUGH CONTINUING SW INTO THE DISCUSSION AREA 
TO A BASE AT 27N133W WITH CLOUD MOTION WINDS DETECTING A 
WESTERLY UPPER JET AT 50 TO 85 KT TO THE W OF THE TROUGH AXIS. 
BROAD MID/UPPER LEVEL RIDGING COVERS THE AREA TO THE W OF THE 
TROUGH. AT THE SURFACE...A RIDGE ENTERS THE AREA THROUGH 32N139W 
AND CONTINUES SE TO NEAR 25N126W. HIGH PRES COVERS THE AREA N OF
20N W OF 125W. NE SURFACE WINDS ARE EXPECTED TO CONTINUE INTO
FRI NIGHT AT 15-20 KT SW OF THE RIDGE AXIS IN THE AREA FROM 12N 
TO 16N W OF 133W...WITH SEAS 7 TO 9 FT IN NE SWELL SUBSIDING
TO LESS THAN 8 FT FRI NIGHT.

AN UPPER LEVEL ANTICYCLONE IS OVER COLORADO WITH AN UPPER RIDGE 
EXTENDING SW INTO THE DISCUSSION AREA TO 31N119W. ANOTHER UPPER 
ANTICYCLONE IS CENTERED NEAR 17N132W.

AN ILL-DEFINED UPPER CYCLONE IS OBSERVED AT 30N120W WITH AN 
UPPER TROUGH EXTENDING S THROUGH 20N122W INTO A SMALL UPPER 
CYCLONE AT 14N125W. MOST OF THE DEBRIS MOISTURE FROM ILEANA IS 
ADVECTED SW TO ALONG 08N BETWEEN 111W AND 124W...BUT SOME 
MOISTURE IS ALSO FANNING OUT IN THE UPPER ANTICYCLONIC FLOW N OF 
ILEANA ACROSS THE SOUTHERN BAJA PENINSULA AND GULF OF 
CALIFORNIA. OTHERWISE...THE UPPER LEVELS APPEAR VERY DRY TO THE 
W OF A LINE EXTENDING FROM THE BAJA PENINSULA AT 25N111W TO THE 
EQUATOR AT 130W. 

AN UPPER CYCLONE IS QUASI STATIONARY OVER THE NW CARIBBEAN AT 
19N80W WITH AN UPPER TROUGH EXTENDING S ACROSS EASTERN PANAMA TO 
BASE OVER COLOMBIA AT 07N76W. AN UPPER ANTICYCLONE...ASSOCIATED 
WITH ATLANTIC TROPICAL CYCLONE ISSAC...IS OVER THE N CENTRAL 
GULF OF MEXICO WITH AN UPPER RIDGE EXTENDING SW ACROSS OLD 
MEXICO TO A BROAD CREST OVER THE TROPICAL PACIFIC NEAR 13N100W. 
THE UPPER DIFFLUENCE BETWEEN THE CARIBBEAN UPPER CYCLONE AND 
THIS UPPER RIDGE IS SUPPORTING CONVECTION OVER CENTRAL AMERICA 
AND THE TROPICAL PACIFIC AS PREVIOUSLY DESCRIBED. THE RESULTANT 
DENSE UPPER DEBRIS MOISTURE IS ADVECTED SW TO ALONG 02N BETWEEN 
82W AND 108W.

ELSEWHERE AT THE LOW LEVELS...SOUTHWESTERLY MONSOONAL FLOW AT 
20-25 KT WINDS WITH SEAS 8 TO 11 FT ARE OBSERVED FROM 12N TO 19N 
BETWEEN 106W AND 117W...MERGING WITH THE SOUTHERLY WINDS OVER 
THE S SEMICIRCLE OF TROPICAL STORM ILEANA. 

GLOBAL MODELS HAVE BEEN CONSISTENTLY SUGGESTING THAT A SURFACE 
LOW WILL FORM ALONG THE MONSOON TROUGH NEAR 11N95W DURING 
THE PERIOD OF TODAY THROUGH FRI WITH CYCLONIC WINDS OF 20 TO 25 
KT GRADUALLY EXPANDING OUT TO ABOUT 180 NM ON FRI MIXING WITH 
LONG PERIOD CROSS EQUATORIAL SOUTHWESTERLY SWELL AT 15 TO 18 
SECONDS...THAT WILL PROPAGATE N TO ALONG 15N BETWEEN 88W AND 
100W. THIS LOW MAY EVENTUALLY INTENSIFY INTO A TROPICAL SYSTEM
AS IT TRACKS NW. WILL HAVE TO AWAIT FOR FUTURE MODEL GUIDANCE
TO SEE HOW THIS SCENARIO PLAYS OUT...AND MAKE ADJUSTMENTS TO
THE HIGH SEAS ACCORDINGLY.

$$
AGUIRRE