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Eastern Pacific Tropical Discussion

Active Tropical Systems Basin Outlooks Satellite
Eastern Pacific Basin Tropical Discussion
 
431 
AXPZ20 KNHC 200950
TWDEP 

TROPICAL WEATHER DISCUSSION                                      
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
1005 UTC SAT SEP 20 2014

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 
0945 UTC.

...SPECIAL FEATURES...
 
TROPICAL STORM POLO LOCATED NEAR 20.5N 108.6W OR ABOUT 185  
MILES S-SE OF THE SOUTHERN TIP OF BAJA CALIFORNIA PENINSULA AT 
AT 0900 UTC SEP 20. THE MINIMUM CENTRAL PRESSURE IS ESTIMATED AT 
997 MB. POLO IS MOVING NW OR 315 DEG AT 06 KT...AND IS EXPECTED 
TO TURN MORE W-NW IN RESPONSE TO A LOW LEVEL RIDGE. POLO WILL 
PASS S OF THE SOUTHERN TIP OF BAJA TONIGHT. MAXIMUM SUSTAINED 
WINDS ARE CURRENTLY ARE AT 45 KT WITH GUSTS TO 55 KT. 

STRONG NE WIND SHEAR IS EXPOSING THE CENTER TO THE E OF 
SCATTERED MODERATE ISOLATED STRONG CONVECTION THAT IS CURRENTLY 
OBSERVED WITHIN 180 NM OVER W SEMICIRCLE WITH SCATTERED MODERATE 
CONVECTION ALSO OBSERVED WITHIN 90 NM OF 17.5N110W. SCATTERED 
MODERATE ISOLATED STRONG CONVECTION IS ALSO OBSERVED OVER THE 
SOUTHERN GULF OF CALIFORNIA WITHIN 60 NM OF 25N108W. POLO IS 
EXPECTED TO PRODUCE RAINFALL AMOUNTS OF 1 TO 3 INCHES...WITH 
ISOLATED STORM TOTAL AMOUNTS OF 5 INCHES OVER EXTREME SOUTHERN 
BAJA CALIFORNIA OVER THE NEXT FEW DAYS. THESE RAINS COULD RESULT 
IN LIFE-THREATENING FLASH FLOODS AND MUD SLIDES.

SWELLS GENERATED BY POLO WILL AFFECT PORTIONS OF THE PACIFIC  
COAST OF MEXICO FROM 17-24N...INCLUDING BOTH MAINLAND MEXICO AND 
THE SOUTHERN BAJA CALIFORNIA PENINSULA OVER THE NEXT FEW DAYS. 
THESE SWELLS CAN CONTRIBUTE TO THE GENERATION OF LIFE 
THREATENING SURF AND RIP CURRENT CONDITIONS. SEE THE LATEST 
PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPEP2/WTPZ32 KNHC 
AND FORECAST ADVISORY UNDER HEADERS MIATCMEP2/WTPZ22 KNHC FOR 
ADDITIONAL DETAILS. 

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
           
THE MONSOON TROUGH EXTENDS W ACROSS PANAMA AND COSTA RICA 
BETWEEN 08-10N TO THE PACIFIC COAST OF COSTA RICA AT 08N83W... 
THEN TURNS NW TO 11N92W...THEN TURNS W-SW TO 09N123W WHERE 
SCATTEROMETER WINDS INDICATE A TRANSITION TO AN ITCZ WHICH TURNS 
NW TO BEYOND 13N140W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION IS OBSERVED WITHIN 120 NM EITHER SIDE OF A LINE FROM 
06N77W TO 09N86W TO 09N96W TO 09N113W. 

SCATTERED MODERATE ISOLATED STRONG CONVECTION IS ALSO OBSERVED  
OVER AND WITHIN 120 NM W OF THE COAST OF CENTRAL AMERICA AND 
MEXICO FROM 86-100W.

...DISCUSSION...                                                 
A 1017 MB HIGH PRESSURE IS CENTERED NEAR 29N135W WITH A RIDGE 
EXTENDING SE TO NEAR 16N122W. THE RIDGE IS MAINTAINING NE-E 10-
15 KT TRADES ACROSS THE TROPICS N OF THE MONSOON TROUGH AND TO 
THE W OF 120W. THE SURFACE HIGH IS FORECAST TO SHIFT SE TO NEAR 
28N133W ON TUE ALLOWING A COLD FRONT TO MOVE INTO THE FAR NW 
WATERS BEGINNING LATE SUN NIGHT. THE FRONT WILL BE INITIALLY BE 
ACCOMPANIED BY ONLY A SW-W-WNW 10 KT WIND SHIFT. THE WEAK FRONT 
WILL REACH FROM 32N134W TO TO 26N134W LATE TUE AND THEN IS 
EXPECTED TO DISSIPATE ALONG A LINE FROM 32N128W TO 26N135W LATE 
WED. BY THEN A SECONDARY NORTHWESTERLY 15 KT SURGE WILL PUSH NW 
SWELLS INTO THE AREA WHERE THEY WILL MIX WITH LONG PERIOD SE 
SWELL...RESULTING IN SEAS BUILDING 8-12 FT ACROSS THE WATERS NW 
OF THE DISSIPATING FRONT...WITH THE MAXIMUM SEAS ALONG 31N. THIS 
SECONDARY SURGE WILL REACH THE PACIFIC COAST OF THE BAJA 
PENINSULA LATE THU WITH NW FLOW INCREASING TO 20 KT AND SEAS 
BUILDING 7-9 FT IN MIXING NW AND SE SWELL.       

$$
NELSON