000 AXNT20 KNHC 121742 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SUN AUG 12 2007 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS... WEATHER OBSERVATIONS...AND RADAR. BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...SPECIAL FEATURE... A 1008 MB LOW...ASSOCIATED WITH A VIGOROUS TROPICAL WAVE...IS LOCATED OVER THE FAR EASTERN ATLANTIC OCEAN ABOUT 150 NM SOUTH OF THE SOUTHERNMOST CAPE VERDE ISLANDS NEAR 12.5N25W. VISIBLE IMAGERY SHOWS THE LOW-LEVEL CIRCULATION PARTIALLY EXPOSED TO THE E OF A CONVECTIVE MASS FROM 10N-14N BETWEEN 25W-30W. OVERALL...THIS SYSTEM HAS IMPROVED IN ORGANIZATION OVER THE PAST 24 HOURS AND A TROPICAL DEPRESSION COULD FORM LATER TODAY OR TOMORROW AS THE LOW MOVES WESTWARD AT 15-20 KT. . ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 35W/36W S OF 14N MOVING W 10-15 KT. A SMALL LOW-LEVEL CLOUD SWIRL HAS DEVELOPED...OR PULLED OUT OF THE ITCZ CONVECTION...LIKELY ASSOCIATED WITH THIS FEATURE. THE UW-CIMSS TPW PRODUCT DOES NOT SHOW MUCH OF A MOISTURE SURGE BUT IT'S NOT SURPRISING GIVEN THE WAVE'S LOW AMPLITUDE AND CLOSE PROXIMITY TO THE MUCH LARGER WAVE/LOW (SPECIAL FEATURE) TO THE E. TROPICAL WAVE IS RELOCATED E ALONG 43W S OF 14N MOVING W NEAR 10 KT. THIS RELOCATION IS BASED ON THE IMPROVED SATELLITE SIGNATURE WHICH SHOWS AN INVERTED V-SHAPE TO IT'S CLOUD FIELD AND THE SURROUNDING STRATOCUMULUS. MID-LEVEL ROTATION HAS ALSO BECOME EVIDENT ALONG THE AXIS WITHIN THE ITCZ. AT FIRST...IT WAS THOUGHT THAT THIS COULD HAVE BEEN A MISSED FEATURE RATHER THAN THE WAVE ALREADY ON THE ANALYSIS...BUT FURTHER INVESTIGATION SUGGESTS OTHERWISE. MET-9 SATELLITE HOVMOLLER DIAGRAMS DISPLAY A TRACEABLE SLOW MOVING FEATURE LIKELY ASSOCIATED WITH THIS WAVE. IN ADDITION...THE UW-CIMSS TPW PRODUCT INDICATES A SLOW MOVING SLIGHT MOISTURE RIDGE WHICH MATCHES UP WELL WITH THE HOVMOLLER DIAGRAMS. SCATTRED SHOWERS AND ISOLATED TSTMS ARE CURRENTLY CONFINED NEAR THE INTERSECTION OF THE ITCZ FROM 7N-11N BETWEEN 39W-45W. TROPICAL WAVE IS IN THE CENTRAL/WRN CARIB ALONG 76W/77W S OF 23N. EARLIER SATELLITE IMAGERY WAS NOT MUCH HELP IN FINDING THE LOCATION OF THE WAVE WITH ABUNDANT CIRRUS MASKING THE LOWER LEVEL CLOUDS. THE TOOL MOST RELIED ON IS THE UW-CIMSS TPW PRODUCT WHICH CLEARLY SHOWS A WWD MOVING SHARP MOISTURE GRADIENT...OR SURGE. ALTHOUGH MOST OF THE DRYING IS ASSOCIATED WITH NLY FLOW ON THE W SIDE OF AN UPPER LOW OVER THE ERN CARIB WATERS...PART OF IT MAY BE RELATED TO THIS THIS WAVE AS IT HAS HAD A SURGE-LIKE HISTORY. THE INTERACTION BETWEEN THIS WAVE AND THE UPPER LOW NEAR THE FLORIDA KEYS IS PRODUCING SCATTERED SHOWERS AND TSTMS ACROSS A GOOD PORTION OF THE W CARIB AND IN THE BAHAMAS. DEVELOPMENT OF THIS SYSTEM...IF ANY...IS EXPECTED TO BE SLOW TO OCCUR AS THE NRN PORTION MOVES NW TOWARD THE SOUTHERN GULF OF MEXICO AT 5-10 KT. TROPICAL WAVE IS ALONG 86W/87W S OF 22N MOVING W NEAR 15 KT. THIS WAVE IS EMBEDDED IN A MOIST UPPER ENVIRONMENT WHICH IS HELPING TO SUSTAIN SCATTERED MODERATE CONVECTION WITHIN 240 NM EITHER SIDE OF THE WAVE AXIS. ...THE ITCZ... THE ITCZ AXIS IS CENTERED ALONG 16N17W 11N26W 9N35W 10N42W 10N61W. BESIDES THE CONVECTION DISCUSSED ABOVE...ISOLATED MODERATE IS ALONG THE AFRICAN COAST FROM 12N-16N E OF 18W