000 AXPZ20 KNHC 311513 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC FRI AUG 31 2007 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1515 UTC. ...SPECIAL FEATURES... TROPICAL STORM GIL CENTERED NEAR 19.1N 117.4W...OR 480 NM WSW OF THE SOUTHERN TIP OF BAJA CALIFORNIA...AT 31/1500 UTC MOVING W 9 KT. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000 MB. AFTER LOOKING ALMOST CONVECTION-LESS EARLIER THIS MORNING A BURST OF NUMEROUS MODERATE/SCATTERED STRONG CONVECTION HAS DEVELOPED WITHIN 90 NM TO THE W OF THE LOW-LEVEL CENTER. GIL IS OVER SUFFICIENTLY WARM SST'S AND OVERALL THE SHEAR IS EXPECTED TO DECREASE. HOWEVER...A LARGE SHIELD OF STRATOCUMULUS CLOUDS SURROUNDING GIL ARE LIKELY ALREADY BEING INGESTING INTO THE CIRCULATION. THIS STABLE AIR IS EXPECTED TO BE THE CULPRIT IN PREVENTING ANY SIGNIFICANT STRENGTHENING AS GIL MOVES FURTHER INTO THIS STABLE AIRMASS. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP5/WTPZ25 KNHC FOR MORE DETAILS. TROPICAL DEPRESSION ELEVEN-E HAS BEEN UPGRADED TO TROPICAL STORM HENRIETTE. AS OF 31/1500 UTC HENRIETTE WAS CENTERED NEAR 15.7N 100.1W...OR ABOUT 75 NM S OF ACAPULCO MEXICO...MOVING WNW AT 9 KT. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1001 MB. THIS TROPICAL CYCLONE CONTINUES TO PRODUCE A LARGE BLOB OF MODERATE TO STRONG CONVECTION MOSTLY IN THE NW SEMICIRCLE FROM 14N-18N BETWEEN 99W-104W. RADAR DATA FROM ACAPULCO SHOWS THE CENTER OF CIRCULATION FAIRLY WELL WITH SOME BANDS...CONTAINING HEAVY RAINFALL...ONSHORE. RAINFALL IS ONE OF THE BIG CONCERNS WITH ACCUMULATIONS OF 4 TO 8 INCHES ALONG THE SOUTH COAST OF MEXICO FROM GUERRERO TO JALISCO...WITH POSSIBLE ISOLATED MAXIMUM AMOUNTS OF 15 INCHES...ESPECIALLY OVER HIGH TERRAIN. LIFE-THREATENING FLASH FLOODS AND MUDSLIDES ARE POSSIBLE. STEADY INTENSIFICATION IS FORECAST AS THE CURRENT EASTERLY SHEAR IS EXPECTED TO LESSEN. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP1/WTPZ21 KNHC FOR MORE DETAILS. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 9N84W 14N97W 15N111W 13N122W 11N140W. SCATTERED MODERATE CONVECTION IS WITHIN 90 NM S OF AXIS BETWEEN 89W-92W AND IN THE GULF OF TEHUANTEPEC N OF 14N BETWEEN 94W-97W. ...DISCUSSION... E OF 120W... THE MAIN ISSUE IS THE DEVELOPMENT AND TRACK OF TROPICAL STORM HENRIETTE ALONG THE MEXICAN COAST. ANALYSIS FROM UW-CIMSS SHOWS THE DEPRESSION MOVING INTO AN AREA OF SLIGHTLY WEAKER SHEAR OVER THE NEXT COUPLE OF DAYS WHICH WOULD LIKELY AID IN INTENSIFICATION. FOR THAT REASON AND BECAUSE THE CENTER IS ANTICIPATED TO REMAIN OFFSHORE STEADY STRENGTHENING IS FORECAST. HEAVY RAINFALL IS A BIG CONCERN FOR A PORTION OF THE MEXICAN COAST. THE OTHER ISSUE IS TROPICAL STORM GIL. SEE SPECIAL FEATURES ABOVE FOR DETAILS. THE MODERATE TO STRONG SHEAR AFFECTING BOTH OF THESE SYSTEMS IS DUE TO NE/E FLOW ALOFT BETWEEN AN UPPER LOW OVER THE SW CARIBBEAN...AND BROAD UPPER RIDGING OVER NRN BAJA. ASIDE FROM HIGH WINDS AND ROUGH SEAS NEAR THE STORM...FRESH SWLY WINDS DIRECTLY S OF GIL AS FAR AS S AS 7N ARE NOTED ON A 13Z QSCAT PASS. ELSEWHERE S OF THE ITCZ...S TO SW CROSS-EQUATORIAL FLOW REMAINS LIGHT TO MODERATE. THIS CONTINUES TO BE ACCOMPANIED BY MODERATE SWELL OF UP TO 8 FT OUT OF THE SRN HEMISPHERE...MAINLY W OF 95W. W OF 120W... THE UPPER FLOW ACROSS THIS AREA IS SOMEWHAT CONFLUENT BETWEEN A WELL DEFINED UPPER RIDGE CENTERED OVER NRN BAJA AND AN UPPER LOW JUST N OF THE HAWAIIAN ISLANDS. THIS STABLE ENVIRONMENT IS SUPPRESSING ANY DEEP CLOUD FORMATION ESPECIALLY W OF 130W. EVEN THE ITCZ IS DEVOID OF CONVECTION. SOME OF THIS STABLE AIR IS AFFECTING TROPICAL STORM GIL...LOCATED JUST E OF THIS ZONE. AS GIL MOVES DEEPER INTO THIS STABLE AIRMASS FURTHER INTENSIFICATION IS LESS LIKELY. HOWEVER...WINDS ARE EXPECTED TO PICK UP IN THIS AREA LATER TODAY AND TONIGHT AS GIL APPROACHES 120W. MODERATE TO LARGE CROSS EQUATORIAL SWELL AND SLIGHTLY INCREASED SLY FLOW IS POSSIBLE S OF THE ITCZ AS WELL. $$ CANGIALOSI