000 AXPZ20 KNHC 082204 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC FRI AUG 08 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... HURRICANE HERNAN WAS CENTERED NEAR 14.8N 120.9W OR ABOUT 910 NM ...1465 KM SOUTHWEST OF THE SOUTHERN TIP OF BAJA CALIFORNIA AT 08/1500 UTC MOVING W AT 10 KT. MAXIMUM SUSTAINED WIND SPEED HAS INCREASED TO 75 KT WITH GUSTS TO 90 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 980 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 BOTH INFRA-RED AND VISIBLE SATELLITE IMAGERY. THIS IS APPARENT BY ITS MUCH BETTER DEFINED EYE FEATURE CURRENTLY BEING DISPLAYED ON THE IMAGERY. VERY DEEP BURSTS OF COLD TOP CONVECTION IS OVER AND WITHIN ALL QUADRANTS OF THE EYE. THIS CONVECTION CONSISTS OF NUMEROUS STRONG WITHIN 60 NM NE AND SE OF THE EYE. SCATTERED STRONG CONVECTION IS ELSEWHERE WITHIN 150 NM IN THE SE QUADRANT...90 NM E QUADRANT AND WITHIN 60 NM IN THE NE QUADRANT. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 175 NM SW THROUGH W OF THE EYE. AN OUTER RAINBAND CONSISTING OF SCATTERED MODERATE CONVECTION IS WITHIN 30 NM EITHER SIDE OF A LINE FROM 11N126W TO 11N124W TO 11N122W. HERNAN IS FORECAST TO REMAIN A HURRICANE THROUGH THE NEXT 72 HOURS HOURS BEFORE ENCOUNTERING COOLER SEA SURFACE TEMPERATURES CAUSING IT TO UNDERGO WEAKENING. LOW PRES NEAR 9N90W 1008 MB IS MOVING W 13 KT. BOTH CLOUDINESS AND CONVECTION CONSISTING OF THE SCATTERED MODERATE TO STRONG TYPE ARE BETWEEN 150-300 NM SW OF THE LOW. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120 NM OF THE LOW IN THE N SEMICIRCLE. VISIBLE IMAGERY FROM DURING THE DAY SHOWS EVIDENCE OF CYCLONIC TURNING IN THE LOW CLOUD FIELD FROM 6N-13N BETWEEN 86W-92W. NWP MODELS SUGGEST THAT THIS SYSTEM IS LIKELY TO ORGANIZE FURTHER OVER THE NEXT 48 HOURS AS IT MOVES IN A GENERAL WNW TRACK. ...TROPICAL WAVES... THE SOUTHERN PORTION OF A TROPICAL WAVE HAS MOVED INTO THE FAR EASTERN PORTION OF THE AREA N OF 6N ALONG 83W...MOVING W 10-15 KT. SCATTERED STRONG CONVECTION IS WITHIN 60 NM W OF THE WAVE FROM 7N-8N. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 240 NM E OF THE WAVE FROM 4N-8N. A TROPICAL WAVE IS ALONG 107W/108W FROM 5N TO 15N MOVING W ABOUT 13 KT. AN ASSOCIATED 1008 MB LOW IS LOCATED ON THE WAVE NEAR 11N. SCATTERED MODERATE ISOLATED/STRONG CONVECTION IS WITHIN 60 NM EITHER SIDE OF THE WAVE...AND ALSO E OF THE WAVE FROM 10N-13N. LITTLE CHANGE IN BOTH STRUCTURE AND ORGANIZATION OF CONVECTION HAS BEEN OBSERVED WITH THE WAVE DURING THE DAY AS IT REMAINS UNDER MODERATE ELY SHEAR...HOWEVER SOME SLOW DEVELOPMENT IS STILL POSSIBLE WITH THIS WAVE AS IT MOVES INTO A MORE FAVORABLE UPPER LEVEL ENVIRONMENT DURING THE NEXT 48 HOURS. A TROPICAL WAVE ALONG 139W FROM 6N TO 15N IS MOVING W ABOUT 10-15 KT. A 1010 MB LOW IS IDENTIFIED ON THE WAVE NEAR 10N. THIS SYSTEM IS ENHANCING SCATTERED STRONG ITCZ CONVECTION WITHIN 120 NM TO ITS E...AND HAS THE POTENTIAL TO BECOME A POSSIBLE TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES W OF THE AREA. ...ITCZ... ITCZ AXIS ALONG 9N85W 8N95W 11N107W WHERE IT TEMPORARILY ENDS. IT THEN BEGINS AGAIN AT 12N121W...AND EXTENDS TO 11N125W 12N134W 10N140W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 