000 AXPZ20 KNHC 072203 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC THU AUG 07 2008 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2145 UTC. ...SPECIAL FEATURE... TROPICAL STORM HERNAN IS CENTERED NEAR 14.8N 116.7W OR ABOUT 715 NM...1050 KM SOUTHWEST OF THE SOUTHERN TIP OF BAJA CALIFORNIA AT 07/2100 UTC MOVING WNW AT 12 KT. MAXIMUM SUSTAINED WIND SPEED IS 55 KT WITH GUSTS TO 65 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 992 MB. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS. THE CYCLONE HAS CONTINUED TO BECOME BETTER DEFINED DURING THE DAY AS OBSERVED ON VISIBLE SATELLITE IMAGERY. THIS IS APPARENT BY ITS WELL-DEFINED BANDING FEATURES AND VERY PRONOUNCED BURSTS OF DEEP CONVECTION OVER AND WITHIN ALL QUADRANTS OF THE CENTER. THIS CONVECTION CONSISTS OF NUMEROUS STRONG WITHIN 60 NM S OF OF THE CENTER. SCATTERED STRONG CONVECTION IS ELSEWHERE WITHIN 90 NM NW AND N QUADRANTS...AND 60 NM OF THE CENTER IN THE NE QUADRANT. AN OUTER BAND CONSISTING OF SCATTERED/MODERATE ISOLATED STRONG CONVECTION IS IDENTIFIED FROM 10N-12N BETWEEN 118W-124W...AND ALSO FROM 12N-14N BETWEEN 116W-119W. LATEST VISIBLE IMAGERY SHOWS WHAT APPEARS TO BE A DEVELOPING EYE FEATURE SIGNIFYING POSSIBLE STRENGTHENING WITH HERNAN. A QUIKSCAT PASS FROM 1322 UTC THIS MORNING SHOWED THE CENTER OF HERNAN BEING LOCATED OVER THE NE PART OF THE CONVECTION WITH 20 KT WINDS EXTENDING AS FAR S AS 8N...AND AS FAR N AS 18N. WATER VAPOR SATELLITE-DERIVED WINDS ARE STRONGEST OVER THE W SEMICIRCLE OF HERMAN AS IT MOVES AROUND THE SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE. HERMAN IS FORECAST TO STRENGTHEN INTO A HURRICANE LATE TONIGHT...AND GRADUALLY CONTINUE TO STRENGTHEN THROUGH SAT AFTERNOON...BEFORE MOVING ENCOUNTERING COOLER WATER AND WEAKENING. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 104W FROM 7N TO 16N MOVING W ABOUT 12 KT. THIS WAVE WAS RE-POSITIONED SLIGHTLY W BASED VISIBLE SATELLITE AVAILABLE DURING THE AFTERNOON. SCATTERED MODERATE ISOLATED/STRONG CONVECTION IS AHEAD OF THE WAVE FROM 10N-14N BETWEEN 107W-109W. SIMILAR CONVECTION IS WITHIN 30 NM OF 13.5N106W. A WEAK MID-LEVEL CIRCULATION IS WITHIN 120 NM W OF THE WAVE MORE TIED TO THE ITCZ NEAR 10N104W. THIS WAVE REMAINS UNDER A VERY FAST UPPER LEVEL ELY FLOW PREVENTING IT FROM DEVELOPING...AT LEAST THROUGH THE NEXT 48 HOURS. A TROPICAL WAVE ALONG 134W/135W FROM 5N TO 15N IS MOVING W ABOUT 10-15 KT. THE WAVE REMAINS RATHER WEAK WITH ONLY ISOLATED SHOWERS WITHIN 60 NM OF THE AXIS. ...ITCZ... ITCZ AXIS ALONG 7N79W 6N88W 10N103W 15N110W 12N120W 