000 AXPZ20 KNHC 112155 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC THU JUN 11 2009 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2100 UTC. ...SPECIAL FEATURE... A 1009 MB SURFACE LOW IS LOCATED NEAR 13N119W MOVING NW 5 TO 10 KT. RECENT VISIBLE SATELLITE IMAGERY INDICATES THAT THIS POSITION IS ASSOCIATED WITH A CLOSED SURFACE CIRCULATION... THOUGH A WEAKER CIRCULATION IS NEAR 12N120W. A BROAD SURFACE TROUGH CONNECTS THESE TWO LOCATIONS. THE SATELLITE PRESENTATION OF THIS SYSTEM INDICATES THAT CONVECTION IS RATHER STRUNG OUT NEAR THIS TROUGH. ALSO...THE ENTRAINMENT OF DEEP LAYER DRY AIR IN NORTHWESTERLY FLOW ALOFT E OF AN UPPER ANTICYCLONE CENTERED NEAR 12N135W IS RESULTING IN A RATHER DISORGANIZED APPEARANCE TO DEEP CONVECTION NEAR THIS SYSTEM. NEVERTHELESS...SCATTERED MODERATE TO STRONG CONVECTION IS OCCURRING FROM 10N TO 14N BETWEEN 118W AND 123W. WINDS OF 20 TO 25 KT ARE OCCURRING WITHIN 120 NM OF THE LOW BASED ON RECENT SCATTEROMETER DATA. THIS SYSTEM IS FORECAST TO MOVE NORTHWESTWARD DURING THE NEXT FEW DAYS. IN RESPONSE...IT WILL ENCOUNTER INCREASED DEEP LAYER SHEAR AND DRY AIR ASSOCIATED WITH AN UPPER TROUGH OVER NORTHERN PORTIONS ALONG WITH COOLER SEA SURFACE TEMPERATURES OF THE DISCUSSION AREA. THESE FACTORS ARE FORECAST TO PROVIDE A MORE HOSTILE ENVIRONMENT FOR DEVELOPMENT WITH THIS SYSTEM. IN THE MEANTIME...THIS SYSTEM IS BEING MONITORED FOR TROPICAL CYCLONE FORMATION. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 91W EXTENDING SOUTHWARD FROM GUATEMALA MOVING W 15-20 KT. THIS WAVE LACKS ANY PARTICULARLY DISTINGUISHING FEATURES AS IT IS EMBEDDED WITHIN DEEP LAYER DRY AIR OVER THE EASTERN PORTION OF AN UPPER LEVEL ANTICYCLONE CENTERED OVER CENTRAL MEXICO. SUBSIDENCE IN DRY NORTHERLY FLOW IS PREVENTING THE DEVELOPMENT OF DEEP CONVECTION NEAR THIS WAVE...AND THIS WAVE IS BEING TRACKED EASTWARD BASED ON CONTINUITY. LOW LEVEL FLOW ACROSS THIS WAVE IS LIGHT AND VARIABLE BASED ON RECENT SCATTEROMETER DATA AND COMPUTER MODEL GUIDANCE. THIS WAVE WILL LIKELY BE DROPPED FOR THE 11/0000 UTC SURFACE ANALYSIS. ...ITCZ... AXIS IS ALONG 07N78W TO 09N90W TO 06N107W TO 09N116W TO 06N140W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 06N TO 10N BETWEEN 79W AND 89W. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 04N TO 09N BETWEEN 90W AND 106W. SCATTERED MODERATE CONVECTION IS FROM 05N TO 12N BETWEEN 107W AND 113W. