000 AXPZ20 KNHC 171548 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC WED JUN 17 2009 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1515 UTC. ...SPECIAL FEATURE... A 1008 MB LOW PRES CENTER LOCATED NEAR 15N106W...OR ABOUT 300 MILES SW OF MANZANILLO MEXICO MOVING WNW AT 5 KT. ALTHOUGH CONVECTION HAS INCREASED IN THE PRE-DAWN HOURS...THIS SYSTEM REMAINS SOMEWHAT DISORGANIZED WITH MULTIPLE LOW LEVEL CENTERS NOTED ALONG AN ELONGATED NE TO SW ORIENTED TROUGH. SCATTEROMETER DATA SHOW MODERATE TO FRESH S TO SW WINDS SOUTH OF THIS FEATURE...ENHANCING LOW LEVEL CONVERGENCE ENHANCE CONVECTION NEAR THE CENTER. EARLIER SCATTEROMETER DATA SUGGESTED THAT THERE WERE SW WINDS UP TO 25 KT ON THE SE SIDE OF THE LOW. LIGHT TO MODERATE N TO NE WINDS ARE NOTED NW OF THE LOW. THIS SYSTEM HAS THE POTENTIAL TO BECOME A TROPICAL DEPRESSION DURING THE NEXT DAY OR TWO AS IT MOVES SLOWLY WEST-NORTHWESTWARD. THERE IS A HIGH CHANCE...GREATER THAN 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 06N77W TO 07N90W TO 12N107W TO 07N123W TO 06N140W. SCATTERED MODERATE TO STRONG CONVECTION WITHIN 120 NM N OF AXIS E OF 80W IN THE GULF OF PANAMA. SCATTERED MODERATE CONVECTION WITHIN 90 NM S OF AXIS BETWEEN 95W AND 98W. SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN 150 NM S OF AXIS BETWEEN 105W AND 115W. SCATTERED MODERATE CONVECTION WITHIN 90 NM EITHER SIDE OF AXIS W OF 125W. ...DISCUSSION... A REX BLOCK PATTERN DOMINATES THE DISCUSSION AREA W OF 125W WITH AN UPPER RIDGE IS CENTERED N OF 31N135W...N OF AN UPPER LOW CENTERED NEAR 15N137W. NORTHERLY FLOW ON THE EAST SIDE OF THE UPPER RIDGE IS AMPLIFYING A MID TO UPPER LEVEL TROUGH EXTENDING FROM NORTHERN BAJA TO 20N125W. STRONG JET ENERGY N OF THE AREA FLATTENS THE UPPER RIDGE AND CUTS OFF THE UPPER LOW OVER NORTHERN BAJA BY THU. THE IMPACT AT THE SURFACE OF ALL THIS IS THAT THE SURFACE RIDGE WILL PERSIST FROM A 1026 MB SURFACE HIGH NE OF HAWAII TO THE BAJA COAST. EARLIER SCATTEROMETER DATA SHOWED A SWATH OF FRESH TRADES PERSISTING S OF THE RIDGE FROM ROUGHLY 10N TO 20N. THE SURFACE HIGH WILL SHIFT NORTHWARD THROUGH FRI...ALLOWING THE SWATH OF TRADE WINDS TO SHIFT NORTH ACCORDINGLY. A SMALL AREA OF MODERATE TO FRESH NORTHERLY WINDS WAS INDICATED ON A 04Z ASCAT PASS BETWEEN THE PERIPHERY OF THE RIDGE AXIS AND THE CENTRAL BAJA COAST. THIS AREA WILL PERSIST OFF AND ON THROUGH THE NEXT COUPLE OF DAYS WITH THE SURFACE RIDGE PERSISTING. THE 04Z ASCAT PASS ALSO SHOWED 15 TO 20 KT SOUTH TO SOUTHWEST FLOW CONVERGING INTO THE ITCZ BETWEEN 105W AND 115W...SUPPORTING ALONG MODERATE TO STRONG CONVECTION ITCZ. FURTHER EAST...A WEAK SURFACE TROUGH MIGRATING WESTWARD THROUGH GUATEMALA AND SOUTHERN MEXICO HAS BEEN INTERACTING WITH DRAINAGE FLOW CONVERGENCE AND UPPER LEVEL DIVERGENCE TO SPARK A STRONG CLUSTER OF CONVECTION IN THE GULF OF TEHUANTEPEC. THIS SHOULD DIMINISH THROUGH THE DAY...ALTHOUGH RESIDUAL CONVECTION WILL REMAIN WITH THE TROUGH THROUGH THE NEXT 48 HOUR AS IT SHIFTS WEST ALONG THE MEXICAN COAST. EAST OF THE TROUGH...A TROPICAL WAVE CURRENTLY OVER EL SALVADOR WILL TRAIL BEHIND THE TROUGH...POSSIBLY INCREASING EARLY MORNING CONVECTION ALONG THE GUATEMALAN AND SOUTHERN MEXICAN COASTS. $$ CHRISTENSEN