000 AXPZ20 KNHC 051000 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC FRI OCT 05 2012 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0930 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS W ACROSS THE SOUTHERN CARIBBEAN ALONG 10N FROM THE COLOMBIAN COAST TO ACROSS NORTHERN COSTA RICA TO 09N84W...THEN DIPS SW TO 06N98W WHERE IT ENDS. IT THEN RESUMES AT 14N107W THROUGH AN EMBEDDED LOW PRES AT 13N113W...AND CONTINUES SW TO 09N120W...W TO 10N128W...AND SW TO 07N138W WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO AN ITCZ WHICH CONTINUES SW TO BEYOND 06N140W. SCATTERED STRONG CONVECTION IS WITHIN 120 NM S OF TROUGH BETWEEN 81W-84W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120 NM S OF THE TROUGH BETWEEN 90W-92W ...WITHIN 30 NM OF TROUGH AT 08N121W...AND ALSO WITHIN 30 NM OF TROUGH BETWEEN 127W AND 129W. ...DISCUSSION... A BROAD UPPER LEVEL CYCLONE MOVING NE IS N OF THE DISCUSSION AREA NEAR 36N136W. A TROUGH STRETCHES SW FROM THIS LOW TO W OF THE AREA. WATER VAPOR IMAGERY AND UPPER MODEL GUIDANCE INDICATE THAT A NE TO SW JET STREAM BRANCH IS LOCATED NE TO SW OVER THE NW PORTION OF THE AREA WHERE SW WINDS OF 50-60 KT AS INDICATED BY SATELLITE-DERIVED UPPER DATA ARE ROUGHLY WITHIN 240 NM EITHER SIDE OF A LINE FROM 27N140W NE TO N OF THE AREA AT 32N127W AND THEN E TO ACROSS SOUTHERN CALIFORNIA...AND LESS IDENTIFIABLE OVER ARIZONA. ONLY SCATTERED THIN CIRRUS CLOUDS ARE NOTED WITHIN 75 NM OF THE JET STREAM. A SMALL UPPER CYCLONE PREVIOUSLY NOTED NEAR 19N130W HAS BECOME LESS DEFINED WITH TIME. BROAD HIGH PRES IN THE UPPER LEVELS DOMINATES THE AREA TO THE SE AND S OF THE JET STREAM BRANCH MENTIONED ABOVE TO NEAR 15N. THIS HIGH PRES AREA IS KEEPING THE ATMOSPHERE IN A RATHER STABLE STATE AS MODERATE TO STRONG SUBSIDENCE OVER THIS AREA SUPPRESSES CLOUDS FROM ACQUIRING ANY VERTICAL DEPTH...AS A RESULT ONLY PATCHES OF BROKEN TO SCATTERED STRATOCUMULUS CLOUDS MOVING W ARE SEEN FROM 16N TO 32N BETWEEN 121W AND 133W. WEAK UPPER DIFFLUENCE ALONG THE SOUTHERN PERIPHERY OF THE BROAD HIGH PRES AREA IS HELPING TO AID CONVECTION ALONG THE MONSOON TROUGH AS PREVIOUSLY DESCRIBED. THE DEBRIS MOISTURE FROM THE MONSOON TROUGH CONVECTION IS FANNING AWAY FROM IT BUT IS EVAPORATING BEFORE REACHING ALONG 17N. AN UPPER TROUGH EXTENDS SW ACROSS THE WESTERN GULF OF MEXICO AND OVER CENTRAL MEXICO TO A BASE IN THE EPAC AT 14N102W. A SECOND UPPER TROUGH EXTENDS SW ACROSS THE WESTERN CARIBBEAN TO ACROSS NORTHERN COSTA RICA. A BROAD UPPER RIDGE IN THE DEEP TROPICS IS PRESENT TO THE E OF 105W...BUT THERE ARE EMBEDDED SMALL UPPER CYCLONES OBSERVED WITHIN THE BROAD RIDGE. DENSE UPPER MOISTURE BEING ADVECTED WWD IS NOTED FROM 04N TO 11N E OF 96W. A 1009 MB SURFACE LOW IS ANALYZED ON THE SOUTHERN PERIPHERY OF THE RIDGE AT 13N113W WITH SCATTERED STRONG CONVECTION WITHIN 120 NM OF ITS CENTER IN THE N SEMICIRCLE. