000 AXPZ20 KNHC 110256 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC SUN SEP 11 2011 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0200 UTC. ...SPECIAL FEATURE... A SURFACE LOW PRESSURE EMBEDDED IN THE MONSOON TROUGH NEAR 15.5N117.5W IS ESTIMATED AT 1008 MB. THIS LOW PRES CENTER IS EMBEDDED WITHIN A RELATIVELY BROAD LOW LEVEL CYCLONIC CIRCULATION NEARLY 500 NM IN DIAMETER. CONVECTION HAS BEEN FLARING WITHIN 210 NM MAINLY W OF THE CENTER DURING THE PAST 12 TO 18 HOURS. HIGH RESOLUTION VISIBLE IMAGERY TODAY SHOWED A TRIO OF LLVL CLOUD SWIRLS ROTATING ABOUT ONE ANOTHER...WITH THE LAT/LONG POINT DEFINED ABOUT A CENTER POINT. GLOBAL MODEL GUIDANCE SUGGESTS THIS LOW WILL MOVE SLOWLY N THEN NW OVER THE NEXT FEW DAYS AND TOWARD AN ENVIRONMENT GENERALLY NOT FAVORABLE FOR INTENSIFICATION. THIS SYSTEM HAS A LOW POSSIBILITY OF BECOMING A TROPICAL CYCLONE OVER THE NEXT FEW DAYS. ...ITCZ/MONSOON TROUGH... MONSOON TROUGH EXTENDS FROM SW CARIBBEAN ACROSS THE COSTA RICA- NICARAGUA BORDER...ENTERING THE EPAC WATERS NEAR 11N86W TO 11N89W TO 13N92W WHERE IT REMAINS FRACTURED FROM THE REMAINDER OF THE TROUGH...THEN BEGINS ANEW NEAR 16N100W TO LOW PRES 1010 MB AT 20N111.5W TO LOW PRES 1007 MB AT 15.5N117.5W TO 13N123W TO LOW PRES 1009 MB AT 13.5N132.5W TO 10N140W. SCATTERED MODERATE TO STRONG CONVECTION NOTED FROM 05N TO 11N E OF 89W. SCATTERED MODERATE TO STRONG WITHIN 120 NM SW OF TROUGH BETWEEN 100W AND 107W. SCATTERED MODERATE TO STRONG FROM 06N TO 09.5N BETWEEN 125W AND 128W. ...DISCUSSION... AN UPPER ANTICYCLONE IS CENTERED AT 28N141W WITH A RIDGE EXTENDING NE WELL BEYOND 37N138W EVENTUALLY CRESTING OVER NW CANADA. ANOTHER UPPER ANTICYCLONE IS OVER S CENTRAL OLD MEXICO NEAR 20N99W WITH AN UPPER RIDGE EXTENDING W OVER THE PACIFIC TO NEAR 17N130W...AND RIDGING N-NW INTO NEW MEXICO. TWO CUTOFF UPPER CYCLONES STRADDLE THIS RIDGE INTO NEW MEXICO...WITH THE WESTERNMOST DEEP LAYERED CYCLONE JUST OFFSHORE OF SOUTHERN CALIFORNIA WITH TROUGH AXIS EXTENDING S-SW TO 22N125W THEN CONTINUING AS A WEAK MID LEVEL TROUGH AXIS SW TO 18N134W. THE MAIN CYCLONIC ENERGY OFF OF SRN CALIFORNIA IS FORECAST TO LIFT OUT TO THE NE AND AID IN THE RIDGE OVER MEXICO AMPLIFYING NWWD...WITH THE MEANDERING TROUGH TO THE SW STRETCHES FURTHER W. UPPER LEVEL NE TO E FLOW DOMINATES THE DEEP TROPICS TO THE S OF THESE FEATURES AND THE END RESULT OF THE ABOVE CHANGES WILL BE TO ALLOW UPPER LEVEL ELY'S TO EXTEND FURTHER W TO BEYOND 140W BY MON. LIGHT ELY VERTICAL WIND SHEAR OF LESS THAN 15 KT CONTINUES ACROSS THE DEEP TROPICS PER RECENT CIMSS/NESDIS ANALYSIS. A WEAK HIGH PRES RIDGE CONTINUES ACROSS W AND NW PORTIONS OF THE AREA TO NEAR 25N117W YIELDING NE TRADES AT LESS THAN 20 KT EXCEPT FOR THE FAR SW CORNER OF THE AREA FROM 11N TO 16N W OF 134W WHERE NE WINDS NEAR 20 KT ARE FOUND. S TO SW MONSOONAL FLOW INCREASED ACROSS S PORTIONS OF THE AREA BETWEEN 80W AND 95W EARLIER TODAY BUT HAVE SINCE DIMINISHED. PRECIPITABLE WATER IMAGERY TODAY SHOWED A PLUME OF DRY AIR EXTENDING SWD FROM THE GULF OF TEHUANTEPEC...VERIFYING NLY FLOW THROUGH THE PASS...BUT HAS SINCE DIMINISHED AS FLOW HAS SHIFTED MORE WESTERLY THERE. AS TROPICAL STORM NATE SHIFTS W OVER THE NEXT 24 HOURS NLY WINDS TO 20 KT WILL BEGIN TO AFFECT THE GULF OF TEHUANTEPEC BY SUNDAY EVENING. GULF OF CALIFORNIA...SOUTHERLY WINDS AT 15 TO 20 KT WILL CONTINUE OVER THE WATERS N OF 29N OVERNIGHT...THEN DIMINISH EARLY SUN. NORTHERLY SWELLS...RESULTING IN COMBINED SEAS OF 8 FT...HAVE MOVED INTO THE WATERS N OF 29N BETWEEN 120W AND 128W TODAY... AND WILL SPREAD AND W S TO ALONG 27N BETWEEN 122W AND 135W BY SUNDAY AFTERNOON. CROSS EQUATORIAL SOUTHERLY SWELL...WITH SEAS TO 9 FT... WILL MOVE N OVER THE WATERS S OF 10N BETWEEN 130W AND 93W SUNDAY. $$ STRIPLING