000
AXPZ20 KNHC 200906
TWDEP 

TROPICAL WEATHER DISCUSSION                                      
NWS NATIONAL HURRICANE CENTER MIAMI FL                        
1005 UTC SAT APR 20 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0730 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...              
THE MONSOON TROUGH WAS ANALYZED FROM 09N78W TO 10N86W TO 07N97W 
TO 08N105W TO 07N109W. THE ITCZ AXIS WAS ANALYZED FROM 07N109W 
TO 04N119W TO 06N130W TO 05N140W. SCATTERED MODERATE CONVECTION 
WAS WITHIN 90 NM N OF THE AXIS BETWEEN 108W AND 112W AND S OF 
THE AXIS TO 03N BETWEEN 108W AND 114W. SCATTERED MODERATE TO 
STRONG CONVECTION WAS WITHIN 60 NM N OF THE AXIS W OF 130W AND 
WITHIN 120 NM S OF THE AXIS BETWEEN 132W AND 136W.

...DISCUSSION...                                                
GULF OF TEHUANTEPEC...THE 0354 UTC ASCAT PASS SHOWED GALE FORCE 
N WINDS HAVE MOVED INTO THE GULF OF TEHUANTEPEC BEHIND A COLD 
FRONT THAT MADE ITS WAY THROUGH THE SW GULF OF MEXICO FRI 
EVENING. GALE CONDITIONS ARE EXPECTED TO BE BRIEF...DIMINISHING 
BY SAT AFTERNOON AS THE DRIVING HIGH PRESSURE BEHIND THE FRONT 
QUICKLY SHIFTS NORTHEASTWARD AWAY FROM THE SW GULF. WINDS WILL 
DIP BELOW ADVISORY CONDITIONS OVERNIGHT SAT NIGHT. NE SWELL FROM 
TEHUANTEPEC WILL MERGE WITH CROSS-EQUATORIAL 16-18 SECOND PERIOD 
SW SWELL BY SUN...WITH SEAS SUBSIDING TO 8 FT OVERNIGHT SUN 
NIGHT.

GULF OF CALIFORNIA...THE 0358 UTC ASCAT PASS SHOWED FRESH TO 
STRONG NW WINDS CONTINUE IN THE CENTRAL GULF OF CALIFORNIA FOR 
NOW. WINDS ARE EXPECTED TO DIMINISH AROUND SUNRISE AS THE 
PRESSURE GRADIENT OVER NW MEXICO SLACKENS. 

ALOFT...A VAST ANTICYCLONE CENTERED NEAR 15N107W EXTENDS A RIDGE 
AXIS NORTHWESTWARD TO 32N128W AS WELL AS EASTWARD ALONG THE 
SOUTHERN MEXICAN BORDER INTO THE NW CARIBBEAN. SCATTERED 
MODERATE TO STRONG CONVECTION FOUND WITHIN 90 NM OF THE COAST OF 
AND EL SALVADOR BETWEEN 90W-93W AND WITHIN 60 NM OF THE NW COAST 
OF NICARAGUA FROM 12N-13N IS BEING ENHANCED BY THE UPPER LEVEL 
DIFFLUENCE ASSOCIATED WITH THE RIDGE AXIS. THE ANTICYCLONE IS 
EXPECTED TO WEAKEN OVER THE NEXT TWO DAYS AS THE WESTERN RIDGE 
AXIS EDGES ITS WAY EASTWARD TO THE BAJA CALIFORNIA PENINSULA. 
THIS WILL MAKE ROOM FOR THE UPPER LOW THAT IS CURRENTLY NEAR 
28N143W TO MAKE ITS WAY OVER NW WATERS...REACHING NEAR 33N137W 
BY THE END OF THE FORECAST PERIOD EARLY MON MORNING. DRY AIR AND 
IMPLIED SUBSIDENCE DOMINATE MUCH OF THE REGION N OF 10N...EXCEPT 
WHERE SOUTHERLY FLOW IS TRANSPORTING TROPICAL MOISTURE ALOFT 
BETWEEN 120W-130W. THIS MOISTURE IS PRIMARILY MANIFESTED AS 
PATCHY CIRRUS.

AT THE SURFACE...THE 1034 MB SUBTROPICAL HIGH LIES NEAR 38N138W 
AND EXTENDS A RIDGE AXIS SOUTHEASTWARD TO 12N105W. MODERATE TO 
FRESH NE TRADE WINDS LIE BETWEEN THE RIDGE AXIS AND THE ITCZ 
OVER WESTERN WATERS. WINDS HERE ARE EXPECTED TO DIMINISH TO A 
GENTLE TO MODERATE BREEZE BY SUN NIGHT...WITH SEAS THAT ARE 
CURRENTLY AROUND 9 FT UNDER NE SWELL GRADUALLY SUBSIDING BELOW 8 
FT. 

$$
SCHAUER