000 AXPZ20 KNHC 010931 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC MON JUN 01 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 0900 UTC. ...ITCZ... AXIS ALONG 09N78W TO 10N95W TO 08N105W TO 07N120W TO 07N140W. SCATTERED MODERATE CONVECTION IS FROM 06N TO 08N BETWEEN 79W AND 82W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 06N TO 09N BETWEEN 89W AND 92W. SCATTERED MODERATE CONVECTION IS FROM 09N TO 13N BETWEEN 98W AND 110W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM OF 06N117W. SCATTERED MODERATE CONVECTION IS FROM 10N TO 14N BETWEEN 121W AND 127W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 07N TO 16N BETWEEN 130W AND 139W. ...DISCUSSION... N OF 20N... A DEEP CLOSED LOW N OF THE AREA IS ASSOCIATED WITH AN OCCLUDED 1008 MB SURFACE LOW NEAR 38N134W. AN ASSOCIATED WEAKENING STATIONARY FRONT EXTENDS ACROSS THE NW WATERS FROM 30N130W TO 24N140W. THIS FRONT CONTINUES TO LOSE UPPER SUPPORT AS THE ATTENDANT UPPER LOW IS CUT OFF FROM ANY SUBSTANTIAL UPPER JET MAXIMA. THUS...THE PRESSURE GRADIENT AROUND THE FRONT HAS SUBSTANTIALLY WEAKENED...AND THE QUIKSCAT PASS AROUND 01/0300 UTC CONFIRMS THAT WINDS W OF THE FRONT HAVE FALLEN TO THE 10-15 KT RANGE. SEAS IN NW SWELL ASSOCIATED WITH THIS FRONT HAVE SUBSIDED BELOW 8 FT AS THEIR SUPPORTING WIND FIELD HAS SINCE DIMINISHED. AN UPPER LEVEL TROUGH ASSOCIATED WITH THE AFOREMENTIONED DEEP LOW EXTENDS OVER THE NORTHERN WATERS WITH AN AXIS FROM 30N128W TO 23N126W. ATMOSPHERIC INSTABILITY WITH THE UPPER TROUGH IS CURRENTLY SUPPORTING SCATTERED SHOWERS N OF 27N BETWEEN 120W AND 126W. DURING THE NEXT FEW DAYS...THE UPPER TROUGH IS FORECAST TO PIVOT CYCLONICALLY AROUND ITS PARENT DEEP LOW N OF THE AREA. SOUTHWESTERLY FLOW ALOFT E OF THE UPPER TROUGH WILL BECOME INCREASINGLY DIFFLUENT DURING THE NEXT DAY...WHICH WILL DRIVE INCREASING SURFACE PRESSURE FALLS OVER N MEXICO AND THE N GULF OF CALIFORNIA. REGIONAL AND GLOBAL MODEL GUIDANCE INDICATES THAT A WEAK...SMALL-SCALE SURFACE LOW WILL LIKELY FORM IN THE NORTHERN GULF OF CALIFORNIA TONIGHT...AS WELL AS THE NEXT SEVERAL NIGHTS. THE CORRESPONDING PRESSURE GRADIENT WILL INCREASE SW WINDS ACROSS THE N GULF OF CALIFORNIA TONIGHT...WHICH WILL INTERACT WITH DOWNSLOPE FLOW OFF THE BAJA CALIFORNIA COAST TO SUPPORT SW WINDS OF 20 TO 25 KT TONIGHT. A SIMILAR SITUATION WILL OCCUR TUE NIGHT OVER THE N GULF OF CALIFORNIA...WITH SW FLOW ALOFT CONTINUING OVER THE N GULF OF CALIFORNIA AS THE AFOREMENTIONED UPPER LOW DRIFTS SOUTHEASTWARD TOWARD THE WESTERN UNITED STATES COAST. THE STRONGEST WINDS OVER THE NORTHERN GULF OF CALIFORNIA ARE FORECAST TO OCCUR WED NIGHT AND THU NIGHT...WHEN THE UPPER LEVEL