000 AXPZ20 KNHC 010939 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC THU AUG 01 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 0930 UTC. ...SPECIAL FEATURES... HURRICANE GIL AT 14.3N 122.8W AT 01/0900 UTC MOVING W-NW OR 285 DEG AT 10 KT. MAXIMUM SUSTAINED WINDS ARE 70 KT WITH GUSTS TO 85 KT AND ESTIMATED MINIMUM SEAS PRESSURE IS 990 MB. CURRENTLY NUMEROUS STRONG CONVECTION IS OBSERVED WITHIN 90 NM NW AND WITHIN 30 NM SE SEMICIRCLES OF CENTER. SCATTERED MODERATE ISOLATED STRONG NOTED ELSEWHERE IN A BAND WITHIN 210 NM OF CENTER FROM THE S QUADRANT TO NW QUADRANT. GIL IS EXPECTED TO MOVE WESTWARD FOR THE NEXT 3 DAYS ALONG THE SOUTHERN PERIPHERY OF A LARGE UPPER LEVEL ANTICYCLONE WHICH WILL PROVIDE CONTINUED FAVORABLE CONDITIONS FOR ADDITIONAL STRENGTHENING FOR ANOTHER DAY OR SO. SEE LATEST NHC FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP2/WTNT22 KNHC FOR ADDITIONAL DETAILS. A 1008 MB LOW PRESSURE IS CENTERED NEAR 12.5N114.5W AND IS MOVING W AT 11 KT. CURRENTLY A BAND OF SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED WITHIN 90 NM OVER THE E SEMICIRCLE OF CENTER. THIS LOW MAY DEVELOP INTO A TROPICAL CYCLONE AS IT MOVES W-NW TO NEAR 13N117W LATE TONIGHT...AND NEAR 14N120W ON FRI NIGHT ACCOMPANIED BY CYCLONIC WINDS OF 20-25 KT AND SEAS 7-10 FT WITHIN 75 NM OF THE CENTER. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS W ALONG 10N FROM THE NW COAST OF COLOMBIA AT 10N75W TO THE PACIFIC COAST OF COSTA RICA AT 10N85W...TO 09N93W LOW PRESSURE AT 12.5N114.5W...THEN W TO NEAR 14N120W WHERE IT LOSES IDENTITY IN THE BROAD CYCLONIC CIRCULATION ASSOCIATED WITH TROPICAL CYCLONE GIL. SCATTEROMETER DATA INDICATES THAT A SURFACE LOW ANALYZED YESTERDAY HAS WEAKEND TO A TROUGH ORIENTATED N TO S FROM 11N130W TO 15N129W...AND IS ACCOMPANIED BY SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN 45 NM EITHER SIDE OF A LINE FROM 15N130W TO 13N127W. SCATTEROMETER WINDS INDICATED THE INTERTROPICAL CONVERGENCE ZONE FORMS W OF THE THIS TROUGH NEAR 12N131W AND CONTINUES SW TO BEYOND 10N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED WITHIN 60 NM EITHER SIDE OF A LINE FROM 05N77W TO 08N79W TO 09N85W...IN CLUSTERS WITHIN 90 NM OF 08N90W AND 08N99W...AND WITHIN 90 NM EITHER SIDE OF A LINE FROM 13N98W TO 09N109W TO 13N120W. ...DISCUSSION... UPPER CYCLONES CENTERED AT 31N143W AND 26N139W ARE EMBEDDED WITHIN AN UPPER TROUGH WITH MEAN AXIS ALONG 32N131W TO 17N140W. 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 TROPICAL PACIFIC AT 14N140W. 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 24N BETWEEN 103- 122W. UPPER DEBRIS MOISTURE...FROM PREVIOUS CONVECTION ALONG THE NORTHERN SIERRA MADRE OCCIDENTAL...OVER NW OLD MEXICO...AND SCATTERED MODERATE CONVECTION CURRENTLY OVER THE SOUTHERN GULF OF CALIFORNIA...IS ADVECTED W ACROSS THE BAJA PENINSULA TO NEAR 27N118W BEFORE COMPLETELY EVAPORATING. DENSE UPPER MOISTURE IS ALSO ADVECTED N...AND LATER E WITHIN THE UPPER RIDGE ACROSS MOST OF ARIZONA AND NEW MEXICO...ACROSS NORTHERN TEXAS WHERE INTENSE CONVECTION IS OCCURRING. A SMALL UPPER CYCLONE IS EMBEDDED WITH THE UPPER ANTICYCLONIC FLOW NEAR 23N117W...AND CONTINUES TO MOVE W WITHIN THE UPPER EASTERLY FLOW WHILE TROPICAL CYCLONE GIL LOCATED FURTHER TO THE S PROGRESSES W ALONG THE SOUTHERN EXTENT OF THE UPPER ANTICYCLONIC FLOW. ANOTHER UPPER CYCLONE IS OVER THE COAST OF OLD MEXICO AT 10N105W...WITH UPPER DIFFLUENCE OVER ITS SEMICIRCLE SUPPORTING CONVECTION OVER INTERIOR MEXICO NEAR 18N91W. AN UPPER ANTICYCLONE IS CENTERED NEAR 17N112W WITH A RIDGE EXTENDING E TO A CREST AT 15N97W. THE ENVELOPE OF ANTICYCLONIC FLOW IS ENHANCING CONVECTION PREVIOUSLY DESCRIBED ALONG AND TO THE S OF THE EASTERN PORTION OF THE MONSOON TROUGH. INTENSE CONVECTION ACCOMPANIED BY FREQUENT LIGHTNING...HAS DEVELOPED AGAIN THIS MORNING ALONG WESTERN COLOMBIA AND ACROSS THE GULF OF PANAMA AS PREVIOUSLY DESCRIBED. ANOTHER STRONG CLUSTER OF CONVECTION HAS FORMED ALONG THE MONSOON TROUGH AND IS MOVING W ACROSS THE N COAST OF COSTA RICA AND SE NICARAGUA AT THE MOMENT. A SURFACE RIDGE EXTENDS FROM 32N137W TO 20N107W. NE TRADES AT 15- 20 KT ARE ENHANCED SW OF THE RIDGE...FROM 12-20N TO THE W OF 130W. MIXING NE AND SE SWELL RESULT IN COMBINED SEAS OF 6-9 FT. THE AFFECTED AREA IS FORECAST TO SHRINK W TONIGHT THROUGH FRI...THEN INCREASE AGAIN AS TROPICAL CYCLONE GILL PASSES THROUGH THE AREA THIS WEEKEND. $$ NELSON