BULLETIN TROPICAL DEPRESSION THIRTEEN ADVISORY NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL AL132011 1000 AM CDT FRI SEP 02 2011 ...DEPRESSION NEARLY STATIONARY SOUTH OF THE LOUISIANA COAST... RAINBANDS MOVING ACROSS MUCH OF SOUTHEASTERN LOUISIANA... SUMMARY OF 1000 AM CDT...1500 UTC...INFORMATION ----------------------------------------------- LOCATION...27.3N 91.5W ABOUT 190 MI...310 KM SW OF THE MOUTH OF THE MISSISSIPPI RIVER ABOUT 230 MI...370 KM SE OF PORT ARTHUR TEXAS MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H PRESENT MOVEMENT...NW OR 325 DEGREES AT 2 MPH...4 KM/H MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY... NONE SUMMARY OF WATCHES AND WARNINGS IN EFFECT... A TROPICAL STORM WARNING IS IN EFFECT FOR... * PASCAGOULA MISSISSIPPI WESTWARD TO SABINE PASS TEXAS...INCLUDING THE CITY OF NEW ORLEANS...LAKE PONTCHARTRAIN...AND LAKE MAUREPAS A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE EXPECTED SOMEWHERE WITHIN THE WARNING AREA...IN THIS CASE WITHIN THE NEXT 24 HOURS. FOR STORM INFORMATION SPECIFIC TO YOUR AREA ...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE FORECAST OFFICE. DISCUSSION AND 48-HOUR OUTLOOK ------------------------------ AT 1000 AM CDT...1500 UTC...THE CENTER OF TROPICAL DEPRESSION THIRTEEN WAS LOCATED NEAR LATITUDE 27.3 NORTH...LONGITUDE 91.5 WEST. THE DEPRESSION IS DRIFTING TOWARD THE NORTHWEST NEAR 2 MPH...4 KM/H. A CONTINUED SLOW AND POSSIBLY ERRATIC MOTION TOWARD THE NORTHWEST OR NORTH IS EXPECTED TODAY AND SATURDAY. ON THE FORECAST TRACK... THE CENTER OF THE CYCLONE IS EXPECTED TO APPROACH THE COAST OF SOUTHERN LOUISIANA DURING THE WEEKEND. MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/H...WITH HIGHER GUSTS. GRADUAL STRENGTHENING IS FORECAST DURING THE NEXT 48 HOURS AND THE DEPRESSION COULD BECOME A TROPICAL STORM LATER TODAY. WINDS OF TROPICAL STORM FORCE ARE BEING REPORTED ON OIL RIGS NORTH AND EAST OF THE CENTER AT ELEVATIONS OF A FEW HUNDRED FEET. THE ESTIMATED MINIMUM CENTRAL PRESSURE BASED ON REPORTS FROM NEARBY OIL RIGS AND AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT IS 1005 MB...29.68 INCHES. HAZARDS AFFECTING LAND ---------------------- RAINFALL...THE DEPRESSION IS EXPECTED TO PRODUCE TOTAL RAIN ACCUMULATIONS OF 10 TO 15 INCHES OVER SOUTHERN LOUISIANA...SOUTHERN MISSISSIPPI...AND SOUTHERN ALABAMA THROUGH SUNDAY...WITH POSSIBLE ISOLATED MAXIMUM AMOUNTS OF 20 INCHES. THESE RAINS ARE EXPECTED TO CAUSE EXTENSIVE FLOODING. STORM SURGE...A STORM SURGE WILL RAISE WATER LEVELS BY AS MUCH AS 2 TO 4 FEET ABOVE GROUND LEVEL ALONG THE NORTHERN GULF COAST IN AREAS OF ONSHORE FLOW. WIND...TROPICAL STORM CONDITIONS ARE EXPECTED TO FIRST REACH THE COAST WITHIN THE WARNING AREA THIS EVENING...MAKING OUTSIDE PREPARATIONS DIFFICULT OR DANGEROUS. TORNADOES...ISOLATED TORNADOES ARE POSSIBLE OVER PORTIONS OF SOUTHERN LOUISIANA TONIGHT. NEXT ADVISORY ------------- NEXT INTERMEDIATE ADVISORY...100 PM CDT. NEXT COMPLETE ADVISORY...400 PM CDT. $$ FORECASTER STEWART