ASSOCIATED WITH THE NEXT TROPICAL WAVE. DISCUSSION... GULF OF MEXICO... AN UPPER LOW SPINNING NEAR THE LOWER FLORIDA KEYS IS PRODUCING AN AREA OF CLOUDINESS AND SCATTERED SHOWERS/TSTMS ACROSS THE SRN GULF...ESPECIALLY NEAR THE UPPER LOW CENTER. MUCH DEEPER MOISTURE IS FURTHER S IN THE NW CARIB WHERE A TROPICAL WAVE IS ADDING A LIFTING MECHANISM. THIS UPPER FEATURE DOES HAVE A WEAK ILL-DEFINED SFC TROUGH ANALYZED FROM 24N86W 28N84W. THIS TROUGH ALONG WITH ANOTHER LOW-LEVEL BOUNDARY ACROSS THE N GULF COAST IS KEEPING A VERY WEAK PRES GRADIENT IN THE REGION WHICH HAS ALLOWED WINDS TO BE LIGHT AND SOMEWHAT VARIABLE. DRIER CONDITIONS ARE OBSERVED IN THE NW GULF STILL UNDER THE INFLUENCE OF ELY UPPER FLOW ON THE S PERIPHERY OF A STRONG UPPER RIDGE CENTERED OVER THE TEXAS PANHANDLE. MOISTURE IS ANTICIPATED TO BE ON THE INCREASE OVER THE NEXT COUPLE OF DAYS AS THE UPPER LOW/TROPICAL WAVE TRACK NWWD DRAWING THE DEEPER MOISTURE INTO THE SRN HALF OF THE REGION. CARIBBEAN SEA... A CONSIDERABLE AMOUNT OF MOISTURE REMAINS ACROSS THE AREA W OF 75W. THE CONTRIBUTING LOW-LEVEL FEATURES CONSIST OF A PAIR OF TROPICAL WAVES. LIFT NEAR THESE BOUNDARIES ALONG WITH DIFFLUENCE ALOFT IS SUSTAINING SCATTERED SHOWERS AND TSTMS FROM 12N-22N BETWEEN 77W-90W. VISIBLE IMAGERY SHOWS SOME TURNING NEAR SW CUBA...WHICH IS COINCIDENTALLY BETWEEN THE ANALYZED WAVE PSNS. FOR MORE DETAILS REFER TO THE TROPICAL WAVES SECTION ABOVE. A LARGE UPPER LOW CENTERED OVER THE NRN LEEWARD ISLANDS IS DRAWING MUCH DRIER AIR FROM THE N AND SPREADING IT ACROSS THE E CARIB WATERS...ROUGHLY N OF 14N E OF 70W. SCATTERED SHOWERS AND TSTMS EXIST NEAR THE BASE OF THE UPPER LOW AND THE ASSOCIATED SELY JET S OF 14N E OF 67W...WHICH INCLUDES THE SRN WINDWARDS. AN 11Z QSCAT PASS SHOWS A LARGE AREA OF FRESH TO STRONG TRADES ACROSS THE E AND CENTRAL CARIB. THESE WINDS ARE EXPECTED TO INCREASE SLIGHTLY AND SPREAD W TOMORROW BEFORE DECREASING ON TUE AND WED. THE ATLANTIC OCEAN... UPPER DIFFLUENCE BETWEEN THE AFOREMENTIONED UPPER LOW LOCATED NEAR THE LOWER FLORIDA KEYS AND WEAK UPPER RIDGING NEAR 30N75W IS SUPPORTING CLOUDINESS AND SCATTERED SHOWERS AND TSTMS ACROSS THE BAHAMAS AND OFFSHORE WATERS. SLIGHTLY LIGHTER ACTIVITY IS STRUNG OUT ALONG 32N/33N ASSOCIATED WITH A STALLED FRONTAL BOUNDARY WHICH RUNS E-W FROM THE SE U.S. COAST TO BEYOND BERMUDA. ELONGATED UPPER TROUGHING LIES FURTHER E WITH TWO EMBEDDED UPPER LOWS ONE NEAR 25N50W AND THE OTHER OVER THE NRN LEEWARD ISLANDS. DEBRIS CIRRUS ARE BEING ADVECTED BY A SELY JET NEAR THE SRN UPPER LOW CONTAINED S OF 20N BETWEEN 51W-61W AND W OF THE NRN UPPER LOW FROM 25N-28N BETWEEN 56W-61W. UPPER RIDGING DOMINATES THE PATTERN E OF THE TROUGH WITH AN ANTICYCLONE PARKED NEAR 23N30W. ABUNDANT DRY AIR ALOFT COVERS MUCH OF THE ATLC...ESPECIALLY IN THE SUBTROPICS WHERE THE FLOW IS CONFLUENT BETWEEN THE RIDGE AND A TROUGH N OF THE REGION. AT THE SFC...THE MAIN WEATHER FEATURE IS A STATIONARY 1026 MB HIGH CENTERED S OF THE AZORES NEAR 34N30W. THIS MODEST HIGH PRES SYSTEM IS PRODUCING WIDESPREAD LIGHT TO MODERATE WINDS ACROSS THE BULK OF THE ATLC BASIN...EXCEPT IN THE TYPICAL STRONGER AREAS NEAR THE AFRICAN COAST AND THE CARIB ISLANDS WHERE THE GRADIENT IS SLIGHTLY TIGHTER. $$ CANGIALOSI