000 AXPZ20 KNHC 240332 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC THU SEP 24 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 0315 UTC. ...SPECIAL FEATURE... TROPICAL STORM NORA IS CENTERED NEAR 17.0N 119.1W AT 24/0300 UTC MOVING WNW OR 295 DEG AT 6 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 997 MB. MAXIMUM SUSTAINED WIND SPEED HAS INCREASED TO 50 KT WITH GUSTS TO 60 KT. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP2/WTPZ22 KNHC FOR MORE DETAILS. DURING THE AFTERNOON AND EARLY EVENING HOURS NORA HAD REVEALED AN INTENSIFICATION TREND AS BOTH BANDING FEATURES AND CONVECTION HAD BECOME SIGNIFICANTLY WELL DEPICTED WITH EVEN A SMALL CENTRAL DENSE OVERCAST (CDO). HOWEVER...DURING THE LAST FEW SATELLITE IMAGES BANDING FEATURE NOTED EARLIER HAVE WEAKENED AS CONVECTION HAS WARMED. ONLY SCATTERED STRONG CONVECTION REMAINS WITHIN 45 NM OF THE CENTER IN THE NW QUADRANT. SCATTERED MODERATE/ISOLATED STRONG IS WITHIN 60 NM IN THE SE QUADRANT...WHILE SCATTERED MODERATE CONVECTION IS ELSEWHERE WITHIN 90 NM N SEMICIRCLE OF THE CENTER. THE CYCLONE WILL ONLY SLIGHTLY INTENSIFY THROUGH THE NEXT 24 HOURS BEFORE SHEAR INCREASES FROM THE SOUTHWEST OR WEST DUE TO A LARGE EASTERN PACIFIC TROUGH...AND NORA REACHES COOLER SEA SURFACE TEMPERATURES. THE OFFICIAL INTENSITY FORECAST THEN WEAKENS NORA TO A DEPRESSION JUST AFTER 48 HOURS. ...THE ITCZ... THE INTERTROPICAL CONVERGENCE ZONE IS ALONG 09N79W TO 10N90W TO 10N100W TO 14N115W TO 10N130W TO 9N140W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120 NM S OF THE AXIS BETWEEN 133W-138W AND WITHIN 60 NM OF THE AXIS BETWEEN 129W-133W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM S OF AXIS BETWEEN 100W-104W AND BETWEEN 106W-112W. ...DISCUSSION... AT THE SURFACE...A 1021 MB HIGH LOCATED NEAR 33N130W EXTENDS A RIDGE SE ACROSS THE FAR NE PORTION TO NEAR 26N117W. A SURFACE TROUGH...REMNANTS OF FORMER TROPICAL STORM MARTY...IS ALONG 137W FROM 21N TO 27N MOVING W 10 KT. STABLE ENVIRONMENTAL CONDITIONS AROUND THE TROUGH ARE PREVENTING ANY CONVECTION FROM DEVELOPING ALONG OR NEAR IT. HIGH PRES COVERS THE AREA NW AND N OF TROPICAL STORM NORA. ONLY SCATTERED TO BROKEN STRATOCUMULUS CLOUDS WITH POSSIBLE ISOLATED SHOWERS ARE SEEN WITHIN 60 NM NW OF THE TROUGH. EARLIER NE TO E WINDS OF 15-20 KT NOTED ON EITHER SIDE OF THE TROUGH ARE DIMINISHING AS THE TROUGH MOVES FURTHER W AWAY FROM THE HIGH CENTER OF 1021 MB. ALOFT...AN ELONGATED MID/UPPER LEVEL TROUGH EXTENDS SW INTO THE AREA AT 32N110W..AND CONTINUES TO 28N116W. A SMALL MID/UPPER LEVEL LOW MOVING NE ABOUT 15 KT IS NEAR 29N131W. A TROUGH EXTENDS FROM THE LOW SE TO NEAR 19N126W. BROAD MID/UPPER LEVEL RIDGING COVERS THE AREA SW AND W OF THIS LOW WITH A MEAN CENTER