000 AXPZ20 KNHC 302150 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC THU JUL 30 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 2145 UTC. ...SPECIAL FEATURE... RECENTLY UPGRADED TROPICAL STORM LANA CENTERED NEAR 12.3N141.4W OR 910 NM EAST-SOUTHEAST OF HILO HAWAII AT 2100 UTC MOVING WEST AT 16 KT WITH MAXIMUM SUSTAINED WINDS OF 35 KT WITH GUSTS TO 45 KT HAS MOVED WEST OF THE DISCUSSION AREA. SEE LATEST PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS HFOTCPCP1/WTPA21 FOR MORE DETAILS. FURTHER INFORMATION ON THIS SYSTEM WILL BE CARRIED IN THE HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE UNDER AWIPS/WMO HEADERS HFOSIMHI/ATHW40 PHFO ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 96W N OF 05N MOVING W NEAR 20 KT OVER THE PAST 24 HOURS. LOW LEVEL MOISTURE CONVERGENCE NEAR THE TROPICAL WAVE COUPLED WITH BROAD UPPER LEVEL DIFFLUENCE BETWEEN AN INVERTED TROUGH TO THE SW OF THE WAVE AND AN UPPER LEVEL RIDGE AXIS TO ITS N IS SUPPORTING SCATTERED MODERATE CONVECTION WITHIN 270 NM W OF THE TROPICAL WAVE AXIS FROM 08N TO 14N. MID LEVEL CYCLONIC TURNING WAS NOTED WITHIN THE CONVECTIVE AREA. TROPICAL WAVE IS ALONG 120W FROM 06N TO 17N MOVING W NEAR 10 KT OVER THE PAST 24 HOURS. SCATTERED MODERATE ISOLATED STRONG CONVECTION WAS NOTED WITHIN 240 NM W OF THE WAVE AXIS FROM 09N TO 13N...AND AT THE NORTHERN END OF THE WAVE WITHIN 60 NM OF 16N119W. THIS CONVECTION LIES IN THE UPPER LEVEL DIFFLUENT REGION ON THE EASTERN SIDE OF AN UPPER LEVEL LOW NEAR 14N126W. ...ITCZ... THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...08N82W TO 09N95W TO 07N105W TO 12N120W TO 10N140W. SCATTERED MODERATE ISOLATED STRONG WITHIN 120 NM N AND 180 NM S OF AXIS BETWEEN 115W AND 130W...AND WITHIN 150 NM EITHER SIDE OF THE AXIS E OF 92W. SCATTERED MODERATE FROM 08N TO 14N BETWEEN 97W AND 104W. ...DISCUSSION... A LOW TO MID LEVEL CIRCULATION WAS EVIDENT IN VISIBLE AND INFRARED SATELLITE IMAGERY NEAR 08N81W WILL MOVE WESTWARD OVER THE NEXT 48 HOURS AND SLOWLY DEVELOP AS IT TRACKS ALONG WITH A REGION OF MODERATE UPPER LEVEL DIFFLUENCE. CURRENTLY...THE MAJORITY OF THE CONVECTION IN THE EASTERN PACIFIC ASSOCIATED WITH THE SYSTEM LIES WITHIN 150 NM EITHER SIDE OF THE ITCZ AXIS E OF 92W WITH SCATTERED MODERATE CONVECTION EXTENDING THROUGH PANAMA INTO THE SW CARIBBEAN. AS THIS LOW MOVES W OVER THE NEXT TWO DAYS...EXPECT THE LOW LEVEL VORTICITY TO BE ENHANCED AS IT ENCOUNTERS THE CROSS EQUATORIAL SOUTHERLY FLOW IN THE FAR EASTERN PACIFIC AND THE EASTERLY GAP WINDS FROM PAPAGAYO. SEE THE DISCUSSION ON GAP WINDS BELOW FOR DETAILS ON THE GULF OF PAPAGAYO WINDS. THE NEXT ROUND OF SOUTHWESTERLY SWELL WILL BE CROSSING THE EQUATOR OVER THE NEXT 24 HOURS. SIGNIFICANT WAVE HEIGHTS ARE ALREADY AROUND 8 FT IN SE SWELL S OF 08N BETWEEN 116W AND 126W. THE SW SWELL MOVES INTO THE REGION LATE TODAY WITH LONGER PERIOD SW SWELL ENCROACHING ON THIS GENERAL REGION IN THE S CENTRAL PORTION OF THE FORECAST AREA ON SAT. THIS ROUND OF SWELLS IS NOT EXPECTED TO HAVE THE IMPACT OF THE SWELL EVENT LAST WEEKEND. SURFACE HIGH PRESSURE AND GENERALLY SUBSIDENT CONDITIONS WITH WIDESPREAD STRATOCUMULUS CLOUDS DOMINATES THE REGION N OF 20N W OF 120N AND FROM 20N120W TO THE CENTRAL BAJA CALIFORNIA COAST. GAP WINDS... THE HIGH RESOLUTION QUIKSCAT PASS FROM 1356 UTC AND A SUBSEQUENT ASCAT PASS INDICATED SE WINDS IN THE NORTHERN GULF OF CALIFORNIA OF 20-25 KT. THIS FLOW APPEARS TO BE DRIVEN BY THE TIGHTENED PRESSURE GRADIENT BETWEEN LOW PRESSURE OVER INTERIOR SOUTHERN CALIFORNIA AND HIGH PRESSURE OVER NW MEXICO. THIS PRESSURE GRADIENT IS STRONGEST WITH AFTERNOON HEATING. MODEL GUIDANCE SHOWS THIS PRESSURE GRADIENT WEAKENING OVER THE NEXT 24 HOURS...ALLOWING THESE WINDS TO DIMINISH BELOW 20 KT BY FRI MORNING. THE 1210 UTC HIGH RESOLUTION QUIKSCAT PASS SHOWED NE TO E WINDS IN THE 20 TO 25 KT RANGE DOWNWIND OF THE GULF OF PAPAGAYO. THESE WINDS ARE EXPECTED TO MODERATE ALONG WITH THE TRADE WIND FLOW IN THE SW CARIBBEAN OVER THE NEXT 24 HOURS...BUT AS THE LOW PRES SYSTEM NEAR PANAMA PUSHES WEST OF THE GULF OF PAPAGAYO ON SATURDAY EXPECT THE WINDS TO TRACK EAST AWAY FROM THE GULF AND THE FLOW ASSOCIATED WITH THE LOW TO INCREASE TO 20 KT ON ITS NORTHERN SIDE. $$ COBB