000 AXPZ20 KNHC 181005 RRA TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC THU JUL 18 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 0945 UTC. ...TROPICAL WAVES... A TROPICAL WAVE EXTENDS FROM 19N108W TO 10N110W. THE 0454 UTC ASCAT PASS DEPICTED THE NE TO SE WIND SHIFT ACROSS THE WAVE AXIS WITH WIND SPEEDS OF 10 KT OR LESS. THE WAVE COINCIDES WITH A BULGE OF MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE CONVECTION IS WITHIN 30 NM OF 14N109W. WIDELY SCATTERED SHOWERS AND TSTMS ARE W OF THE WAVE AXIS FROM 10N TO 15N BETWEEN 110W AND 121W. GLOBAL MODELS SUGGEST THAT THE WAVE WILL GRADUALLY LOSE ITS SURFACE IDENTITY AS IT TRACKS WESTWARD THROUGH THE NEXT COUPLE OF DAYS. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... MONSOON TROUGH AXIS EXTENDS FROM 09N84W TO 10N95W TO 13N109W WHERE IT ENDS. SCATTEROMETER DATA INDICATES THE ITCZ AXIS BEGINS AT 13N110W...AND CONTINUES TO 10N122W TO 12.5N138W...THEN RESUMES AT 10N138W TO BEYOND 09N140W. SCATTERED TO NUMEROUS STRONG CONVECTION EXISTS FROM 04N-09N E OF 79W. SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 120 NM S AND 90 NM N OF THE TROUGH AXIS BETWEEN 83W-88W. SCATTERED STRONG CONVECTION IS WITHIN 120 NM S OF TROUGH BETWEEN 105W AND 107W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 07N TO 12N BETWEEN 132W- 136W...AND WITHIN 120 NM S OF TROUGH AXIS BETWEEN 105W-107W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM S OF ITCZ AXIS BETWEEN 114W-117W. ...DISCUSSION... AN ANTICYCLONE LOCATED WEST OF AREA NEAR 12N145W EXTENDS A RIDGE NEWD TO 28N128W. A WEAK UPPER LOW IS AT 27N126W. A TROUGH AXIS EXTENDS FROM THE LOW SSW TO NEAR 12N128W. SATELLITE WATER VAPOR IMAGERY SHOWS ABUNDANT STRONG SUBSIDENCE INDUCING A DRY AND VERY STABLE ATMOSPHERIC ENVIRONMENT W OF A LINE FROM 32N119W TO 20N122W TO 14N140W. ACROSS THE WEST-CENTRAL WATERS TO ABOUT 23N129W. THE UPPER LOW WILL LIFT N AND AND BECOME DIFFUSE IN THE UPPER SW FLOW AHEAD OF A BROAD UPPER TROUGH NW OF THE DISCUSSION AREA. OVER THE FAR EASTERN PORTION OF THE AREA...A HIGHLY AMPLIFIED UPPER LEVEL RIDGE IS PRESENT OVER MUCH OF THE WESTERN U.S. AND STRETCHES SSW TO THE EASTERN PORTION OF THE DISCUSSION AREA N OF 20N AND E OF 120W...AND ALSO SEWD TO SE MEXICO. A WELL DEFINED DEEP LAYER LOW IS LOCATED OVER THE BORDER OF NEW MEXICO...AND FAR NW MEXICO. AN INVERTED MID TO UPPER LEVEL TROUGH EXTENDS FROM 18N116W TO 11N117W. ELY WINDS ALOFT DOMINATE MUCH OF THE AREA N OF 05N E AND E OF ABOUT 121W...AND ARE TRANSPORTING DEBRIS CLOUDINESS FROM CONVECTION ALONG AND NEAR THE MONSOON TROUGH W TO NEAR 123W FROM 08N-24N. A DIFFLUENT FLOW PATTERN TO THE SE OF THE RIDGE OVER MEXICO IS HELPING TO SUPPORT THE SCATTERED TO NUMEROUS STRONG CONVECTION PREVIOUSLY MENTIONED FROM 04N-09N E OF 70W AS WELL AS SCATTERED MODERATE TO ISOLATED STRONG CONVECTION ACROSS MUCH OF CENTRAL AMERICA. AT THE SURFACE...A RIDGE EXTENDS FROM A 1027 MB HIGH N OF THE AREA AT 36N136W SE TO 26N117W...WHILE A SURFACE TROUGH WITH GOOD TRACK HISTORY IS ALONG A POSITION FROM 15N135W TO 10138W. NE WINDS OF 20-25 KT ARE NOTED FROM 14N-18N BETWEEN 134W-140W WITH SEAS TO 8 FT. BY LATE TONIGHT...THE TROUGH WILL BE ALONG 15N140W TO 10N142W. WINDS ARE FORECAST TO DIMINISH TO 20 KT OR LESS FROM 15N-18N W OF 135W WITH SEAS TO 8 FT IN NE SWELL. BY EARLY FRI EVENING...THE TROUGH WILL HAVE MOVED ENOUGH TO THE W OF THE AREA WITH WINDS 20 KT OR LESS AND SEAS LESS THAN 8 FT TO BE FOUND OVER THE FAR WESTERN PORTION OF THE AREA CURRENTLY BEING AFFECTED BY THE TROUGH ASSOCIATED CONDITIONS. A SURGE OF TRADE WINDS OVER THE CARIBBEAN SEA WILL PUSH GAP WINDS TO 20 KT THROUGH THE GULF PAPAGAYO DURING THIS MORNING...AND AGAIN FRI MORNING. THIS ALONG WITH SOME ASSISTANCE FROM A TROPICAL WAVE MOVING INTO THE WESTERN CARIBBEAN AND SOUTHERN CENTRAL AMERICA SHOULD ALLOW FOR A WEAK SURFACE LOW PRES AREA TO FORM ALONG THE MONSOON TROUGH OFF THE COAST OF COSTA RICA OVER THE NEXT 48 HOURS. GLOBAL MODELS CARRY THE LOW WESTWARD...REACHING 95W BY SAT AND NEAR 99W BY SUN WITH AN EXPECTED CENTRAL PRESSURE AROUND 1009 MB. FOR NOW...THE MAIN IMPACT IS EXPECTED TO BE AN INCREASE IN SHOWER AND TSTM ACTIVITY OVER THE WATERS E OF 100W. LONG PERIOD CROSS EQUATORIAL SOUTHWESTERLY SWELLS RESULTING IN COMBINED SEAS TO 8 FT DOMINATE THE FORECAST WATERS S OF LINE FROM 00N95W TO 11N105W TO 05S120W TO 00N129W. A SET OF LONG PERIOD SW SWELLS...WAVE PERIOD OF 19 TO 21 SECONDS...IS PRESENTLY REACHING MOST OF THE MEXICAN COAST AND WILL AFFECT MOST OF THE COAST OF CENTRAL AMERICA THROUGH TODAY...BRINGING ROUGH SURF CONDITIONS AND DANGEROUS RIP CURRENTS TO THOSE COASTS INTO SAT. $$ AGUIRRE