NEAR 13N132W. A RATHER PERSISTENT JET STREAM BRANCH ENTERS THE AREA THROUGH 23N140W...AND EXTENDS TO 23N137W TO 24N119W AND NE TO ACROSS CENTRAL BAJA CALIFORNIA AND TO THE E AND SE OF THE MID/UPPER LEVEL TROUGH. MAXIMUM WIND SPEEDS WITH THE JET ARE 50-60 KT. THIS JET IS TRANSPORTING UPPER LEVEL MOISTURE IN THE FORM OF SCATTERED TO BROKEN HIGH CLOUDS ENE TOWARDS SOUTHERN BAJA CALIFORNIA AND NW MEXICO. MODERATE TO STRONG SUBSIDENCE IS MAINTAINING STABLE CONDITIONS N OF THE JET STREAM ...AND E OF 138W. A LAYER OF BROKEN TO OVERCAST STRATOCUMULUS CLOUDS IS NOTED WITHIN THIS AREA. THE FIRST COLD FRONT OF THIS FALL SEASON IS MOVING SLOWLY SE ACROSS THE WESTERN GULF OF MEXICO. HIGH PRES BEHIND IT IS CREATING A GRADIENT THAT SUPPORTS 20 KT NLY WINDS OVER THE NORTHERN PORTION OF THE GULF OF CALIFORNIA. THIS WILL BE A SHORT-LIVED EVENT AND WINDS ARE EXPECTED TO DIMINISH TO BELOW 20 KT IN ABOUT 24 TO 30 HOURS. THE SAME FRONTAL SYSTEM IS EXPECTED TO BRING 20 TO 25 KT NORTHERLY FLOW THROUGH THE BAY OF CAMPECHE INTO THE GULF OF TEHUANTEPEC OVERNIGHT TONIGHT AND CONTINUE THROUGH THE FORECAST PERIOD. A COLD FRONT JUST NW OF THE REGION ASSOCIATED WITH LARGE DEEP LAYER TROUGH N OF THE REGION IS BECOMING STATIONARY AS CLEARLY OBSERVED IN SATELLITE IMAGERY. THIS FRONT IS FORECAST TO BECOME DIFFUSE THROUGH FRI AS NW TO SE RIDGING TAKES PRECEDENCE OVER THE AREA. A BROAD AREA OF SCATTERED SHOWERS AND TSTMS HAS BECOME EVIDENT JUST N OF THE ITCZ BETWEEN 130W-136W WITH A WEAK LOW NEAR 10N134W MOVING W ABOUT 7 KT. THIS AREA IS UNDER THE AREA OF BROAD MID/UPPER LEVEL RIDGING MENTIONED ABOVE...AND THE POTENTIAL FOR SOME SLOW DEVELOPMENT IS POSSIBLE OVER THE NEXT COUPLE OF DAYS AS GLOBAL MODELS SUGGEST. A WELL PRONOUNCED MID/UPPER ANTICYCLONE CENTERED OVER INLAND MEXICO NEAR 22N109W EXTENDS A RIDGE SW TO JUST EAST OF TROPICAL STORM NORA. THE UPPER PATTERN WITH THE RIDGE IS DIFFLUENT ALONG AND S OF THE RIDGE AXIS...AND CONTINUES TO SUPPORT SCATTERED MODERATE CONVECTION ALONG AND WITHIN 45 NM OF THE PACIFIC COAST OF MEXICO BETWEEN 104W AND 106W. SLY UPPER LEVEL WINDS ON THE WESTERN PERIPHERY OF THE RIDGE HAVE BECOME LIGHTER OVER THE PAST 24 HOURS ALLOWING FOR EXCELLENT OUTFLOW OF CONVECTION ASSOCIATED WITH TROPICAL STORM NORA. MID/UPPER RIDGING EXTENDS NW TO SE OVER AND ALONG CENTRAL AMERICA SUPPLYING UPPER LEVEL VENTILATION OF EARLIER DAYTIME SCATTERED MODERATE/ISOLATED CONVECTION NOTED OVER PARTS OF CENTRAL AMERICA. NE UPPER LEVEL WINDS TO THE S OF THE RIDGE ARE STEERING ANY CONVECTION THAT FORMS OVER LAND IN A GENERAL SOUTHWARD DIRECTION INCLUDING CONVECTION ALONG AND NEAR THE ITCZ. A SUBSIDENCE ZONE...ABOUT 175 NM WIDE...IS NOTED S OF MEXICO AND CENTRAL AMERICA BETWEEN 88W AND 95W. $$ AGUIRRE