000
AXPZ20 KNHC 152126
TWDEP 

TROPICAL WEATHER DISCUSSION                                      
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
2205 UTC WED MAY 15 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...SPECIAL FEATURES...

NEWLY UPGRADED TROPICAL STORM ALVIN CENTERED NEAR 8.7N 105.1W AT 
15/2100 UTC OR 665 MI SSW OF ACAPULCO MEXICO MOVING W-NW AT 11 
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB. MAXIMUM 
SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 40 KT. SEE LATEST 
NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP1/WTPZ21 
KNHC FOR MORE DETAILS. SCATTERED MODERATE TO STRONG CONVECTION 
IS WITHIN 240 NM IN THE E SEMICIRCLE AND 180 NM IN THE W 
SEMICIRCLE OF ALVIN. ALSO...SCATTERED MODERATE CONVECTION IS 
FROM 12N TO 14N BETWEEN 101W AND 107W. 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 AFTERNOON.

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

THE MONSOON TROUGH AXIS IS FROM 07N78W TO 1009 MB LOW PRES NEAR 
06N79W TO 08N87W TO 07N100W WHERE IT ENDS...THEN RESUMES W OF 
TROPICAL STORM ALVIN FROM 08N108W TO 09N120W. THE ITCZ AXIS IS 
FROM 09N120W TO 07N130W TO 08N140W. SCATTERED MODERATE 
CONVECTION IS WITHIN 60 NM N OF THE MONSOON TROUGH BETWEEN 117W 
AND 120W...AND ALSO WITHIN 150 NM N OF THE ITCZ W OF 133W.

...DISCUSSION...

ALOFT...MOSTLY DRY AIR ALOFT IS PRESENT THROUGHOUT THE 
AREA...WITH THE EXCEPTION OF S OF ABOUT 18N WHERE UPPER LEVEL 
MOISTURE FROM THE DEEP TROPICAL PACIFIC IS STREAMING EWD ACROSS 
THE AREA.

AT THE SURFACE...HIGH PRES IS PRESENT N OF ABOUT 12N AND W OF 
115W. ELSEWHERE A WEAK PRES PATTERN REMAINS IN PLACE. THE 
EARLIER OBSERVED TIGHT PRES GRADIENT JUST INLAND THE GULF OF 
TEHUANTEPEC IS RELAXING AS NOW TROPICAL STORM ALVIN CONTINUES TO 
MOVE FURTHER TO THE W-SW OF THE TEHUANTEPEC REGION.

NE-E WINDS OF 20-25 KT ACCOMPANIED BY 8 FT SEAS THROUGH THE GULF 
OF PAPAGAYO ARE FORECAST TO PULSE TONIGHT INTO EARLY THU... 
DIMINISHING TO 20 KT OR LESS BY THU AFTERNOON.
 
NW-N WINDS OF 20-25 KT THROUGH THE GULF OF PANAMA...AND S TO 
NEAR 06N CONTINUE. WEAK 1009 MB LOW PRES HAS DEVELOPED JUST S OF 
THE GULF OF PANAMA NEAR 06N79W...WITH SCATTERED MODERATE TO 
STRONG CONVECTION N OF THE MONSOON TROUGH E OF 83W...AND WITHIN 
180 NM S OF THE MONSOON TROUGH E OF 86W. THE GFS SOLUTION IS THE 
STRONGEST AS FAR AS DEVELOPING/DEEPENING THIS LOW. THE LOW IS 
FORECAST TO GRADUALLY DRIFT NW OF THE AREA BY LATE THU NIGHT.

WAVEWATCH GUIDANCE AND EC WAVE GUIDANCE HAS BACKED OFF ON 
SENDING 8 FT OR GREATER NW SWELL...GENERATED BY NORTHERLY WINDS 
OFF OF THE CALIFORNIA COAST...INTO THE FAR NE PORTION OF THE 
DISCUSSION AREA W OF NORTHERN BAJA CALIFORNIA LATE TONIGHT WITH 
ONLY THE UKMET WAVE GUIDANCE STILL SHOWING 8-9 FT SEAS. 

LONG PERIOD SW SWELL IS EXPECTED TO PROPAGATE INTO THE FAR W 
CENTRAL WATERS FROM 14N TO 20N W OF 136W BY FRI MORNING INTO 
AFTERNOON.

$$
LEWITSKY