000
AXPZ20 KNHC 171524
TWDEP 

TROPICAL WEATHER DISCUSSION                                    
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
1605 UTC WED JUL 17 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 
1500 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS CURRENTLY ANALYZED ALONG 105W/106W N OF THE 
MONSOON TROUGH...AND PRESENTS WELL IN GOES DERIVED HIGH DENSITY 
WIND DATA. CONVECTION REMAINS FAIRLY LIMITED CURRENTLY...BUT 
WILL LIKELY FLARE LATER THIS EVENING AS THE TROPICAL WAVE 
BRIEFLY INTERACTS WITH THE DISSIPATING UPPER LOW. GLOBAL MODELS 
ARE IN FAIR AGREEMENT INDICATING THE WAVE WILL DAMPEN OUT AS IT 
TRACKS FARTHER WEST THROUGH THE NEXT COUPLE OF DAYS.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...   
     
THE MONSOON TROUGH AXIS EXTENDS FROM 08N78W TO LOW PRES NEAR 
13N106W 1008 MB TO LOW PRES NEAR 10N115W 1008 MB TO 10N120W. THE 
ITCZ EXTENDS FROM 10N120W TO 13N130W...THEN CONTINUES FROM 
09N137W TO 09N140W. NUMEROUS MODERATE TO SCATTERED STRONG 
CONVECTION NOTED WITHIN 240 NM S OF THE MONSOON TROUGH AXIS E OF 
82W. SCATTERED MODERATE CONVECTION WITHIN 90 NM S OF MONSOON 
TROUGH AXIS BETWEEN 88W AND 92W...WITHIN 120 NM S OF MONSOON 
TROUGH AXIS BETWEEN 100W AND 105W...WITHIN 180 NM EITHER SIDE OF 
MONSOON TROUGH AXIS BETWEEN 111W AND 119W. SCATTERED MODERATE 
ISOLATED STRONG CONVECTION WITHIN 60 NM EITHER SIDE OF ITCZ AXIS 
BETWEEN 128W AND 130W.

...DISCUSSION... 

AN UPPER TROUGH EXTENDS FROM AN UPPER LOW CENTERED NEAR 23N125W 
TO 13N130W. THE TERMINUS OF THE UPPER TROUGH IS JUST TO THE EAST 
OF AN TROPICAL UPPER RIDGE CENTERED W OF THE AREA NEAR 12N145W. 
DIVERGENCE ALOFT RELATED TO THE INTERSECTION OF THE UPPER TROUGH 
AND THE UPPER RIDGE OVER THE ITCZ IS SUPPORTING CLUSTERS OF 
CONVECTION W OF 125W AND A SURFACE TROUGH EXTENDING FROM 14N131W 
TO 08N136W...PARTIALLY DEFINED IN AN ASCAT PASS FROM 07 UTC. 
UPPER LOW AND TROUGH WILL LARGELY LOSE DEFINITION AND DAMPEN OUT 
OVER THE NEXT 24 HOURS AHEAD OF AN AMPLIFYING UPPER TROUGH ALONG 
145W NE OF HAWAII. THIS WILL ENHANCE THE SURFACE TROUGH AS IT 
SLIPS W OF THE AREA THROUGH THU MORNING. THE MAIN MARINE IMPACT 
WILL BE THE BRIEF POTENTIAL FOR NE WINDS OF 20 TO 25 KT AHEAD OF 
THE SURFACE TROUGH LATE TODAY...WITH SEAS TO 8 FT. THE 07 UTC 
ASCAT PASS INDICATED WINDS TO 20 KT AT THAT TIME...WITH AN 
ACCOMPANYING ALTIMETER PASS SHOWING SEAS ALREADY CLOSE TO 8 FT. 
THE HIGHER WINDS AND SEAS WILL SHIFT W OF 140W ALONG WITH THE 
TROUGH THU. WEAK TO MODERATE CONVECTION WILL PERSIST ALONG THE 
ITCZ W OF 130W INTO FRI DUE TO MODERATE TO FRESH TRADE WIND 
CONVERGENCE. 

A SURFACE LOW IS ANALYZED ALONG THE MONSOON TROUGH NEAR 
09N116W...ON THE SOUTHEAST SIDE OF THE UPPER LOW. AREAS OF 
CONVECTION ARE NOTED WITHIN 180 NM ON EITHER SIDE OF THE MONSOON 
TROUGH AXIS...ENHANCED BY DIVERGENCE ALOFT RELATED TO THE UPPER 
LOW. THIS FEATURE WILL BECOME LESS DISTINCT THROUGH LATE THU AS 
THE SUPPORTING UPPER LOW WEAKENS AND AS A MORE VIGOROUS 
TROPICAL WAVE MOVES INTO THE AREA FROM THE EAST...AS DESCRIBED 
IN THE TROPICAL WAVE SECTION ALOFT. 

A SURGE OF TRADE WINDS OVER THE CARIBBEAN WILL PUSH GAP WINDS TO 
20 KT TONIGHT AND LATE FRI THROUGH THE GULF PAPAGAYO. THIS ALONG 
WITH SOME ASSISTANCE FROM A TROPICAL WAVE MOVING INTO THE 
WESTERN CARIBBEAN AND SOUTHERN CENTRAL AMERICA OVER THE NEXT 48 
HOURS WILL ALLOW A WEAK SURFACE LOW PRES AREA TO FROM ALONG THE 
MONSOON TROUGH OFF THE COAST OF COSTA RICA THROUGH FRI. GLOBAL 
MODELS CARRY THE LOW WESTWARD...REACHING 95W BY EARLY SAT WITH A 
EXPECTED MSLP AROUND 1009 MB. THE MAIN IMPACT WILL BE INCREASED 
SHOWERS AND THUNDERSTORMS OVER THE WATERS E OF 100W...MAINLY 
ALONG THE COASTLINES DURING THE LATE NIGHT AND EARLY MORNING 
HOURS. 

AN UPPER LOW ANOMALOUSLY MOVING WESTWARD FROM THE SOUTHERN 
PLAINS INTO THE NEW MEXICO THIS MORNING IS EXPECTED TO 
EVENTUALLY PUSH SW INTO THE GULF OF CALIFORNIA FRI INTO SAT. 
THIS WILL ENHANCE SURFACE TROUGHING OVER THE GULF AND BAJA...AND 
ITS INTERACTION WITH RIDGING TO THE WEST TO ALLOW FRESH NW WINDS 
OFF THE NORTHERN COAST OF BAJA BY LATE THU...WITH SEAS BUILDING 
TO 8 FT. THE UPPER LOW WILL WEAKEN FRI AND SAT ALLOWING WINDS AND 
SEAS TO DIMINISH.

A CRYOSAT ALTIMETER PASS FROM AROUND 08 UTC INDICATED SEAS TO 8 
FT CLOSE TO THE EQUATOR NEAR 115W. THIS IS RELATED TO SW SWELL 
MOVING OUT OF THE SOUTHERN HEMISPHERE...REACHING AS FAR N AS 03N 
BETWEEN 110W AND 120W. WW3 AND ECWAVE GUIDANCE INDICATES THIS 
WILL DECAY TO LESS THAN 8 FT BY EARLY FRI.
  
$$ 
CHRISTENSEN