000
AXPZ20 KNHC 160250
TWDEP 

TROPICAL WEATHER DISCUSSION                                      
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
0405 UTC THU MAY 16 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0300 UTC.

...SPECIAL FEATURES...

TROPICAL STORM ALVIN CENTERED NEAR 9.0N 105.9W AT 16/0300 UTC OR 
ABOUT 700 MI S OF MANZANILLO MEXICO MOVING W-NW AT 10 KT. 
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1004 MB. MAXIMUM SUSTAINED 
WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. SEE LATEST NHC 
FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP1/WTPZ21 KNHC 
FOR MORE DETAILS. SCATTERED MODERATE TO STRONG CONVECTION IS 
WITHIN 60 NM OF THE CENTER. SCATTERED MODERATE CONVECTION IS 
ELSEWHERE WITHIN 300 NM IN THE NE SEMICIRCLE AND 180 NM IN THE 
SW QUADRANT OF ALVIN. ALVIN IS ON THE SW PERIPHERY OF A MID-
LEVEL RIDGE AND THIS FEATURE SHOULD CONTINUE TO STEER THE STORM 
W-NW FOR THE NEXT FEW DAYS. ALVIN IS FORECAST TO BECOME A 
HURRICANE BY FRI MORNING.

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

THE MONSOON TROUGH AXIS EXTENDS FROM 07N77W TO LOW PRES NEAR 
06N79W 1007 MB TO 09N86W TO 08N101W THEN RESUMES FROM 08N109W TO 
08N120W. THE ITCZ AXIS FROM 08N120W TO 07N140W. SCATTERED 
MODERATE AND ISOLATED STRONG CONVECTION IS FROM 04N TO 08N 
BETWEEN 82W AND 87W...WITHIN 60 NM EITHER SIDE OF THE MONSOON 
TROUGH BETWEEN 110W AND 120W...AND ALSO WITHIN 180 NM N OF 
THE ITCZ W OF 127W.

...DISCUSSION...

ALOFT...MOSTLY DRY AIR ALOFT IS PRESENT N OF A LINE FROM 23N107W 
TO 17N140W...WITH UPPER LEVEL MOISTURE FROM THE DEEP TROPICAL 
PACIFIC STREAMING EASTWARD ACROSS THE REMAINDER OF AREA S OF THE 
SAME LINE AND W OF 110W...AND ADVECTING WESTWARD E OF 110W.

AT THE SURFACE...HIGH PRES IS PRESENT N OF ABOUT 12N AND W OF 
115W. ELSEWHERE A WEAK PRES PATTERN REMAINS IN PLACE.

NE-E WINDS OF 20-25 KT ACCOMPANIED BY 8 FT SEAS WILL PULSATE 
AGAIN LATER TONIGHT IN THE GULF OF PAPAGAYO THROUGH THU 
MORNING...DIMINISHING TO 20 KT OR LESS BY THU AFTERNOON.
 
WEAK 1007 MB LOW PRES IS JUST S OF THE GULF OF PANAMA NEAR 
06N79W. FRESH TO STRONG WINDS ARE PRESET WITHIN 120 NM OF THE 
LOW CENTER IN THE S SEMICIRCLE. THE LOW WILL MOVE TO 07N79W BY 
THU MORNING...TO 08N79W FRI MORNING...THEN MOVING N OF THE AREA 
BY FRI AFTERNOON WITH WINDS DIMINISHING TO 20 KT OR LESS AND 
SEAS SUBSIDING TO LESS THAN 8 FT BY FRI AFTERNOON.

LONG PERIOD SW SWELL IS EXPECTED TO PROPAGATE INTO THE FAR W 
CENTRAL WATERS FROM 14N TO 20N W OF 136W BY FRI MORNING... 
LINGERING INTO FRI NIGHT OVER THE SAME GENERAL AREA.

$$
LEWITSKY