000 AXPZ20 KNHC 311538 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC WED JUL 31 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 1545 UTC. ...SPECIAL FEATURES... TROPICAL STORM GIL NEAR 13.6N 119.9W AT 31/1500 UTC MOVING W-NW OR 285 DEG AT 12 KT. MAXIMUM SUSTAINED WINDS ARE 50 KT WITH GUSTS TO 60 KT. A RECENT SCATTEROMETER PASS INDICATING THAT THE RADIUS OF 34 KT WINDS IS EXPANDING OR THE N SEMICIRCLE. CURRENTLY NUMEROUS STRONG CONVECTION IS OBSERVED IN BANDS WITHIN 60 NM OF THE CENTER WITH SCATTERED MODERATE ISOLATED STRONG CONVECTION NOTED ELSEWHERE WITHIN 90 NM OF THE CENTER. GIL IS EXPECTED TO MOVE WESTWARD FOR THE NEXT FEW DAYS ALONG THE SOUTHERN PERIPHERY OF A LARGE UPPER LEVEL ANTICYCLONE WHICH WILL PROVIDE FAVORABLE CONDITIONS FOR INTENSIFICATION. THIS TRACK IS ALSO ACROSS WARM SEAS SURFACE TEMPERATURES SO GIL IS FORECAST TO BECOME A MINIMAL HURRICANE WITHIN THE NEXT 48 HOURS. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP2/WTNT22 KNHC FOR ADDITIONAL DETAILS. A 1009 MB LOW PRESSURE IS CENTERED NEAR 12N112W AND IS MOVING W AT 15 KT. OVER THE PAST 6 HOURS THERE HAS BEEN LITTLE IN THE WAY OF CIONVECTION NOTED WITH THIS LOW. HOWEVER...AN AREA OF SCATTERED MODERATE CONVECTION IS NOTED WITHIN 45 NM OF THE LOW LEVEL CENTER IN THE NW QUADRANT. THIS LOW HAS A MODERATE CHANCE OF DEVELOPING INTO A TROPICAL CYCLONE OVER THE NEXT 48 HOURS AS IT MOVES WNW TO NEAR 13N115W THU ..AND NEAR 13N118W ON FRI. WINDS ACCOMPANTING THE LOW WILL BE KEPT AT 20-25 KT AND SEAS 8-11 FT WITHIN ABOUT 120 NM N AND 60 NM S SEMICIRCLES OF THE CENTER THROUGH 48 HOURS. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... MONSOON TROUGH AXIS EXTENDS FROM THE COAST OF COSTA RICA NEAR 10N86W TO 09N96W TO A 1009 MB LOW PRES NEAR 12N112W. THE ITCZ AXIS EXTENDS FROM W OF T.S. GIL NEAR 12N127W TO 10N140W. SCATTERED MODERATE TO STRONG CONVECTION WAS NOTED N OF 06N E OF 88W TO THE COAST OF PANAMA AND COSTA RICA. SCATTERED MODERATE ISOLATED STRONG WITHIN 120 NM EITHER SIDE OF AXIS BETWEEN 94W AND 110W. ...DISCUSSION... THE MEAN AXIS OF AN UPPER TROUGH EXTENDS FROM 32N132W THROUGH UPPER CYCLONES NEAR 27N138W AND 21N135W...THEN CONTINUES SW TO BEYOND 15N140W. A LARGE UPPER ANTICYCLONE HAS BEEN QUASI- STATIONARY OVER THE TEXAS PANHANDLE FOR THE PAST FEW DAYS WITH AN UPPER RIDGE CURRENTLY EXTENDING SW ACROSS THE CENTRAL BAJA CALIFORNIA PENINSULA TO A SHARP CREST OVER THE DEEP TROPICAL PACIFIC AT 14N132W. DRY UPPER AIR IS INDICATED TO THE W OF THIS RIDGE AND EXTENDS W THROUGH THE UPPER TROUGH. THE ENVELOPE OF ANTICYCLONIC FLOW EXTENDS S OVER THE DISCUSSION AREA TO THE N OF 22N BETWEEN 105-121W. UPPER DEBRIS MOISTURE...FROM PREVIOUS CONVECTION ALONG THE NORTHERN SIERRA MADRE OCCIDENTAL AND OVER NW OLD MEXICO...IS ADVECTED W ACROSS THE GULF OF CALIFORNIA AND THE BAJA PENINSULA ROUGHLY TO THE N OF 26N AND REACHES NEAR 26N120W BEFORE EVAPORATING. SOME OF THIS UPPER MOISTURE IS ALSO ADVECTED N...AND LATER NE WITHIN THE UPPER RIDGE...THEN E ACROSS SOUTHERN ARIZONA...NEW MEXICO AND TEXAS. A SMALL UPPER CYCLONE IS EMBEDDED WITH THE UPPER ANTICYCLONIC FLOW NEAR 20N118W...AND CONTINUES TO MOVE W WITHIN THE UPPER LEVEL EASTERLY FLOW WHILE TROPICAL CYCLONE GIL LOCATED FURTHER TO THE S PROGRESSES W ALONG THE SOUTHERN EXTENT OF THE UPPER ANTICYCLONIC FLOW. AN UPPER ANTICYCLONE IS CENTERED NEAR 15N107W AND ANOTHER IS CENTERED OVER GUATEMALA WITH THEIR COMBINED ENVELOPE OF ANTICYCLONIC FLOW EXTENDING S OVER THE TROPICS TO THE N OF 04N BETWEEN 83-114W. THE ASSOCIATED UPPER DIFFLUENCE IS SUPPORTING THE CONVECTION PREVIOUSLY DESCRIBED ALONG AND TO THE S OF THE EASTERN PORTION OF THE MONSOON TROUGH. INTENSE CONVECTION HAS DEVELOPED AGAIN THIS MORNING ALONG WESTERN COLOMBIA AND ACROSS THE GULF OF PANAMA AS PREVIOUSLY DESCRIBED. ANOTHER STRONG CLUSTER HAS FORMED ALONG THE MONSOON TROUGH AND IS MOVING W ACROSS THE COASTS RICA AND NICARAGUA BORDER AT THE MOMENT. A SURFACE RIDGE EXTENDS FROM 32N140W TO 18N110W. NE TRADES AT 15- 20 KT ARE ENHANCED SW OF THE RIDGE FROM 12-18N TO THE W OF 130W. MIXING NE AND SE SWELL RESULT IN COMBINED SEAS OF 6-8 FT. THESE CONDITIONS ARE FORECAST TO REMAIN IN PLACE ACROSS THE TROPICAL WATERS OVER THE HEXT 36 TO 48 HOURS. THE AREA WILL GRADUALLY SUBSIDE IN ADVANCE OF TROPICAL CYCLONE GIL ON FRI. $$ COBB