60 NM EITHER SIDE OF THE AXIS BETWEEN 130W-134W. ...DISCUSSION... W OF 130W... A MIDDLE/UPPER LEVEL TROUGH EXTENDS SW INTO THE AREA FROM 32N130W SW TO A SOMEWHAT ELONGATED BUT SMALL MID/UPPER LEVEL CYCLONIC CIRCULATION DROPPING S 15 KT JUST W OF THE AREA NEAR 23N141W. W OF THE AREA...THE TROUGH BECOMES A SHEAR AXIS TO JUST SE OF THE HAWAIIAN ISLANDS. THE TROUGH IS MOVING SE ABOUT 15 KT. ITS SURFACE REFLECTION IS ANALYZED AS A COLD FRONT ENTERING THE FAR NW PORTION OF THE AREA FROM 32N133W TO 32N141W...WHERE IT BECOMES A STATIONARY FRONT NORTHWESTWARD FROM THERE. THE FRONT IS MOVING SSE 15-20 KT...AND IS FORECAST TO RAPIDLY WEAKEN AS IT MOVES TO JUST NE OF THE AREA IN ABOUT 18-24 HOURS. A BROKEN TO SCATTERED LAYER OF COLD AIR STRATOCUMULUS CLOUDS WITH POSSIBLE ISOLATED SHOWERS IS SURGING S BEHIND THE COLD FRONT. MODERATE SUBSIDENCE AND ASSOCIATED DRY AIR IS OBSERVED TO THE SE AND S OF THE MID/UPPER TROUGH TO NEAR 16N WHERE ITCZ MOISTURE IS EVIDENT. UPPER LEVEL MOISTURE IS SEEN PUSHING SEWD INTO THE NORTHERN PORTION OF THE AREA BEHIND THE TROUGH N OF 20N. SLIGHT DIFFLUENCE TO THE SE OF THE TROUGH IS ENHANCING ITCZ CONVECTION NEAR 130W. THE TROUGH IS FORECAST TO LIFT NE AND DAMPEN OUT OVER THE NEXT 48 HOURS AS MID/UPPER LEVEL RIDGING BUILDS SOUTHWEST- WARD FROM THE SW UNITED STATES TO N OF 20N. A NEARLY STATIONARY ELONGATED MID/UPPER LEVEL ANTICYCLONE IS LOCATED W OF THE REGION ALONG 155W N OF 22N. VERY PRONOUNCED MID/UPPER LEVEL RIDGING EXTENDS ALONG 15N...AND IS WHAT IS CURRENTLY STEERING HERNAN IN WESTWARD TRACK. MODERATE TO STRONG UPPER LEVEL E TO SE WINDS NOTED ON SATELLITE-DERIVED WIND DATA S OF 15N. AT THE SURFACE... A RIDGE IS BRIDGING SOUTHEASTWARD ACROSS THE ABOVE MENTIONED FRONT THROUGH 28N134W TO 27N130W AND CONTINUES TO E OF 130W. HIGH PRES COVERS THE AREA N OF 21N W OF 124W. BROKEN TO SCATTERED STRATOCUMULUS CLOUDS MOVING SW TO W WITH POSSIBLE ISOLATED SHOWERS ARE PRESENT NW OF A LINE FROM 20N130W TO 16N140W...EXCEPT FOR THE AREA S OF THE FRONT TO 27N WHERE SKIES ARE RELATIVELY CLOUD FREE. 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 MID/UPPER LEVEL CYCLONE OVER NW CUBA. A TROUGH EXTENDS FROM THE CYCLONE SW TO THE GULF OF HONDURAS...AND SW TO A MID UPPER LEVEL CYCLONIC CIRCULATION MOVING W 18 KT ALONG THE ITCZ NEAR 9N93W. RIDGING FROM THE ANTICYCLONE EXTENDS SW TO NW MEXICO...WHILE THE UPPER FLOW TO THE W OF THE UPPER CYCLONE AND TROUGH EXTENDS W COVERING THE YUCATAN PENINSULA...GUATEMALA AND BELIZE. UPPER LEVEL DEBRIS MOISTURE FROM ITCZ CONVECTION CONTINUES TO BE ADVECTED WESTWARD UNDER THIS UPPER LEVEL FLOW ENVIRONMENT TO BEYOND HERNAN. A MID/UPPER LEVEL RIDGE FROM THE GULF OF TEHUANTEPEC TO 10N92W O 6N91W IS MOVING W 13 KT. AT THE SURFACE...THE EASTERN PORTION OF THE SURFACE RIDGE MENTIONED ABOVE UNDER W OF 130W PROTRUDES ESE TO NEAR 28N120W. A WEAK PRES PATTERN PREVAILS...WITH THE EXCEPTION OF THE GULF OF PAPAGAYO AND THE AREA FROM 10N TO 13N E OF 90W WHERE E WINDS OF 20 KT AND SEAS TO 8 FT ARE NOTED. AS THE 1008 MB LOW NEAR 9N90W AND TROPICAL WAVES OF THE DISCUSSION AREA PROPAGATE WESTWARD ACROSS CENTRAL AMERICA...AND INTO THE FAR EASTERN WATERS OF THE THE AREA AS DEPICTED BY GLOBAL MODEL GUIDANCE. $$ AGUIRRE