000
AXPZ20 KNHC 180914
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SUN OCT 18 2009

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

...SPECIAL FEATURE... 

EXTREMELY DANGEROUS CATEGORY FIVE HURRICANE RICK WAS CENTERED 
NEAR 15.3N 107.2W AT 0900 UTC OR ABOUT 450 NM...890 KM SSE OF 
CABO SAN LUCAS MEXICO MOVING WNW AT 12 KT. ESTIMATED MINIMUM 
CENTRAL PRESSURE IS 906 MB. MAXIMUM SUSTAINED WINDS 155 KT WITH 
GUSTS TO 190 KT...MAKING RICK THE SECOND MOST POWERFUL HURRICANE 
ON RECORD IN THE EAST PACIFIC AFTER HURRICANE LINDA OF 1997. 
RICK CONTINUES TO MAINTAIN ITS STRENGTH WITH A WELL DEFINED EYE 
SURROUNDED BY A 105 NM WIDE RING OF VERY COLD TOP CONVECTION. 
THE EYE DIAMETER IS ESTIMATED TO BE 22 NM. NUMEROUS STRONG 
CONVECTION IS WITHIN 150 NM OF CENTER. SCATTERED MODERATE WITH 
ISOLATED STRONG CONVECTION IS ELSEWHERE WITHIN 240 NM OF CENTER. 
RICK IS A LARGE HURRICANE WITH AN AREA OF 20 TO 33 KT WINDS 
FOUND UP TO 360 NM IN THE E AND 210 NM IN THE W SEMICIRCLES WITH 
SEAS TO 50 FT NEAR THE CORE OF THE STORM. ATMOSPHERIC CONDITIONS 
ARE FAVORABLE FOR THE CYCLONE TO CONTINUE WITH RATHER LOW 
VERTICAL WIND SHEAR ENVIRONMENT ALONG WITH VERY CONDUCIVE SEA 
SURFACE TEMPERATURES THROUGH THE NEXT 12-24 HOURS AS IT TRACKS 
WNW. SEE THE LATEST NHC FORECAST ADVISORY UNDER AWIPS/WMO 
HEADERS MIATCMEP5/WTPZ25 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 120W FROM 07N TO 17N MOVING W AT ABOUT 
13 KT. ONLY ISOLATED MODERATE CONVECTION IS NEAR THE WAVE AXIS 
MAINLY OVER THE SOUTHERN PORTION WITHIN THE ITCZ.

...ITCZ...

THE AXIS OF THE INTERTROPICAL CONVERGENCE ZONE IS CENTERED ALONG 
06N77W TO 10N110W TO 09N120W TO 14N130W TO 10N140W. SCATTERED 
MODERATE WITH ISOLATED STRONG CONVECTION IS WITHIN THE AREA FROM 
08.5N TO 11N FROM 107W TO 114W. SCATTERED MODERATE TO STRONG 
CONVECTION IS WITHIN 75 NM OF THE POINT 13.5N133W.

...DISCUSSION...

DEEP LAYER TROUGH IS OVER THE NORTHWEST PART OF THE AREA. NW OF 
A LINE THROUGH 32N127W TO 22N140W. THE AREA IS DRY AND CLOUD 
FREE IN THE MIDDLE AND UPPER LEVELS WITH BROKEN STRATOCUMULUS 
BECOMING SCATTERED BEYOND 120 NM NW OF THE ABOVE LINE. SOUTHERLY 
FLOW AHEAD OF THE TROUGH AXIS IS BRINGING A PLUME OF MIDDLE AND 
UPPER LEVEL MOISTURE NORTHEASTWARD WITHIN 400 NM SOUTHEAST OF 
THE TROUGH AXIS MAINLY NORTH OF 25N. ONLY BROKEN HIGH CLOUDS ARE 
OBSERVED IN THIS FLOW.

NARROW UPPER TROUGH IS ALONG A LINE FROM CENTRAL BAJA CALIFORNIA 
TO 17N125W TO 11N140W. EXCEPT FOR THE MOISTURE DESCRIBED ABOVE 
THE AREA NORTHWEST OF THIS TROUGH IS DRY AND CLOUD FREE IN THE 
MIDDLE AND UPPER LEVELS. WITH MOSTLY OVERCAST STRATOCUMULUS IN 
THE LOWER LEVELS NORTH OF 19N.  

LARGE OVERALL ANTICYCLONIC OUTFLOW CENTERED OVER HURRICANE RICK 
EXTENDS OUT ABOUT 500 NM FROM THE CENTER HOWEVER THE INNER 120 
NM RADIUS CORE SHOWS CYCLONIC TURNING.

ANOTHER TROUGH EXTENDS FROM EASTERN MEXICO AND NORTHERN CENTRAL 
AMERICA TO OVER THE PACIFIC NORTH OF THE ITCZ FROM ABOUT 87W TO 
96W. SUBSIDENCE PREVAILS IN THIS AREA HOWEVER SOME ISOLATED 
CONVECTION IS OCCURRING.

REMAINDER OF THE MIDDLE AND UPPER LEVELS IS A BROAD 
ANTICYCLONIC FLOW.

WEAKENING COLD FRONT IS ALONG THE LINE THROUGH 32N131W TO 
28N140W. OTHERWISE WEAK SURFACE RIDGE IS NORTH OF 18N WEST OF 
120W. ELSEWHERE EXCEPT FOR THE TROPICAL CYCLONE A BROAD TROUGH 
IS ANALYZED AT THE SURFACE.

GAP WINDS...
THE SOUTHERN EXTENT OF A SHARP UPPER LEVEL TROUGH IS NE OF THE 
AREA OVER THE GULF OF MEXICO...AND HAS PUSHED A STRONG COLD 
FRONT PAST THE BAY OF CAMPECHE. STRONG HIGH PRES IN ITS WAKE IS 
USHERING IN NORTHERLY WINDS THROUGH THE ISTHMUS OF TEHUANTEPEC 
WITH N TO NE WINDS OF GALE FORCE OCCURRING. WINDS ARE EXPECTED 
TO FURTHER INCREASE TO STORM FORCE 45-50 KT BY SUN EVENING. GALE 
FORCE WINDS ARE EXPECTED TO PERSIST THROUGH 48 HOURS. 

$$
LL