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 45 NM OF 12N107W. SOME OF THE DEBRIS MOISTURE FROM THIS CONVECTION CONTINUES TO STREAM NE ACROSS SE MEXICO AND THE EASTERN GULF OF MEXICO IN SWLY UPPER FLOW AHEAD OF THE UPPER TROUGH. ELSEWHERE AT THE LOW LEVELS...BROAD SURFACE RIDGING COVERS MUCH OF THE DISCUSSION AREA N OF 20N W OF 110W. SOUTHWESTERLY LOW LEVEL WINDS AT 15 TO 20 KT ALONG WITH CROSS EQUATORIAL SE TO S SWELLS CONTINUES TO RESULT IN AN AREA OF SEAS TO 8 FT IN THE AREA BOUNDED BY 03N TO 08N BETWEEN 110W AND 127W. THIS AREA WILL SHIFT SLIGHTLY N ON FRI...THEN WINDS WILL DIMINISH TO 15 KT AND SEAS WILL SUBSIDE TO LESS THAN 8 FT BY SAT NIGHT. IN THE MEANTIME...NW WINDS NE OF THE SURFACE RIDGE WILL INCREASE TO 20 TO 25 KT N OF ABOUT 28N AND E OF 117W TO THE COAST OF NORTHERN BAJA CALIFORNIA PENINSULA IN ABOUT 18 HRS AS A TIGHT PRES GRADIENT DEVELOPS BETWEEN THE RIDGING AND LOW PRES TROUGHING OVER THE NORTHERN GULF OF CALIFORNIA AND SW U.S. THESE WINDS ARE EXPECTED TO LAST OVER THE NEXT 48 HRS AND POSSIBLY BEYOND... HOWEVER THE AFFECTED AREA OF THESE WINDS SHOULD DIMINISH IN COVERAGE. THE INITIAL NORTHERLY SURGE OF 20 TO 25 KT THAT FILTERED THROUGH THE TEHUANTEPEC AREA IS STILL PROPAGATING W AND IS WITHIN THE AREA FROM 13N TO 17N BETWEEN 104W AND 113W AS CAPTURED BY THE HIGH RESOLUTION ASCAT PASS WITH VALID TIME 0512 UTC LAST NIGHT. THIS SWATH OF WINDS IS EXPECTED TO MERGE WITH THE INCREASING WINDS OVER THE NORTHERN SEMICIRCLE OF THE 1009 MB LOW AT 13N113W. THE LOW WILL MOVE WNW TO NEAR 14N116W BY LATE TONIGHT...AND TO NEAR 13N120W BY SAT FRI NIGHT WITH ITS WINDS MAINLY RESIDING IN THE NW QUADRANT. THE LOW SHOULD DEEPEN SLIGHTLY AS IT TRACKS WNW OVER THE NEXT COUPLE OF DAYS...HOWEVER BY SAT NIGHT IT IS EXPECTED TO BEGIN TO ENCOUNTER THE INITIAL STAGES OF COOLING SEA SURFACE TEMPERATURES (SSTS) ALONG WITH INCREASING UPPER LEVEL SW WINDS BOTH FACTORS ACTING TO HAMPER IT FROM STRENGTHENING BEYOND SAT NIGHT. GAP WINDS...N TO NE WINDS OF 20 TO 25 KT ARE EXPECTED TO PULSE ACROSS THE GULF OF TEHUANTEPEC THROUGH TONIGHT...THEN DIMINISH SAT AFTERNOON. THESE WINDS MAY MATERIALIZE AGAIN SAT NIGHT INTO SUN AT 20 TO 25 KT...BUT AGAIN IN PULSATING FASHION. $$ AGUIRRE