000 AXPZ20 KNHC 081532 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC WED JUL 08 2009 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 1500 UTC. ...SPECIAL FEATURE... BLANCA WAS DOWNGRADED TO A TROPICAL DEPRESSION AT 0900 UTC AND IS EXPECTED TO BECOME A REMNANT LOW LATER TODAY. AT 1500 UTC... IT IS CENTERED NEAR 20.8N 120.1W OR ABOUT 580 NM...1080 KM... WEST OF THE SOUTHERN TIP OF BAJA CALIFORNIA MOVING WNW OR 290 DEG AT 9 KT...AND THIS MOTION IS EXPECTED TO CONTINUE UNTIL DISSIPATION ON FRI. MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH GUSTS TO 40 KT. MINIMUM PRESSURE IS 1005 MB. SEE LATEST NHC FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP3/WTPZ33 KNHC FOR MORE DETAILS. CONVECTION NEAR BLANCA HAS RAPIDLY DECREASED AND IS NOW A TIGHT SWIRL OF LOW CLOUDS MOVING OVER 22-23C SEA SURFACE TEMPERATURES. ...TROPICAL WAVES... TROPICAL WAVE N OF 6N TO THE COAST OF EL SALVADOR ALONG 89W MOVING W 10-15 KT. A CLUSTER OF MODERATE TO ISOLATED STRONG CONVECTION IS BEHIND THE WAVE AXIS WITHIN 50 NM OF 10.5N88W. SIMILAR CONVECTION IS OBSERVED AHEAD OF THIS FEATURE CURRENTLY AFFECTING THE GULF OF TEHUANTEPEC. IN ADDITION...THE WAVE IS GENERATING A LARGE AREA OF SHOWERS AND TSTMS OVER THE NW CARIBBEAN. TROPICAL WAVE FROM 3N-14N ALONG 106W MOVING W 10-15 KT. SCATTERED TO ISOLATED STRONG CONVECTION IS NOTED WHERE THE WAVE MEETS THE ITCZ AXIS. TOPICAL WAVE FROM 4N-13N ALONG 118W/119W. SCATTERED TO ISOLATED STRONG CONVECTION IS WITHIN 200 NM E OF AXIS MAINLY ALONG THE ITCZ. ...ITCZ... THE ITCZ AXIS IS ALONG 08N78W TO 10N100W TO 08N113W TO 09N130W TO 10N140W. SCATTERED TO NUMEROUS MODERATE TO ISOLATED STRONG CONVECTION IS NOTED WITHIN 170 NM S OF AXIS E OF 80W. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION CAN BE FOUND FROM 06N TO 11N BETWEEN 103W AND 110W...AND BETWEEN 115W AND 119W. ...DISCUSSION... AN UPPER-LEVEL ANTICYCLONIC CIRCULATION REMAINS CENTERED OVER NW MEXICO NEAR 30N110W WITH A RIDGE EXTENDING OVER THE NE PORTION OF THE FORECAST AREA MAINLY N OF 20N E OF 122W. BLANCA IS ON THE SOUTH SIDE OF THIS RIDGE...WITH WATER VAPOR IMAGERY SHOWING A MID/UPPER-LEVEL LOW NEAR 19N131W. ANOTHER UPPER-LEVEL ANTICYCLONIC CIRCULATION IS NOTED OVER SE MEXICO AND NORTHERN CENTRAL AMERICA SUPPORTING CONVECTION OVER THE GULF OF TEHUANTEPEC...NEAR THE TROPICAL WAVE WITH AXIS ALONG 89W...AND ALONG THE ITCZ. ACCORDING TO THE COMPUTER MODELS...THE UPPER RIDGE AXIS TO THE N OF BLANCA IS EXPECTED TO SHIFT NEWD AS A TROUGH MOVES INTO NW WATERS LATE TODAY. AT THE SURFACE...THE RIDGE OVER NW WATERS WILL WEAKEN IN RESPONSE TO THE INCREASED TROUGHING ALOFT. AS A RESULT...THE TRADE WINDS WILL DIMINISH BELOW 20 KT AS THE PRES GRADIENT...ASSOCIATED WITH THIS SURFACE RIDGE...RELAXES. BASED ON THE SSMI AND AN EARLIER QSCAT PASS WILL KEEP THE TRADE WINDS TO 20 KT DURING THE NEXT 24 HOURS. ALTHOUGH THE REMNANTS OF BLANCA SHOULD CONTINUE TO WEAKEN UNTIL THEY DISSIPATE IN ABOUT 48-72 HR...AN AREA OF NE WINDS UP TO 20 KT WILL PERSIST TO THE NW QUADRANT DUE TO THE PRES GRADIENT BETWEEN THE ABOVE MENTIONED SURFACE RIDGE AND WHAT IS LEFT OF BLANCA. LARGE SWELLS FROM THE SOUTHERN HEMISPHERE CONTINUE TO CROSS THE EQUATOR OVER THE S PORTION OF THE DISCUSSION AREA. THESE CONDITIONS ARE EXPECTED TO GRADUALLY SUBSIDE DURING THE NEXT COUPLE OF DAYS. $$ GR