HEIGHT GRADIENT AT THE SOUTHERN PERIPHERY OF THE UPPER LEVEL CYCLONE TIGHTENS... YIELDING A 100-110-KT UPPER LEVEL JET MAX S OF THE UPPER LOW... ENHANCING THE DOWNSLOPE FLOW INTO THE N GULF OF CALIFORNIA. THE STRONGEST DOWNSLOPE WINDS ARE EXPECTED AT NIGHT WHEN NOCTURNAL DRAINING FLOW IS MAXIMIZED. THE SURFACE PRESSURE GRADIENT BETWEEN PERSISTENT SURFACE TROUGHING OVER MEXICO AND WEAK SURFACE RIDGING OVER THE E PACIFIC WILL CONTINUE DRIVING NW WINDS AROUND 20 KT NEAR THE S AND W COASTS OF BAJA CALIFORNIA. THESE CONDITIONS ARE EVIDENT IN THE QUIKSCAT PASS AROUND 01/0130 UTC AND THE ASCAT PASS AROUND 01/0500 UTC. THE PROLONGED DURATION OF THESE WINDS WILL LIKELY INCREASE SEAS TO 8 FT LOCALLY. S OF 20N... A SURFACE TROUGH EXTENDS FROM 14N96W TO A 1009 MB LOW NEAR 09N100W TO 07N102W. LOW LEVEL CONVERGENCE NEAR THESE FEATURES IS RESULTING IN SCATTERED MODERATE CONVECTION FROM 09N TO 13N BETWEEN 98W AND 110W. THIS CONVECTION IS ALSO BEING SUPPORTED BY UPPER LEVEL DIVERGENCE AND DEEP LAYER MOISTURE NEAR AN UPPER LEVEL RIDGE S OF 15N E OF 103W. HOWEVER...WESTERLY FLOW ALOFT W OF THE RIDGE APPEARS TO BE ADVECTING DRY AIR TOWARD THIS SYSTEM...WITH CONVECTION SHOWING OVERALL SIGNS OF DECREASING IN AREAL COVERAGE AN INTENSITY BASED ON RECENT SATELLITE IMAGERY. THE LOW IS FORECAST TO REMAIN RATHER WEAK DURING THE NEXT FEW DAYS AS UPPER LEVEL DRY AIR IS ENTRAINED INTO THE SYSTEM. GLOBAL AND STATISTICAL MODELS FEATURE A RATHER WIDE ARRAY OF SOLUTIONS WITH REGARD TO THE TRACK OF THE LOW. HOWEVER...THE GFS PROVIDES THE FAVORED SOLUTION...WITH A GENERAL WESTWARD TRACK. NORTHWARD DEVIATIONS WOULD BE PROHIBITED BY STRONGER WESTERLY SHEAR AND DRY AIR N OF THE CURRENT SYSTEM PROVIDING HOSTILE CONDITIONS FOR CONVECTIVE ORGANIZATION. DEVELOPMENT OF THIS SYSTEM...IF ANY...IS EXPECTED TO BE SLOW TO OCCUR. FARTHER TO THE W...UPPER LEVEL DIFFLUENCE IN MOIST SOUTHWESTERLY FLOW ALOFT IS GENERATING SCATTERED MODERATE AND ISOLATED STRONG CONVECTION FROM 07N TO 16N BETWEEN 130W AND 139W. THIS ACTIVITY IS BEING ENHANCED BY LOW LEVEL CONVERGENCE NEAR A SURFACE TROUGH THAT EXTENDS FROM 13N133W TO 10N137W TO 08N137W. THE PRESSURE GRADIENT N OF THE TROUGH IS ENHANCING AN AREA OF NE TO E TRADE WINDS AROUND 20 KT FROM 10N TO 17N W OF 125W BASED ON THE QUIKSCAT PASS AROUND 01/0300 UTC. THESE TRADES WINDS ARE FORECAST TO PERSIST IN THE SAME GENERAL AREA WITH NEARLY THE SAME INTENSITY WITH SURFACE RIDGING FARTHER TO THE N. ENHANCED EASTERLY TRADE WINDS IN THE CARIBBEAN ARE FORECAST TO BLEED INTO THE GULF OF PAPAGAYO TUE NIGHT INTO WED NIGHT...WHEN NE TO E WINDS OF 20 KT ARE EXPECTED FROM 10N TO 12N E OF 90W INCLUDING THE GULF OF PAPAGAYO. $$ COHEN