000 AXPZ20 KNHC 112233 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC WED SEP 11 2013 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2100 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... MONSOON TROUGH AXIS CONTINUES ACROSS PORTIONS OF CENTRAL AMERICA FROM 13.5N86W TO 14N97W TO 13.5N108W TO LOW PRES NEAR 11.5N113.5W 1010 MB TO LOW PRES NEAR 11.5N123.5W 1010 MB TO 10N133W...WHERE IT TRANSITIONS TO ITCZ...CONTINUING ON BEYOND 09N140W. SCATTERED MODERATE CONVECTION NOTED FROM 05N TO 08N BETWEEN 81W AND 86.5W. SCATTERED MODERATE TO STRONG CONVECTION NOTED WITHIN 150 NM EITHER SIDE OF LINE FROM 10N107W TO 10.5N100W TO 15N94. SCATTERED MODERATE TO STRONG CONVECTION NOTED N OF 11.5N BETWEEN 87W AND 91.5W. SCATTERED MODERATE ISOLATED STRONG CONVECTION NOTED WITHIN 150 NM SW OF TROUGH FROM 21N109W TO 18.5N108W TO 16.5N104.5W. ...DISCUSSION... AN ELONGATED TILT UPPER TROUGH IS BRUSHING ACROSS THE FAR NW PORTION OF THE DISCUSSION AREA FROM 33N141W TO 25N147W...WITH EMBEDDED SHORT WAVE ENERGY LIFTING NE WITH TIME...AND IS EXPECTED TO PUSH A WEAK SURFACE COLD FRONT INTO THE NW CORNER AT MIDDAY THU. THE FRONT WILL MOVE SLOWLY SE ON FRI...STALLING AND WASHING OUT FROM 32N133W TO 27N140W ON SAT. EXPECTING ONLY A 10 KT WIND SHIFT ALONG THE FRONTAL BOUNDARY WITH SEAS 4-6 FT PRIMARILY DUE TO NW SWELL. AN UPPER CYCLONE IS QUASI-STATIONARY OVER THE BORDER OF CALIFORNIA AND ARIZONA AT 35N115W...TRAILING AN UPPER TROUGH SE ACROSS THE BAJA CALIFORNIA PENINSULA TO 27N111.5W. UPPER MOISTURE IS NOTED ONLY OVER THE NORTHERN SEMICIRCLE OF THIS CYCLONE TODAY. UPPER LEVEL RIDGING GENERALLY PREVAILS S AND SE OF THESE TWO FEATURES...CENTERED ON AN UPPER ANTICYCLONE OVER MEXICO NEAR 25.5N105W EXTENDING SW TO 18N122W THEN W-SW TO 17N137W AND THEN SW TO S OF HAWAIIAN ISLANDS. A WEAK RIDGE EXTENDS SE FROM THE PARENT HIGH ACROSS SE MEXICO...WHILE A N TO S ALIGNED DEEP LAYERED TROUGH IS ACROSS THE W GULF OF MEXICO AND INTO THE BAY OF CAMPECHE...AND SEPARATES A SECOND DEVELOPING UPPER ANTICYCLONE ACROSS THE NW CARIBBEAN. ABUNDANT TROPICAL MOISTURE CONTINUES TO CONVERGE ACROSS CENTRAL AMERICA AND SE MEXICO FROM 04N TO 20N E OF 100W...AND IS MAINTAINING A VERY UNSTABLE LOWER ATMOSPHERE. WIDESPREAD CLUSTERS OF CONVECTION ARE DESCRIBED ABOVE AND ALSO OCCURRING OVER LAND ACROSS CENTRAL AMERICA...AND ARE AIDING IN MAINTAINING UPPER DIVERGENCE AND ANTICYCLONIC OUTFLOW ACROSS THIS REGION. GLOBAL MODELS SUGGEST THESE FAVORABLE UPPER LEVEL CONDITIONS WILL GRADUALLY BECOME LESS FAVORABLE ON FRIDAY. AT THE LOW LEVELS A 1018 MB SURFACE HIGH IS CENTERED NEAR 25N128W WITH ITS ANTICYCLONIC ENVELOPE DOMINATING THE AREA N OF 18N W OF 115W. A LOW LEVEL TROUGH ORIENTED FROM NNW TO SSE CONTINUES FROM THE SOUTHERN GULF OF CALIFORNIA TO A BASE NEAR 17.5N104W. CONVECTION OCCURRING TO THE W OF THIS TROUGH IS DESCRIBED ABOVE. IS OBSERVED FROM 15-23N E OF 109W TO ABOUT 90 NM INLAND MEXICO. THIS TROUGH IS EXPECTED TO PERSIST FOR SEVERAL DAYS AND MAY GRADUALLY MERGE WITH MONSOON TROUGH PRESENTLY OFFSHORE OF MEXICO...WITH WEAK SURFACE LOWS FORECAST BY GLOBAL MODELS TO FORM INTERMITTENTLY ALONG THE SOUTHERN EXTENT OF THE TROUGH. SOUTHWESTERLY MONSOONAL FLOW AT 15-20 KT IS OBSERVED MOSTLY BY SCATTEROMETER DATA ACROSS THE TROPICS ROUGHLY FROM 05N TO 11N E OF 116W...WITH A FEW REGIONS OF 20-25 KT WINDS...AND SEAS TO 9 AND 10 FT. ONE SUCH AREA WAS FROM 07N TO 11N BETWEEN 97W AND 106W...WHILE A SECOND WAS FROM 10N TO 14N BETWEEN 88W AND 91W. A DISORGANIZED WEATHER SYSTEM SHIFTING W ACROSS THE YUCATAN PENINSULA DURING THE NEXT 24 HOURS WILL BEGIN TO FEED MOISTURE FROM ENHANCED SW MONSOON FLOW ACROSS A BROADENING AREA...AND THROUGH THE GULF OF TEHUANTEPEC...CONTINUING INTO FRI. SEAS ACROSS THIS AREA ARE EXPECTED TO REMAIN 7-10 FT INTO FRI. ELSEWHERE...LONG PERIOD SOUTHERN HEMI SWELL IS MOVING THROUGH THE REGION E OF 110W THIS AFTERNOON AND WILL REACH THE CENTRAL AMERICAN AND MEXICAN COASTLINES THIS EVENING AND TONIGHT WITH STRONG BUT MODERATE SURF. $$ STRIPLING