000
AXPZ20 KNHC 201526
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI JUL 20 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1430 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH AXIS EXTENDS FROM 09N84W TO A 1008 MB LOW 
PRES NEAR 08N101W TO A SECOND 1008 MB LOW PRES NEAR 12N115W TO A 
THIRD 1008 MB LOW PRES NEAR 08N128W THEN ITCZ TO BEYOND 05N140W. 
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS NOTED FROM 
06N TO 10N BETWEEN 82W AND 89W. SIMILAR CONVECTION IS FROM 05N 
TO 10N BETWEEN 100W AND 106W. SCATTERED MODERATE CONVECTION IS  
FROM 10N TO 13N BETWEEN 114W AND 126W.

...DISCUSSION...
A 1034 MB SUBTROPICAL HIGH CENTERED WELL NW OF THE FORECAST AREA 
NEAR 41N158W WITH RIDGE EXTENDING SE TO NEAR 20N112W. THE 
PRESSURE GRADIENT BETWEEN THIS FEATURE AND LOWER PRES ALONG THE 
MONSOON TROUGH IS MAINTAINING FRESH 20 KT WINDS FROM 12N TO 14N 
BETWEEN 120W AND 125W...AND FROM 10N TO 12N BETWEEN 125W AND 
140W BASED ON THE MOST RECENT SCATTEROMETER PASSES. THIS AREA OF 
TRADES WILL SHIFT WESTWARD OVER THE NEXT 48 HOURS. EXPECT SEAS 
OF 8 TO 9 FT GENERATED BY THESE WINDS.

AS PREVIOUSLY MENTIONED...THERE ARE THREE WEAK LOW PRES SYSTEMS 
EMBEDDED IN THE MONSOON TROUGH. NONE OF THEM ARE SHOWING SIGN 
OF ORGANIZATION. THE EASTERNMOST IS THE ACTIVE ONE AND IS 
INTERACTING WITH A TROPICAL WAVE-LIKE. A SURFACE TROUGH IS 
ANALYZED ON THE 1200 UTC SURFACE MAP EXTENDING FROM 15N110W TO 
LOW CENTER NEAR 08N101W. SCATTERED MODERATE TO ISOLATED STRONG 
CONVECTION IS NOTED EITHER SIDE OF THE TROUGH AXIS FROM 08N TO 
15N BETWEEN 100W AND 103W. TROPICAL CYCLONE FORMATION IS NOT 
EXPECTED IN ASSOCIATION WITH EITHER OF THESE LOWS DURING THE 
NEXT 48 HOURS. BEYOND 48 HOURS...GLOBAL MODELS CONTINUE TO 
INDICATE A LOW PRESSURE CENTER FORMING WITHIN THE MONSOON TROUGH 
IN THE AREA BETWEEN 90W AND 95W LATE SUN AND MON. THIS LOW 
PRESSURE AREA COULD BE THE RESULT OF A TROPICAL WAVE...CURRENTLY 
OVER THE CENTRAL CARIBBEAN...INTERACTING WITH THE TOPOGRAPHY OF 
CENTRAL AMERICA AND THE MONSOON TROUGH. THE GFS CONTINUES TO BE 
THE MOST AGGRESSIVE IN DEVELOPING THIS LOW. 

CROSS EQUATORIAL LONG PERIOD SW SWELLS OF 16-18 SECONDS WILL 
SPREAD ACROSS THE FORECAST AREA AND WILL IMPACT THE COAST OF 
MEXICO...CENTRAL AMERICA AND BAJA CALIFORNIA THIS UPCOMING  
WEEKEND. THE POTENTIAL EXISTS FOR LARGE BREAKING WAVES AND 
DANGEROUS RIP CURRENTS ALONG THE COAST AS THE SWELL TRAIN SLOWLY 
SUBSIDES. 

GAP WINDS OF 20 KT...WITH PULSES TO 25 KT ARE EXPECTED TO 
CONTINUE OVER THE GULF OF PAPAGAYO AS FRESH TO STRONG TRADE WIND 
FLOW IN THE SW CARIBBEAN FUNNELS THROUGH THE GAP. THE WINDS WILL 
BE GREATEST DURING THE OVERNIGHT AND EARLY MORNING HOURS WITH 
THE ASSISTANCE OF THE NOCTURNAL DRAINAGE FLOW. NARROW LINES OF 
LOW LEVEL CLOUDS ARE NOTED GENERALLY ORIENTED PARALLEL TO THE 
NE WIND FLOW.

FRESH TO STRONG GAP WINDS WILL ALSO START THROUGH THE GULF OF 
TEHUANTEPEC THIS AFTERNOON...LIKELY IN ASSOCIATION WITH A 1020 
MB HIGH PRES CENTERED BETWEEN TAMPICO AND TUXPAN IN MEXICO. 
VISIBLE SATELLITE IMAGERY SHOWS A LINE OF SHOWERS WITH EMBEDDED 
TSTMS MOVING AWAY FROM THE GULF OF TEHUANTEPEC...AN INDICATION 
THAT WINDS ARE STARTING TO BLOW ACROSS THE AREA. IN ADDITION... 
IXTEPEC IN THE STATE OF OAXACA IS REPORTING GUSTY NLY WINDS OF 
20 KT. THIS GAP WIND EVENT WILL CONTINUE THROUGH THE NEXT 48 
HOURS. 

$$
GR