10N130W 10N140W. SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 120 NM S OF THE AXIS BETWEEN 82W-90W. SIMILAR CONVECTION EXISTS WITHIN 60 NM OF THE AXIS W OF 138W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 180 NM S OF THE AXIS BETWEEN 100W AND 103W...AND ALSO N OF THE AXIS BETWEEN 97W-101W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM S OF THE AXIS BETWEEN 125W-130W. ...DISCUSSION... W OF 130W... A MIDDLE/UPPER LEVEL TROUGH EXTENDS SW INTO THE AREA FROM 32N130W SW TO NEAR 21N140W...W OF THE AREA IT BECOMES A SHEAR AXIS. THE TROUGH IS MOVING E ABOUT 17 KT. MODERATE SUBSIDENCE AND ASSOCIATED DRY AIR IS OBSERVED WITHIN 300 NM SE OF THE TROUGH. UPPER LEVEL MOISTURE IS SEEN PUSHING SEWD INTO THE NORTHERN PORTION OF THE AREA BEHIND THE TROUGH. SLIGHT DIFFLUENCE TO THE SE OF THE TROUGH IS ENHANCING ITCZ CONVECTION SOME BETWEEN 127W-130W. THE TROUGH IS FORECAST TO LIFT NE AND DAMPEN OUT OVER THE NEXT 48 HOURS AS MID/UPPER LEVEL RIDGING BUILDS SW TO NEAR 130W AND N OF 20N. A NEARLY STATIONARY ELONGATED MID/UPPER LEVEL ANTICYCLONE IS LOCATED JUST W OF THE REGION NEAR 15N144W. STRONG EASTERLY UPPER LEVEL WINDS ARE NOTED FROM 3N-15N. AT THE SURFACE...A RIDGE EXTENDS SE FROM 31N137W TO 26N128W TO 22N120W. HIGH PRES COVERS THE AREA N OF 15N W OF 124W. BROKEN TO SCATTERED STRATOCUMULUS CLOUDS MOVING SW TO W WITH POSSIBLE ISOLATED SHOWERS ARE PRESENT NW OF A LINE FROM 21N120W TO 15N140W. E OF 130W... THE UPPER FLOW THROUGHOUT THIS AREA IS PRIMARILY BEING STEERED BY A LARGE UPPER LEVEL ANTICYCLONE CENTERED OVER THE GREAT PLAINS IN COMBINATION WITH A RATHER ELONGATED UPPER LEVEL CYCLONE OVER THE NW CARIBBEAN SEA S OF WESTERN CUBA. RIDGING FROM THE ANTICYCLONE EXTENDS SOUTHWARD TO NORTHERN MEXICO... WHILE THE UPPER FLOW TO THE W OF THE UPPER LEVEL CYCLONIC CIRCULATION EXTENDS W COVERING THE YUCATAN PENINSULA...GUATEMALA AND BELIZE AND HONDURAS. UPPER LEVEL DEBRIS MOISTURE FROM ITCZ CONVECTION IS BEING CHANNELED WESTWARD UNDER THE UPPER ELY FLOW TOWARDS AND OVER HERNAN. A MID/UPPER LEVEL RIDGE ALONG 88W S OF 11N IS MOVING W 10-15 KT. AT THE SURFACE A WEAK PRES PATTERN PREVAILS...WITH THE EXCEPTION OF THE GULF OF PAPAGAYO AND THE AREA FROM 10N TO 12N E OF 92W WHERE E WINDS OF 20 KT AND SEAS TO 8 FT WILL MOST LIKELY CONTINUE THROUGH AROUND THE NEXT 72 HOURS. ANOTHER TROPICAL WAVE E OF THE AREA OVER THE WESTERN CARIBBEAN SEA ALONG 79W WILL FURTHER ENHANCE THE LIFE SPAN OF THESE WINDS THROUGH THE NEXT 3 DAYS AS IT MOVES WESTWARD AT 15 KT ACROSS CENTRAL AMERICA AND INTO THE E PACIFIC WATERS. $$ AGUIRRE