000 AXPZ20 KNHC 240904 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC THU SEP 24 2009 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0715 UTC. ...SPECIAL FEATURE... TROPICAL STORM NORA IS CENTERED NEAR 17.2N 119.2W AT 24/0900 UTC MOVING WNW OR 300 DEG AT 4 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000 MB. MAXIMUM SUSTAINED WIND SPEED HAS DECREASED TO 45 KT WITH GUSTS TO 55 KT. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP2/WTPZ22 KNHC FOR MORE DETAILS. NUMEROUS MODERATE TO STRONG CONVECTION CAN BE FOUND WITHIN 45 NM NW QUADRANT AND SCATTERED MODERATE CONVECTION LIES WITHIN 120 NM E SEMICIRCLE. CIRRUS OUTFLOW FROM NORA IS MOVING INTO THE SOUTHERN EDGE OF A 50 KT WESTERLY JET AND BEING TRANSPORTED NE TOWARD THE SOUTHERN BAJA PENINSULA. NORA IS FORECAST TO MAINTAIN ITS INITIAL INTENSITY THROUGH THE DAY TODAY BEFORE SLOWLY DIMINISHING TO A TROPICAL DEPRESSION EARLY SAT MORNING AS IT MOVES W TOWARD THE UPPER JET AND AN INCREASINGLY STABLE ENVIRONMENT. ...THE ITCZ... THE INTERTROPICAL CONVERGENCE ZONE IS ALONG 08N78W TO 10N105W TO 15N115W TO 11N126W TO 09N140W. ISOLATED MODERATE TO STRONG CONVECTION CAN BE FOUND WITHIN 210 NM N OF THE ITCZ AXIS BETWEEN 125W TO 134W. SCATTERED MODERATE CONVECTION LIES WITHIN 180 NM S OF THE ITCZ AXIS BETWEEN 87W AND 96W AND WITHIN 150 NM S OF THE ITCZ AXIS BETWEEN 113W AND 115W. ...DISCUSSION... W OF 120W... A 1007 MB LOW PRES SYSTEM EMBEDDED IN THE ITCZ NEAR 10N135W MOVING W AT 7 KT HAS SPAWNED NUMEROUS MODERATE TO STRONG CONVECTION WITHIN 45 NM NW QUADRANT AND SCATTERED MODERATE WITHIN 120 NM E SEMICIRCLE. MUCH OF THE 0334 UTC QUIKSCAT PASS HAD RAIN FLAGGED RETRIEVALS UNDER THE STRONG CONVECTION...BUT THERE WERE ENOUGH RELIABLE RETRIEVALS IN THE SOUTHERN SEMICIRCLE OF THE LOW TO BELIEVE THE SOUTHERLY INFLOW INTO THE SYSTEM IS IN THE 20 TO 30 KT RANGE. TO THE NORTH OF THE LOW...THE SAME QUIKSCAT PASS SHOWED A BROAD AREA OF 20 TO 25 KT WINDS IN THE NE QUADRANT BETWEEN THE LOW AND THE HIGH PRES RIDGE STRETCHED FROM THE 1023 MB LOW PRES NEAR 32N136W AND 20N125W. AN ENVISAT PASS FROM WED AFTERNOON SHOWS SEAS WERE AT 8 FT IN THIS AREA NE OF THE LOW AND SEAS IN THE SE QUADRANT WERE HIGHER...IN THE 9-10 FT RANGE...AS EXPECTED BASED ON THE WINDS. THERE IS GOOD AGREEMENT IN THE FORECAST GUIDANCE TO SLOWLY CARRY THIS SYSTEM NW OVER THE NEXT 48 HOURS WITH LITTLE FURTHER INTENSIFICATION. OVER NORTH WATERS...SHORTWAVE ENERGY ALOFT LEFT BEHIND BY BOTH THE POSITIVELY TILTED UPPER TROUGH OVER THE CENTRAL U.S. AND NW MEXICO AND THE WEAKENING DEEP-LAYER TROUGH ALONG 133W N OF 32N WILL JOIN TOGETHER TO FORM AND UPPER LOW OVER N WATERS OVER THE NEXT TWO DAYS. THIS WILL PREVENT THE SURFACE RIDGE OVER N WATERS FROM INTENSIFYING APPRECIABLY. IT WILL ALSO DISRUPT THE STRONG SUBSIDENCE N OF 24N E OF 135W WILL BREAK UP SOME OF THE DENSE STRATOCUMULUS FOUND THERE CURRENTLY. THE SURFACE RIDGE AXIS DESCRIBED ABOVE WILL SHIFT EASTWARD OVER THE NEXT TWO DAYS AND EASTERLY WINDS INDUCED BY THE MERIDIONAL PRES GRADIENT WILL INCREASE TO 20 KT OVER NW WATERS BY FRI MORNING. THIS AREA ALSO WILL SEE THE ARRIVAL OF 15-16 SECOND PERIOD NW SWELL LATE FRI. E OF 120W... THE WEAKENING COLD FRONT ASSOCIATED WITH THE AFOREMENTIONED POSITIVELY TILTED TROUGH ALOFT OVER THE CENTRAL U.S. AND NW MEXICO HAS BROUGHT 20 KT WINDS TO THE GULF OF CALIFORNIA N OF 27N AS SEEN IN THE 0148 QUIKSCAT PASS. THESE WINDS WILL DIMINISH BELOW 20 KT LATER TODAY. THIS FRONT HAS ALSO BROUGHT NORTHERLY FLOW IN THE 20-25 KT RANGE INTO THE GULF OF TEHUANTEPEC ACCORDING TO THE 0012 UTC QUIKSCAT PASS. WINDS HERE ARE EXPECTED TO DIMINISH BELOW 20 KT FRI NIGHT AS THE HIGH PRES BEHIND THE COLD FRONT ERODES...WEAKENING THE PRES GRADIENT. THE 50 KT WESTERLY UPPER JET FROM 22N130W TO 27N110W WILL MOVE LITTLE AND CONTINUE TO INHIBIT CONVECTION IN NW MEXICO THE NEXT FEW DAYS. SCATTERED MODERATE TO STRONG CONVECTION CURRENTLY LIES E OF 107W TO MEXICAN COAST FROM 19N TO 21N IN THE DIFFLUENT AREA ALONG THE UPPER RIDGE AXIS EXTENDING FROM AN ANTICYCLONE OVER THE GULF OF MEXICO NEAR 26N92W SOUTHWESTWARD TO 17N113W. ELSEWHERE...BROADLY DIFFLUENT FLOW BETWEEN THIS RIDGE AXIS AND A WEAK UPPER LOW CENTERED NEAR THE GALAPAGOS ISLANDS IS SUPPORTING THUNDERSTORMS NEAR THE ITCZ WITH SCATTERED MODERATE CONVECTION FOUND WITHIN 180 NM S OF THE ITCZ AXIS BETWEEN 87W AND 96W AS WELL AS WITHIN 150 NM OF THE COAST FROM SOUTHERN GUATEMALA TO THE BORDER OF NICARAGUA AND COSTA RICA FROM 11N TO 14N. $$ SCHAUER CLARK