000 AXPZ20 KNHC 072150 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC TUE OCT 07 2014 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2145 UTC. ...SPECIAL FEATURES... TROPICAL STORM SIMON DOWNGRADED TO A TROPICAL DEPRESSION CENTERED AT 27.9N 116.3W...OR ABOUT 75 MILES W OF PUNTA EUGENIA MEXICO AT 2100 UTC MOVING N-NE OR 030 DEG AT 06 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 MB. MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH GUSTS TO 40 KT. SIMON IS SPINNING DOWN WITHIN A BROAD AREA OF OVERCAST STRATOCUMULUS CLOUDS WITH SCATTERED MODERATE ISOLATED STRONG CONVECTION OBSERVED WELL NE OF THE CENTER OVER THE GULF OF CALIFORNIA TO THE N OF 29N WHERE RAINFALL ACCUMULATIONS OF 2 INCHES ARE STILL POSSIBLE. ASSOCIATED SWELLS WILL CONTINUE TO AFFECT PORTIONS OF THE NORTHERN BAJA CALIFORNIA PENINSULA AND SOUTHERN CALIFORNIA TONIGHT...AND THESE SWELLS MAY CAUSE LIFE-THREATENING SURF AND RIP CURRENTS. SIMON IS FORECAST TO WEAKEN TO A 30 KT REMNANT LOW PRESSURE CENTER LATER TONIGHT...AND FURTHER WEAKEN TO 20-25 KT ON WED. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS. ...TROPICAL LOWS AND WAVES... A TROPICAL WAVE IS ANALYZED N OF 07 ALONG 86.5W AND HAS BEEN PROGRESSING WESTWARD AT 10 KT OVER THE PAST 24 HOURS. ISOLATED MODERATE TO ISOLATED STRONG CONVECTION...WITH OCCASIONAL LIGHTNING...CONTINUES TO FLARE N OF THE ITCZ WITHIN ABOUT 150 NM OF THE WAVE AXIS. A 1010 MB LOW PRESSURE IS EMBEDDED IN THE MONSOON TROUGH AT 13N136W WITH SCATTERED MODERATE TO STRONG CONVECTION OBSERVED OVER AND WITHIN 180 NM TO THE N OF THE CENTER. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A 1009 MB LOW PRESSURE IS EMBEDDED IN THE MONSOON TROUGH OVER THE SW CARIBBEAN AT 11N82W. THE MONSOON TROUGH EXTENDS SW FROM THE LOW ACROSS COSTA RICA ALONG 10N TO THE PACIFIC COAST OF COSTA RICA AT 10N85W CONTINUING W THROUGH THE BASE OF A TROPICAL WAVE AT 08N96.5W TO 07N97W...THEN TURNS NW TO 10.5N111W...THEN W- SW TO 09N126W...THEN NW TO AN EMBEDDED 1010 MB LOW PRES AT 13N136W...WITH THE MONSOON TROUGH THEN CONTINUING SW TO BEYOND 12N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED ALONG THE EASTERN SEGMENT OF THE MONSOON TROUGH WITHIN 180 NM EITHER SIDE OF A LINE FROM 07N77W TO 09.5N91W TO 07N100W...THEN NARROWS AND CONTINUES TO THE S OF THE CENTRAL PORTION OF THE MONSOON TROUGH WITHIN 120 NM EITHER SIDE OF A LINE FROM 06N100W TO 09N1110W TO 08N125W TO 08N131W. ...DISCUSSION... AN UPPER LEVEL CYCLONE IS CENTERED NEAR 33N124W AND HAS AN UPPER TROUGH EXTENDING SW TO 21N133W WITH THE ASSOCIATED SOUTHWESTERLY UPPER FLOW SHEARING TROPICAL CYCLONE SIMON...AND ADVECTING THE DEBRIS MOISTURE FROM THE CYCLONE NE ACROSS THE SW CONUS. A UPPER ANTICYCLONE IS CENTERED AT 21N111W WITH AN UPPER RIDGE EXTENDING SW TO ANOTHER UPPER ANTICYCLONE AT 15N140W. UPPER DIFFLUENCE IS ENHANCING SCATTERED MODERATE CONVECTION WITHIN 120 NM OF A LOW LEVEL TROUGH EXTENDING FROM 10N119W TO 18N117W. THE TROUGH IS MOVING WESTWARD AND WILL MOVE UNDER THE UPPER RIDGE WITH LESS FAVORABLE CONDITIONS FOR CONVECTION ON WED. FURTHER W...UPPER DIFFLUENCE OVER THE E SEMICIRCLE OF THE ANTICYCLONE AT 15N140W IS SUPPORTING THE CONVECTION PREVIOUSLY DESCRIBED NEAR THE 1010 MB SURFACE LOW AT 13N136W. THIS FAVORABLE UPPER ENVIRONMENT MAY PERSIST FOR ANOTHER DAY OR SO. THE PREVIOUSLY MENTIONED LOW PRESSURE OVER THE SW CARIBBEAN IS EXPECTED TO MOVE ACROSS CENTRAL AMERICA ON WED EMERGING IN THE EPAC NEAR 11N87W ON WED NIGHT. THE LOW WILL THEN MOVE NW TO NEAR 11N88W ON THU...NEAR 11N90W ON FRI...NEAR 11N91W ON SAT AND NEAR 13N92W ON SUN. CONDITIONS WILL BECOME MORE FAVORABLE FOR STRENGTHENING LATE IN THE PERIOD. GULF OF TEHUANTEPEC...THE NORTHERLY NOCTURNAL DRAINAGE FLOW ACROSS THE GULF OF TEHUANTEPEC IS EXPECTED TO INCREASE TO 20-25 KT LATE WED NIGHT THROUGH LATE MORNING ON THU WITH SEAS BUILDING TO 8 FT. THE NORTHERLY DRAINAGE FLOW IS LIKELY TO INCREASE OVER THE UPCOMING WEEKEND IF THE LOW PRESSURE ALREADY DISCUSSED TO THE SE OF TEHUANTEPEC STRENGTHENS. $$ NELSON