000
AXPZ20 KNHC 211600
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC WED OCT 21 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 INLAND AT 23.4N 106.3W AT 1500 UTC OCT 21 OR 
15 MILES N-NE OF MAZATLAN MEXICO. RICK IS MOVING NE OR 050 DEG 
AT 15 KT. ESTIMATED MINIMUM CENTRAL PRES IS 990 MB. MAXIMUM 
SUSTAINED WINDS ARE 45 KT GUSTS 55 KT. RICK WILL CONTINUE TO 
WEAKEN AS IT MOVES FARTHER INLAND OVER THE MOUNTAINOUS TERRAIN 
OF CENTRAL MEXICO. STILL SOME LINGERING SCATTERED MODERATE 
CONVECTION ASSOCIATED WITH AN OUTER BAND WITHIN 45 NM OF THE 
COAST ALTHOUGH ANY REMAINING CONVECTION WILL CONTINUE TO 
DISSIPATE AND PUSH INLAND OVER THE NEXT FEW HOURS. THE MAIN 
CONCERN AND AFFECT OF RICK WILL BE HEAVY RAINFALL OVER MEXICO 
WHICH MAY PRODUCE LIFE THREATENING FLASH FLOODS AND MUD SLIDES. 
SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS 
MIATCMEP5/WTPZ25 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

NONE.

...ITCZ...

INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...08N82W TO 
09N100W TO 13N106W TO 14N115W TO 06N140W. SCATTERED MODERATE AND 
ISOLATED STRONG CONVECTION IS WITHIN 180 NM OF EITHER SIDE OF THE
AXIS FROM 82W TO 90W. SCATTERED MODERATE AND ISOLATED STRONG 
CONVECTION IS WITHIN 150 NM OF EITHER SIDE OF THE AXIS FROM 122W 
TO 140W.

...DISCUSSION...

AN UPPER LEVEL TROUGH EXTENDS OVER THE NE PACIFIC FROM 20N105W 
TO 10N130W. THIS TROUGH EXTENDS INLAND INTO N MEXICO AND WILL 
CONTINUE TO STEER RICK TO THE NE FARTHER INLAND. 

AT THE SURFACE...A RIDGE OF HIGH PRESSURE IS OVER THE NE PACIFIC 
N OF 15N WITH DRY AND STABLE AIR IN PLACE. ANOTHER UPPER LEVEL 
TROUGH IS JUST TO THE N OF THE AREA WITH AN ASSOCIATED SURFACE 
COLD FRONT WHICH WILL GENERATE BUILDING SEAS AND EVENTUALLY 
PROPAGATE INTO OUR NW AREA LATE IN THE FORECAST PERIOD. IN 
ADDITION A TIGHTENING PRESSURE GRADIENT BETWEEN THE HIGH AND THE 
LOW PRESSURE OF THE ITCZ WILL GENERATE FRESH TRADES AT THE 
SURFACE.

A WEAK AREA OF LOW PRES EMBEDDED IN THE ITCZ IS STATIONARY 
NEAR THE COAST OF COSTA RICA. THIS LOW WILL REMAIN STATIONARY.

GAP WINDS...
IN THE GULF OF TEHUANTEPEC WILL CONTINUE TO DIMINISH TO LESS 
THAN 20 KNOTS BY LATE THIS AFTERNOON.

$$
LEWITSKY