East Pacific Tropical Weather Discussion

000
AXPZ20 KNHC 132147
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SAT OCT 13 2012

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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...SPECIAL FEATURE...

SATELLITE IMAGES INDICATE THAT THE LOW PRESSURE SYSTEM THAT WAS 
LOCATED ALONG THE MONSOON TROUGH ABOUT SEVERAL HUNDRED MILES 
SOUTH-SOUTHWEST OF THE SOUTHERN TIP OF BAJA CALIFORNIA HAS 
ACQUIRED A WELL-DEFINED CENTER AND SUFFICIENT CONVECTIVE 
ORGANIZATION TO BE CLASSIFIED AS A TROPICAL CYCLONE...NAMED 
PAUL. AT 13/2100 UTC...PAUL IS CENTERED NEAR 14.0N 113.6W MOVING 
WEST OR 270 DEGREES AT 13 KT. A TURN TO THE NORTHWEST WITH A 
DECREASE IN FORWARD SPEED IS EXPECTED ON SUNDAY...FOLLOWED BY A 
NORTHWARD MOTION BY MONDAY. THE OFFICIAL NHC TRACK FORECAST 
BRINGS PAUL NEAR THE BAJA CALIFORNIA PENINSULA IN ABOUT 4 TO 5 
DAYS. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB. MAXIMUM 
SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. PAUL IS 
FORECAST TO SLOWLY STRENGTHEN DURING THE NEXT 48 HOURS... 
REACHING HURRICANE STATUS BY MON. AFTER 48 HOURS...THE SHEAR IS 
EXPECTED TO INCREASE AND WATERS COOL TO MARGINAL LEVELS ALONG 
THE EXPECTED TRACK. THESE FACTORS SHOULD INDUCE A WEAKENING AS 
PAUL APPROACHES TO THE BAJA CALIFORNIA PENINSULA. NUMEROUS 
STRONG CONVECTION IS NOTED WITHIN 120 NM W AND 60 NM E 
SEMICIRCLES. NUMEROUS MODERATE CONVECTION IS ELSEWHERE FROM 12N 
TO 17N BETWEEN 112W AND 116W. SEE LATEST NHC FORECAST/ADVISORY 
UNDER AWIPS/WMO HEADERS MIATCMEP1/WTPZ21 KNHC FOR MORE DETAILS.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

MONSOON TROUGH EXTENDS FROM 09N84W TO 1010 MB LOW PRES NEAR 
06N93W TO 08N97W THEN RESUMES W OF T.S. PAUL FROM 12N116W TO 
11N130W TO 07N140W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION IS WITHIN 120 NM W SEMICIRCLE OF LOW PRES NEAR 
06N93W. SCATTERED MODERATE CONVECTION CAN BE FOUND FROM 12N TO 
14N BETWEEN 122W AND 126W. SIMILAR CONVECTION IS FROM 06N TO 08N 
BETWEEN 127W AND 134W.

...DISCUSSION...

AN UPPER LEVEL SHORT WAVE TROUGH EXTENDS FROM SOUTHERN 
CALIFORNIA TO 23N128W...DRIFTING SE WHERE IT IS EXPECTED TO 
CUT-OFF AND STALL NEAR 25N120W BY EARLY SUN AS A MID TO UPPER 
LEVEL RIDGE BUILDS ALONG 135W N OF 25N. THE SHORT WAVE TROUGH IS 
PROVIDING SUPPORT TO A WEAKENING FRONTAL BOUNDARY THAT EXTENDS 
FROM 30N132W TO 26N140W. THE FRONT IS FORECAST TO DISSIPATED ON 
SUN AS THE UPPER SUPPORT SHIFTS EAST. 

A TIGHT PRES GRADIENT BETWEEN THE 1026 MB HIGH PRES NEAR 35N125W 
AND LOW PRES OVER NW MEXICO IS RESULTING IN FRESH NLY FLOW OFF 
THE COAST OF NORTHERN BAJA...AS NOTED IN LATEST SCATTEROMETER 
PASSES...AND FEW SHIP OBSERVATIONS. SIMILARLY FRESH TO LOCALLY 
STRONG NW FLOW WILL PERSIST IN THE CENTRAL PORTION OF THE GULF 
OF CALIFORNIA THROUGH TONIGHT...BEFORE DIMINISHING OVERNIGHT. 
THE HIGH PRES WILL MERGE WITH HIGH PRES BEHIND THE DYING FRONT 
AND REORGANIZE NEAR 31N130W BY SUN AFTERNOON. 

SCATTEROMETER DATA PROVIDED OBSERVATIONS OF FRESH TO STRONG 
TRADE WINDS BETWEEN THE SUBTROPICAL RIDGE AND T.S. PAUL COVERING 
THE REGION FROM 11N TO 16N W OF 125W. MEANWHILE RESIDUAL NW 
SWELL ALONG WITH FRESH NE TRADES WILL MAINTAIN COMBINED SEAS 8 
TO 10 FT. THE AERIAL EXTENT OF THE TRADES IS EXPECTED TO 
DECREASE THROUGH 48 HOURS WITH SEAS SUBSIDING TO 8 FT IN MIXED 
NW AND NE SWELL. 

PERSISTENT STRONG HIGH PRES OVER THE GULF OF MEXICO CONTINUES TO 
ALLOW FRESH TO STRONG GAP WIND FLOW TO PULSE THROUGH THE GULF OF 
TEHUANTEPEC...PRIMARILY DURING OVERNIGHT AND EARLY MORNING HOURS.

$$
GR