000
AXPZ20 KNHC 161603
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI OCT 16 2009

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1545 UTC.

...SPECIAL FEATURE... 

WHAT WAS TROPICAL STORM RICK JUST A SHORT WHILE AGO HAS BEEN 
UPGRADED TO A HURRICANE AT 1500 UTC CENTERED NEAR 12.7N 99.4W AT 
1500 UTC OR ABOUT 290 NM...470 KM S OF ACAPULCO MEXICO MOVING 
WNW AT 8 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 987 MB. 
MAXIMUM SUSTAINED WINDS HAVE INCREASED TO 65 KT WITH GUSTS TO 80 
KT. SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS 
MIATCMEP5/WTPZ25 KNHC FOR MORE DETAILS. THE OVERALL STRUCTURE OF 
THE CYCLONE HAS BECOME VERY SYMMETRICAL AND QUITE LARGE WITH 
VERY IMPRESSIVE BANDING FEATURES NOTED IN ADDITION TO WHAT 
APPEARS TO BE A CDO (CENTRAL DENSE OVERCAST) OVER THE CENTER.
THE BANDS CONSISTS OF NUMEROUS MODERATE TO STRONG CONVECTION
WITHIN 60 NM EITHER SIDE OF A LINE FROM 14N96W TO 15N100W TO
12N102W TO 10N98W. THE CDO CONSISTS OF NUMEROUS MODERATE 
TO STRONG WITHIN 45 NM OF 12N99W. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION WITHIN 30 NM EITHER SIDE OF THE LINE FROM 
10N94W TO 13N95W TO 14N96W MAKE UP THE REMAINDER OF THE BANDING
FEATURE NOTED. 20 TO 33 KT WINDS EXTEND OUTWARD UP TO 300 NM FROM
THE CENTER IN THE NE SEMICIRCLE AND WITHIN 240 NM IN THE SE 
SEMICIRCLE OF RICK. ATMOSPHERIC CONDITIONS APPEAR FAVORABLE FOR
RICK TO CONTINUE TO UNDERGO INTENSIFICATION UNDER A LOW SHEAR
ENVIRONMENT THROUGH THE NEXT 48 HOURS AS IT TRACKS WNW.

...ITCZ...

THE AXIS OF THE INTERTROPICAL CONVERGENCE ZONE IS CENTERED ALONG 
7N77W TO 11N90W TO 8N100W TO 9N111W TO 12N115W TO 12N140W. 
SCATTERED MODERATE/ISOLATED STRONG CONVECTION EXISTS FROM 7N-11N 
E OF 94W...AND WITHIN 60 NM OF THE LINE 11N107W TO 5N117W...AND 
ALSO WITHIN OF THE LINE FROM 13N119W TO 10N127W AND FROM 5N-0N 
BETWEEN 130W-140W.

...DISCUSSION...

W OF 120W...
A DEEP LAYER RIDGE WITH A MEAN CENTER NEAR 16N135W DOMINATES
THIS PORTION OF THE AREA WITH A SURFACE 1020 MB HIGH NEAR
31N29W. A LARGE DEEP LAYER TROUGH IS JUST NW OF THE AREA MOVING 
E WITH ITS ASSOCIATED SURFACE COLD FRONT WITHIN ABOUT 120 NM WNW 
OF 30N140W. THE TROUGH IS FORECAST TO BROADEN AND SLOWLY LIFT NE 
THROUGH THE NEXT 24-48 HOURS AS THE COLD FRONT BECOMES 
STATIONARY AND WEAKENED ALONG A LINE FROM 30N137W TO 27N140W. 
SEAS OF 9-11 FT IN NW SWELLS WILL FOLLOW IN THE WAKE OF THE 
FRONT. THE FRONT WILL DISSIPATE LATE SAT AFTERNOON INTO SAT 
EVENING AS SEAS SUBSIDE TO LESS THAN 8 FT. TO THE S OF THE RIDGE 
CENTER...A 1009 MB LOW IS ALONG THE ITCZ NEAR 12N136W. THE PRES 
GRADIENT BETWEEN THE LOW AND WEAK SURFACE RIDGING TO ITS N IS 
RESULTING IN WINDS OF 20-25 KT WITHIN 300 NM IN THE NE 
SEMICIRCLE WITH SEAS IN THE RANGE OF 8-11 FT. THE LOW...MOVING W 
10-15 KT...IS FORECAST TO MOVE W OF THE AREA IN 24 HOURS AS THE 
SURFACE RIDGE ALSO SHIFTS W OVER THE NEXT FEW DAYS.

E OF 120W...

A MID/UPPER LEVEL TROUGH EXTENDS FROM ALONG THE WRN U.S. 
SOUTHWARD INTO THE AREA ROUGHLY ALONG 119W. A SMALL UPPER LEVEL 
CYCLONIC CIRCULATION MOVING W 15 KT IS ON THE TROUGH NEAR 19N. A 
MID/UPPER LEVEL ANTICYCLONIC CIRCULATION IS OVER WRN MEXICO NEAR 
21N103W WITH A RIDGE EXTENDING NW TO WELL N OF THE AREA ACROSS 
THE WRN U.S. TO THE SW OF THE ANTICYCLONE...THE UPPER FLOW 
PATTERN BECOMES DIFFLUENT AIDING ITCZ CONVECTION BETWEEN ABOUT 
103W-109W. AN INVERTED MID/UPPER LEVEL TROUGH IS W OF THE 
DIFFLUENT ZONE ALONG 16N110W TO 12N114W TO 8N117W. A SURFACE 
TROUGH MOVING W ABOUT 10 KT IS ALONG 113W FROM 6N TO 14N. 
MAJORITY OF RELATED CONVECTION IS ALONG THE ITCZ...WITH ONLY 
ISOLATED WEAK SHOWERS AND TSTMS WITHIN 120 NM EITHER SIDE OF THE 
TROUGH FROM 12N TO 14N. TO THE E OF THE AREA OF HIGH PRES 
MENTIONED ABOVE N-NE WINDS OF 20 KT ARE OCCURRING N OF 27N E OF 
125W TO THE W OF COAST OF THE BAJA CALIFORNIA PENINSULA DUE TO A 
TIGHT PRES GRADIENT BETWEEN N TO S TROUGHING ACROSS THE GULF OF 
CALIFORNIA AND THE SURFACE RIDGE. THESE WINDS ARE FORECAST TO 
MERGE WITH WIND CONDITIONS RELATED TO THE OUTER FRINGES OF 20-33 
KT WINDS ASSOCIATED WITH HURRICANE RICK.

A DEEP LAYER MID LATITUDE TROUGH WILL AMPLIFY OVER THE GULF OF 
MEXICO SAT AND SEND A STRONG COLD FRONT THROUGH THE BAY OF 
CAMPECHE. THE NORTHERLY FLOW SHOULD FUNNEL THROUGH THE ISTHMUS 
OF TEHUANTEPEC BY SAT EVENING...WITH N TO NE WINDS INCREASING 
TO 20-25 KT...AND TO 20-30 KT BY SUN WITHIN 120 NM EITHER SIDE
OF A LINE FROM 16N95W TO 12N99W. SEAS THERE ARE FORECAST TO 
BUILD UP TO 10 FT.

$$
AGUIRRE