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TROPICAL DEPRESSION THIRTEEN DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL132011 400 AM CDT FRI SEP 02 2011 SATELLITE IMAGERY...SURFACE OBSERVATIONS...AND AN EARLIER ASCAT OVERPASS INDICATE THAT TROPICAL DEPRESSION THIRTEEN HAS A ELONGATED CENTER OF CIRCULATION...WITH THE ELONGATION CURRENTLY FROM EAST-NORTHEAST TO WEST-SOUTHWEST. THE ASSOCIATED CONVECTION IS CURRENTLY POORLY ORGANIZED...ALTHOUGH A STRONG BURST HAS RECENTLY FORMED NEAR THE EAST-NORTHEASTERN END OF THE CENTER. THE INITIAL INTENSITY REMAINS 30 KT BASED ON THE ASCAT OVERPASS AND REPORTS FROM OIL RIGS IN THE NORTHERN GULF. WHILE THERE IS GOOD OUTFLOW OVER THE EASTERN SEMICIRCLE...AN UPPER-LEVEL TROUGH IS PRESENT OVER THE WESTERN SIDE OF THE CIRCULATION. THE DEPRESSION HAS NOT MOVED MUCH DURING THE PAST SEVERAL HOURS... WITH THE INITIAL MOTION A HIGHLY UNCERTAIN 315/2. THE CYCLONE IS CURRENTLY IN AN AREA OF LIGHT STEERING CURRENTS SOUTH OF A MID-LEVEL RIDGE OVER THE MISSISSIPPI VALLEY. THE DYNAMICAL MODELS FORECAST THIS RIDGE TO MOVE EASTWARD AND WEAKEN AS A DEEP-LAYER TROUGH MOVES SOUTHEASTWARD INTO THE OHIO VALLEY. THIS EVOLUTION SHOULD ALLOW THE DEPRESSION TO MOVE SLOWLY NORTHWESTWARD TO NORTHWARD FOR THE NEXT 24-36 HR...FOLLOWED BY A GRADUAL TURN TOWARD THE NORTHEAST. MOST OF THE DYNAMICAL MODELS NOW SHOW THIS SCENARIO...ALTHOUGH THERE REMAINS ENOUGH DISAGREEMENT BETWEEN THEM TO KEEP THIS A LOW CONFIDENCE FORECAST. THE NEW FORECAST TRACK IS ADJUSTED SOUTH AND EAST OF THE PREVIOUS FORECAST BASED MAINLY ON THE INITIAL POSITION...AND LIES CLOSE TO THE VARIOUS CONSENSUS MODELS FOR THE FIRST THREE DAYS OF THE FORECAST. IT SHOULD BE NOTED THAT REFORMATIONS OF THE CENTER COULD CAUSE ERRATIC MOTION AND ADJUSTMENTS TO THE FORECAST TRACK DURING THE NEXT COUPLE OF DAYS. THE CURRENT INTERACTION WITH THE UPPER-LEVEL TROUGH IS FORECAST BY THE DYNAMICAL MODELS TO CONTINUE FOR AT LEAST THE NEXT COUPLE OF DAYS...RESULTING IN VERTICAL WIND SHEAR CONDITIONS THAT...AT BEST...WILL BE MARGINALLY FAVORABLE FOR INTENSIFICATION. THIS INTERACTION...COMBINED WITH THE CURRENT ORGANIZATION OF THE SYSTEM...SUGGESTS THAT STRENGTHENING SHOULD BE SLOW. THE NEW INTENSITY FORECAST IS UNCHANGED FROM THE PREVIOUS ADVISORY AND LIES BETWEEN THE STRONGER SHIPS AND WEAKER LGEM MODELS. THE LARGE SIZE AND SLOW MOTION OF THE CYCLONE DURING THE NEXT 5 DAYS IS LIKELY TO PRODUCE A PROLONGED PERIOD OF TROPICAL STORM CONDITIONS AND HEAVY RAINFALL OVER PORTIONS OF THE NORTHERN GULF COAST.
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