000
AXPZ20 KNHC 201540
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE OCT 20 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 
1500 UTC.

...SPECIAL FEATURE... 
TROPICAL STORM RICK AT 19.7W 111.1W AT 1500 UTC OCT OR 230 NM 
SSW OF S TIP OF BAJA CALIFORNIA MOVING N-NE OR 040 DEG AT 6 KT.  
ESTIMATED MINIMUM CENTRAL PRES 991 MB.  MAXIMUM SUSTAINED WIND 
DIMINISH TO 55 WITH GUSTS TO 65 KT.  SATELLITE IMAGERY SHOWED 
SIGNIFICANT WEAKENING OF RICK WITHIN LAST 24 HRS.  THIS TREND 
NOT EXPECTED TO CONTINUE AS 20 KT WIND SHEAR ALOFT SHOULD REMAIN 
STEADY HOLDING RICK AS A VERY STRONG TROPICAL STORM.  IN 
ADDITION...POTENTIAL FOR HEAVY RAINFALL OVER MOUNTAINOUS TERRAIN 
INCREASES THE THREAT OF COASTAL FLOODING IN MAINLAND MEXICO. 
ASSOCIATED NUMEROUS STRONG CONVECTION IN SQUALLS WITHIN 60 NM OF 
CENTER EXCEPT 180 NM NE QUADRANT.  SEE LATEST NHC FORECAST/ 
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP5/WTPZ25 KNHC FOR MORE 
DETAILS.

...TROPICAL WAVES...
NONE.

...ITCZ...
INTERTROPICAL CONVERGENCE ZONE ALONG LINE 09N83W TO 08N98W TO 
13N106W TO 14N115W TO 07N132W TO 08N140W.  SCATTERED MODERATE 
WITH ISOLATED STRONG CONVECTION WITHIN 90 NM S OF AXIS E OF 106W 
AND WITHIN 180 NM SE OF AXIS FROM 109W TO 117W.

OTHER SIGNIFICANT CONVECTION...
SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 60 NM EITHER 
SIDE OF A LINE FROM 07N84W TO 11N88W. THIS CONVECTION ORIGINATED 
ALONG THE COAST OF COSTA RICA AND NICARAGUA AND IS MOVING OUT 
FROM THE COAST. THE CONVECTION SHOULD WEAKEN DURING THE NEXT 
SEVERAL HOURS.

...DISCUSSION...
UPPER TROUGH AXIS ALONG LINE THROUGH 32N113W TO 23N127W TO 
21N140W.  HEALTHY SW JET CORE PROVIDING STRONG SHEAR OVER 
TROPICAL STORM RICK HELPING IN ITS WEAKENING.  TROUGH EXPECTED 
TO SHIFT NE HOLDING SHEAR AT PRESENT LEVEL HOLDING ANY 
SIGNIFICANT FURTHER WEAKENING OF RICK. 

MID-UPPER LEVEL RIDGE CENTERED AT 16N101W MAINTAINS ANTICYCLONIC 
FLOW ACROSS BASIN E OF 105W HELPING STEER TROPICAL STORM RICK 
OVER CENTRAL MEXICO. 

AT THE SURFACE...
HIGH PRES CENTER AT 32N137W HAS RIDGE EXTEND TO 20N120W SQUEEZE 
GRADIENT AGAINST CALIFORNIA COAST INCREASING N TO NW FRESH 
BREEZE N OF 28N E OF 120W.  FRESH TRADE WINDS W OF 125W FROM 
15N-24N AND NE SWELLS COVER LARGE AREA N OF 12N W OF 120W.  

STRONG COLD FRONT EXPECTED TO APPROACH AREA LATE IN FORECAST 
PERIOD BRINGING INCREASE IN STRONG SW BREEZE N OF 26N W OF 135W 
WITH BUILDING SEAS DUE TO LARGE LONG PERIOD NW SWELLS.  

GAP WINDS...
GALE WARNING CURRENTLY IN EFFECT FOR GULF OF TEHUANTEPEC 
EXPECTED TO EXPIRE WITHIN 6 HRS AS TIGHT PRES GRADIENT ACROSS SE 
MEXICO WEAKENS.  STRONG N BREEZE WOULD LINGER THROUGH 24 HRS 
LONGER.

$$
WALLY BARNES