000 AXPZ20 KNHC 070314 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC TUE JUL 07 2009 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0300 UTC. ...SPECIAL FEATURE... TROPICAL STORM BLANCA WAS CENTERED NEAR 18.2N 113.8W AT 07/0300 UTC OR 410 MILES SW OF THE SOUTHERN TIP OF BAJA CALIFORNIA MOVING WNW OR 295 DEG AT 9 KT. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 50 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 998 MB. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP3/WTPZ33 KNHC FOR MORE DETAILS. BLANCA IS EXHIBITING A PRETTY WELL DEFINED SYMMETRICAL STRUCTURE IN ITS CLOUD PATTERN. BANDING FEATURES CONTINUE TO BE APPARENT ON LAST VISIBLE IMAGERY...ALTHOUGH SOME OF ITS EARLIER OBSERVED COLD TOP CONVECTION HAS WEAKENED NEAR THE CENTER. THE BANDING FEATURES ARE COMPRISED OF SCATTERED STRONG CONVECTION WITHIN 45 NM EITHER SIDE OF A LINE FROM 15N112W TO 18N111W...THEN BECOMES SCATTERED MODERATE/ISOLATED STRONG CONVECTION NW TO 18N112W TO 19N113.5W TO 18N114W. AN INNER BAND IS MADE UP OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION WITHIN 30 NM EITHER SIDE OF LINE FROM 17N116W TO 16N114W TO 17N113W. BLANCA IS CURRENTLY MOVING OVER 27-28C SEA SURFACE TEMPERATURE IN A LOW SHEAR ENVIRONMENT. HOWEVER...THE CYCLONE IS STILL FORECAST TO MOVE OVER SUB-26C WATERS WITHIN 24 HOURS. AS A RESULT...THE FORECAST CALLS FOR ONLY SLIGHT INTENSIFICATION THROUGH TUE EVENING...FOLLOWED WEAKENING THEREAFTER THROUGH THE REST OF THE WEEK. ...TROPICAL WAVES... TROPICAL WAVE OVER THE FAR E PORTION OF THE DISCUSSION AREA IS ALONG 91W N OF 2N TO SW GUATEMALA MOVING W ABOUT 13 KT. ONLY ISOLATED WEAKENING CONVECTION REMAINS WITHIN 120 NM E OF THE AXIS FROM 6N-7N. SIMILAR CONVECTION IS ALONG THE ITCZ BETWEEN 89W-91W. TROPICAL WAVE IS ALONG 107W FROM 2N-14N MOVING W AT 15 KT. ISOLATED WEAK CONVECTION IS WITHIN 180 NM E OF THE WAVE AXIS FROM 4N-9N. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 8N78W 10N91W 8N100W 9N110W 9N130W 10N140W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120 NM N OF THE AXIS BETWEEN 87W-96W...AND ALSO FROM 6N-12N BETWEEN 96W-102W. ...DISCUSSION... A WELL PRONOUNCED ELONGATED E TO S MID/UPPER LEVEL ANTICYCLONE IS CENTERED OVER NE MEXICO WITH A RIDGE EXTENDING W TO 28N118W ...AND THEN SW TO 25N136W. A LONGWAVE TROUGH IS EVIDENT WELL W OF THE REGION. SW UPPER LEVEL FLOW BETWEEN THE TROUGH AND THE RIDGE CONTINUES TO ADVECT DEEP TROPICAL UPPER LEVEL MOSITURE NEWD FROM THE CENTRAL PACIFIC TO JUST NW OF THE FAR NW CORNER OF THE AREA. OTHERWISE...SATELLITE WATER VAPOR IMAGERY SHOWS THAT THE VAST MAJORITY OF THE DISCUSSION AREA W OF A LINE FROM CENTRAL BAJA CALIFORNIA TO 20N121W TO 10N132W IS UNDER MODERATE SUBSIDENCE MAINTAINING STABLE ENVIRONMENTAL CONDITIONS AS INDICATED BY THE PRESENCE OF PATCHES OF SCATTERED TO BROKEN STRATOCUMULUS CLOUDS MOVING SW AROUND THE ERN PERIPHERY OF SURFACE HIGH PRES PRESENT N OF 19N W OF 119W WITH THE PARENT HIGH CENTER LOCATED N OF THE AREA. THE HIGH PRES FEATURE WILL BE WHAT DRIVES TROPICAL STORM BLANCA ON A MOSTLY WNW TRACK DURING THE NEXT 24 HOURS. ANOTHER UPPER-LEVEL HIGH ANCHORED OVER THE SW CARIBBEAN DOMINATES CENTRAL AMERICA AND THE FAR E PORTION OF THE DISCUSSION AREA...AND IS HELPING TO INDUCE SOME CONVECTION ALONG THE ITCZ AXIS AND NEAR THE ABOVE MENTIONED TROPICAL WAVES. OTHERWISE MODERATE TO STRONG SUBSIDENCE WITH DRY STABLE AIR AT THE MID AND UPPER LEVELS OF THE ATMOSPHERE COVERS MOST OF THE AREA N OF 15N W OF 120W. OVER THE REMAINDER OF THE AREA ABUNDANT UPPER LEVEL MOISTURE IS OBSERVED ON SATELLITE IMAGERY...PRIMARILY ATTRIBUTED TO UPPER LEVEL ELY ADVECTING UPPER LEVEL MOSITURE ORIGINATING FROM CONVECTION ASSOCIATED WITH BLANCA WESTWARD. THE MOISTURE IS ALSO BEING ENHANCED BY DEBRIS CLOUDINESS FROM ITCZ CONVECTION E OF 110W. THE COMBINATION OF HIGH PRES AS STATED ABOVE AND A SURFACE TROUGH OVER THE FAR WRN PORTION OF THE AREA EXTENDING FROM 7N140W TO 13N138W IS RESULTING IN AN AREA OF NE-E TRADES OF 20 KT TO BE CONFINED FROM 13N-21N W OF 130W. THESE TRADES ARE FORECAST TO GRADUALLY DIMINISH IN AREAL COVERAGE DURING THE NEXT 48 HRS WITH THE TROUGH HAVING EXITED THE AREA. ONGOING SRN HEMISPHERIC FRONTAL SYSTEMS CONTINUE TO SEND LONG-PERIOD SWLY SWELLS NWD WITH PERIODS OF 14-15 SECONDS BUILDING THE SEAS INTO THE 8-10 FT RANGE ELSEWHERE E OF THE LINE FROM 21N118W TO 11N118W TO THE EQUATOR AT 122W. THESE CONDITIONS ARE FORECAST TO SLOWLY DIMINISH THROUGH THE NEXT 48 HOURS. $$ AGUIRRE