000
AXPZ20 KNHC 131532
TWDEP 

TROPICAL WEATHER DISCUSSION                                   
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
1605 UTC SAT APR 13 2013

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1300 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...              
THE MONSOON TROUGH AXIS WAS ANALYZED FROM 08N77W TO 07N86W TO 
05N90W TO 05N100W TO 04N107W. THE ITCZ AXIS WAS ANALYZED FROM 
04N107W TO 03N112W TO 06N119W TO 05N123W TO 03N140W. SCATTERED 
MODERATE WITH ISOLATED STRONG CONVECTION WAS S OF THE AXIS TO 
03N BETWEEN 84W AND 88W. SCATTERED MODERATE CONVECTION WAS 
WITHIN 30 NM N AND 120 NM S OF THE AXIS BETWEEN 91W AND 94W. 
SCATTERED MODERATE CONVECTION WAS BETWEEN 60 NM AND 180 NM S OF 
THE AXIS BETWEEN 97W AND 100W. A TROUGH LIES JUST N OF THE AXIS 
FROM 10N116W TO 05N120W. SCATTERED MODERATE CONVECTION WAS 
WITHIN 60 NM NW OF THE TROUGH N OF 08N. 

...DISCUSSION...                                                
A RIDGE ALOFT EXTENDS FROM AN ANTICYCLONE N OF THE AREA NEAR 
34N137W THROUGH 20N125W TO A SECOND ANTICYCLONE NEAR 10N98W AND 
THROUGH COSTA RICA TO A THIRD ANTICYCLONE ALONG THE CARIBBEAN 
COAST OF COLOMBIA NEAR 09N77W. DIFFLUENCE ALONG THIS UPPER RIDGE 
AXIS IS ENHANCING THE VERTICAL MOTION NEAR 10N110W WHERE A POOL 
OF 2.0-2.5 INCH PRECIPITABLE WATER VALUES LIES. SCATTERED 
MODERATE TO STRONG CONVECTION IS EVIDENT ON INFRARED IMAGERY AND 
IN LIGHTNING DATA FROM 08N TO 12N BETWEEN 106W AND 112W. UPPER 
DIFFLUENCE BETWEEN THE TWO EASTERN ANTICYCLONES AND A WEAK UPPER 
LOW NEAR 00N91W IS ALSO ENHANCING LIFT NEAR AN AREA OF POOLED 
LOW- TO MID-LEVEL MOISTURE ALONG THE ITCZ OVER WATERS BETWEEN 
84W AND 88W. CONVECTION HERE IS DESCRIBED IN THE SECTION ABOVE.  
ELSEWHERE...AN UPPER TROUGH LIES FROM NORTHEASTERN NEW MEXICO 
THROUGH SONORA AND THE CENTRAL BAJA CALIFORNIA PENINSULA TO 
24N116W. WATER VAPOR IMAGERY SHOWS DRY AIR ALOFT IN THE VICINITY 
OF THE TROUGH. THIS TROUGH WILL KICK EASTWARD SUN...BUT A MEAN 
TROUGH WILL LINGER OVER THE SW U.S. AND NW MEXICO AS A NEW 
TROUGH AXIS MOVES IN TO REPLACE IT. 

THE 1028 MB SUBTROPICAL SURFACE HIGH LIES NEAR 37N141W AND 
EXTENDS A RIDGE SOUTHEASTWARD THROUGH 20N120W TO 15N104W. 
MODERATE TO FRESH NE TRADE WINDS LIE W OF THE RIDGE AXIS AND A 
SMALL AREA OF 8 FT SEAS LIES FROM 17N-22N W OF 136W. THESE SEAS 
ARE EXPECTED TO SUBSIDE OVER THE NEXT 24 HOURS. TO THE NE OF THE 
RIDGE AXIS LIES A BROAD AREA OF FRESH TO STRONG N-NW WINDS OFF 
THE COAST OF SOUTHERN CALIFORNIA N OF THE FORECAST AREA AS SEEN 
BY THE 0444 UTC ASCAT PASS. N SWELL IS PROPAGATING FROM THIS 
REGION INTO NE FORECAST WATERS...WITH SEAS IN THE 8 TO 10 FT 
RANGE FOUND N OF 24N BETWEEN 115W-132W. THE SUBTROPICAL HIGH IS 
FORECAST TO MIGRATE NORTHWARD THROUGH THE WEEKEND. IT WILL BE 
IMPINGED UPON BY A COLD FRONT TO ITS N BY LATE SUN...WITH HIGH 
PRESSURE REORGANIZING N OF THE FRONT BY MON. TRADES WILL 
GRADUALLY WEAKEN AS THE HIGH MOVES FARTHER AWAY FROM THE AREA 
BUT THE PRESSURE GRADIENT BETWEEN THE HIGH AND THE LOWER PRES 
OVER THE INTERMOUNTAIN WESTERN U.S WILL KEEP WINDS STRONG ALONG 
THE CALIFORNIA COAST...AND NORTHERLY SWELL WILL CONTINUE TO 
PROPAGATE INTO NE FORECAST WATERS THROUGH MON.

CROSS-EQUATORIAL SWELL WITH PERIODS IN EXCESS OF 20 SECONDS ON 
ITS LEADING EDGE IS MAKING ITS WAY NORTHWARD THROUGH OFFSHORE 
PACIFIC WATERS S OF 15N TODAY. SEAS ARE BUILDING OVER WATERS S 
OF 03N AND E OF 113W THIS MORNING...WITH SEAS TO 9 FEET EXPECTED 
TO BRIEFLY OVERTAKE THE AREA S OF 10N W OF THE GALAPAGOS TO 110W 
AND S OF 06N E OF THE GALAPAGOS TO 81W ON SUN BEFORE SUBSIDING. 
THE LEADING EDGE OF THE SWELL WILL MAKE ITS WAY TO THE ENTIRE 
CENTRAL AMERICAN AND MAINLAND MEXICAN COAST TONIGHT AND THE BAJA 
CALIFORNIA PENINSULA ON SUN.

$$
SCHAUER