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 09N TO 11N BETWEEN 124W AND 128W. ...DISCUSSION... N OF 20N... THE MAIN UPPER LEVEL FEATURES AT PRESENT INCLUDE AN UPPER LEVEL RIDGE N OF 25N W OF 137W...AN UPPER LEVEL TROUGH N OF 20N BETWEEN 114W AND 137W...AND AN UPPER LEVEL ANTICYCLONE CENTERED OVER CENTRAL MEXICO WITH AN UPPER RIDGE PROTRUDING WESTWARD INTO THE EAST PACIFIC REGION. DEEP SUBSIDENCE EAST OF THE FIRST RIDGE IS SUPPORTING A 1024 MB SURFACE HIGH NEAR 30N143W WITH A SURFACE RIDGE EXTENDING EASTWARD ACROSS THE NORTHERN WATERS. THE PRESSURE GRADIENT AT THE SOUTHERN PERIPHERY OF THIS RIDGE WILL DRIVE NORTHEASTERLY TRADE WINDS OF 15 TO 20 KT GENERALLY IN AN AREA FROM 10N TO 20N W OF AROUND 120W DURING THE NEXT COUPLE DAYS WITH THE SURFACE RIDGE PERSISTING ACROSS THE NORTHERN WATERS. ADDITIONALLY...A STRENGTHENING SURFACE TROUGH OVER MEXICO WILL STEEPEN THE PRESSURE GRADIENT OFF THE S AND W COASTS OF BAJA CALIFORNIA...WHERE NW WINDS TO 20 KT WILL OCCUR. THESE WINDS WILL INCREASE TO 20 TO 25 KT ON SATURDAY WHEN BROAD SYNOPTIC SCALE LIFT STRENGTHENS THE SURFACE TROUGH OVER MEXICO IN RESPONSE TO THE AFOREMENTIONED UPPER TROUGH BEING EJECTED EASTWARD OVER THE SW UNITED STATES AND NORTHWESTERN MEXICO. ADDITIONALLY...THIS ASCENT IS FORECAST TO SUPPORTING WEAK SMALLER SCALE SURFACE LOWS IN THE NORTHERN GULF OF CALIFORNIA DURING THE NEXT FEW DAYS...WHICH WILL BE ENHANCED AT NIGHT WHEN NOCTURNAL DRAINAGE FLOW IS MAXIMIZED. UPPER LEVEL JET MAXIMA ROUNDING THE BASE OF THE UPPER LEVEL TROUGH WILL CONTRIBUTE TO ENHANCED DOWNSLOPE FLOW INTO THE NORTHERN GULF OF CALIFORNIA...FURTHER SUSTAINING THE SURFACE LOWS AND CORRESPONDING THREAT FOR SW TO W WINDS OF 20 TO 25 KT ACROSS THE N GULF OF CALIFORNIA. THE HIGH RESOLUTION QUIKSCAT PASS AROUND 11/1300 UTC CONFIRMED THE PRESENCE OF THESE WINDS IN THE N GULF OF CALIFORNIA. HIGHER RESOLUTION MODEL GUIDANCE INDICATES THESE WINDS CONTINUING DURING THE NEXT FEW DAYS. S OF 20N... AN AREA OF LOW PRESSURE IS CURRENTLY BEING MONITORED FOR TROPICAL CYCLONE FORMATION PRESENTLY NEAR 13N119W...WHICH IS DISCUSSED IN THE SPECIAL FEATURES SECTION ABOVE. ELSEWHERE...GENERALLY LIGHT WINDS ARE OCCURRING OUTSIDE OF CONVECTION ASSOCIATED WITH THE ITCZ. HOWEVER...S TO SW SWELL ASSOCIATED WITH WAVE HEIGHTS OF 8 TO 13 FT WILL CONTINUE TO OVERTAKE SOUTHERN PORTIONS OF THE DISCUSSION AREA DURING THE NEXT FEW DAYS. HOWEVER...MAXIMUM SEAS WILL DECREASE AS THESE WAVES DEPART THEIR GENERATION FROM PREVIOUS SOUTHERN HEMISPHERIC STORMS. THESE WAVES WILL AFFECT THE COAST OF CENTRAL AMERICA SAT AND SUN...WHERE LARGE AND DANGEROUS BREAKING SURF CONDITIONS ARE EXPECTED ALONG THE COASTS. $$ COHEN