000
AXPZ20 KNHC 212154
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SAT JUL 21 2012

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 
2130 UTC.

...TROPICAL WAVE...
A TROPICAL WAVE EXTENDS FROM 16N106W TO 1009 MB LOW PRES NEAR 
08N108W. THE WAVE REMAINS EMBEDDED WITHIN AN AREA OF DEEP LAYER 
MOISTURE AS DEPICTED ON THE MIMIC/TPW ANIMATION. MOST OF THE 
CONVECTIVE ACTIVITY ASSOCIATED WITH THIS FEATURE IS S OF 11N AND 
IS IN ASSOCIATION WITH THE LOW PRES. N OF 11N...ISOLATED 
MODERATE TO STRONG CONVECTION IS NOTED WITHIN 90 NM W AND 180 NM 
E OF THE WAVE AXIS. THE WAVE WILL CONTINUE TO MOVE W IN TANDEM 
WITH THE LOW PRES. GLOBAL MODELS ARE NOW SUGGESTING THE POTENTIAL
FOR ADDITIONAL DEVELOPMENT OF THIS LOW PRES AREA OVER THE NEXT 
48 HOURS AND FOCUS IS BEING SHIFTED ON THIS LOW. AN AREA OF 20 
TO 25 KT WINDS AND 8 TO 10 FT SEAS ARE INTRODUCED IN THE HIGH 
SEAS FORECAST IN THE 24 AND 48 HOUR PERIOD.   

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH AXIS EXTENDS FROM 10N85W TO A WEAK 1008 MB 
LOW PRES NEAR 08N92W TO 09N100W TO A 1008 MB LOW NEAR 08N108W TO 
11N116W TO 10N129W THEN ITCZ TO BEYOND 05N140W. SCATTERED 
MODERATE TO STRONG WITHIN 120 NM S OF THE MONSOON TROUGH BETWEEN 
90W AND 107W. SCATTERED MODERATE ISOLATED STRONG FROM 05N TO 09N 
BETWEEN 83W AND 93W. SCATTERED MODERATE FROM 07N TO 13N BETWEEN 
118W AND 125W.

...DISCUSSION...
1029 MB HIGH PRESSURE CENTERED N OF THE FORECAST AREA NEAR 
37N140W EXTENDS A RIDGE SE ACROSS THE NORTHERN WATERS THROUGH 
30N130W TO NEAR 18N115W. THE PRESSURE GRADIENT BETWEEN THIS 
FEATURE AND LOWER PRES ALONG THE MONSOON TROUGH AND IN THE 
VICINITY OF THE ITCZ IS MAINTAINING FRESH 20 KT WINDS FROM 10N 
TO 18N W OF 125W AS DEPICTED BY A PORTION OF A 1718 UTC ASCAT 
SCATTEROMETER PASS. THIS AREA OF TRADES WILL CONTINUE THROUGH 
THE FORECAST PERIOD. THE HIGH PRES IS FORECAST TO STRENGTHEN N 
OF THE AREA BY MON. AS A RESULT... SEAS GENERATED BY FRESH TO 
STRONG WINDS JUST OFF THE CALIFORNIA COAST WILL REACH THE NE 
WATERS. 

THE GFS HAS CONTINUES TO INDICATE ANOTHER AREA OF LOW PRESSURE 
FORMING WITHIN THE MONSOON TROUGH SUN NIGHT INTO MON. HOWEVER 
THE MODEL ITSELF IS NOW MORE IN LINE WITH THE ECMWF AND UKMET 
GLOBAL MODELS IN DEPICTING WEAK LOW PRES IN THE FORECAST. AS 
NOTED ABOVE EMPHASIS APPEARS TO BE SHIFTING TOWARD THE LOW PRES 
NEAR 08N108W. 

CROSS EQUATORIAL LONG PERIOD SW SWELLS OF 17-20 SECONDS ARE 
CURRENTLY IMPACTING THE COAST OF MEXICO...CENTRAL AMERICA AND 
BAJA CALIFORNIA...INCLUDING THE FAR S PORTION OF THE SEA OF 
CORTEZ. THE POTENTIAL FOR LARGE BREAKING WAVES AND DANGEROUS RIP 
CURRENTS WILL SLOWLY EBB THROUGH THE REMAINDER OF THE WEEKEND AS 
THE SWELL TRAIN SUBSIDES. 

FRESH GAP WINDS OF 20 KT CONTINUE ACROSS THE GULF OF PAPAGAYO. 
THE FORECAST CALLS FOR WINDS TO BECOME MORE DIURNALLY FORCED 
WITH 20 KT WINDS ONLY POSSIBLE DURING THE OVERNIGHT AND EARLY 
MORNING HOURS WITH THE AID OF THE DRAINAGE FLOW. 

FRESH GAP WINDS ARE FUNNELING INTO THE GULF OF TEHUANTEPEC THIS 
MORNING...LIKELY IN ASSOCIATION WITH A 1019 MB HIGH PRESSURE 
CENTERED OVER THE STATE OF VERACRUZ. EXPECT WINDS IN THE 20 TO 
25 KT RANGE TODAY AND SUN WITH WINDS DIMINISHING TO 20 KT OR 
LESS BY MON.  

$$
COBB