Hurricane Gustav Advisory 28 Plus Forecast Discussion

BULLETIN
HURRICANE GUSTAV ADVISORY NUMBER 28
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072008
10:00 AM CDT SUN AUG 31 2008
GUSTAV CONTINUES NORTHWESTWARD OVER THE CENTRAL GULF OF MEXICO WITH LITTLE
CHANGE IN STRENGTH.
A HURRICANE WARNING REMAINS IN EFFECT FOR THE NORTHERN GULF COAST FROM
CAMERON LOUISIANA EASTWARD TO THE ALABAMA-FLORIDA BORDER, INCLUDING THE CITY
OF NEW ORLEANS AND LAKE PONTCHARTRAIN. A HURRICANE WARNING MEANS THAT
HURRICANE CONDITIONS ARE EXPECTED WITHIN THE WARNING AREA WITHIN THE NEXT 24
HOURS. PREPARATIONS TO PROTECT LIFE AND PROPERTY SHOULD BE RUSHED TO
COMPLETION.
A TROPICAL STORM WARNING REMAINS IN EFFECT FROM EAST OF THE ALABAMA-FLORIDA
BORDER TO THE OCHLOCKONEE RIVER., AND FROM WEST OF CAMERON LOUISIANA TO JUST
EAST OF HIGH ISLAND TEXAS. A TROPICAL STORM WARNING MEANS THAT TROPICAL
STORM CONDITIONS ARE EXPECTED WITHIN THE WARNING AREA WITHIN THE NEXT 24
HOURS.
A HURRICANE WATCH REMAINS IN EFFECT FROM WEST OF CAMERON LOUISIANA TO JUST
EAST OF HIGH ISLAND TEXAS. A HURRICANE WATCH MEANS THAT HURRICANE
CONDITIONS ARE POSSIBLE WITHIN THE WATCH AREA, GENERALLY WITHIN 36 HOURS.
A TROPICAL STORM WARNING REMAINS IN EFFECT FOR THE LOWER FLORIDA KEYS WEST
OF THE SEVEN MILE BRIDGE TO THE DRY TORTUGAS. FOR STORM INFORMATION SPECIFIC
TO YOUR AREA, INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS, PLEASE MONITOR
PRODUCTS ISSUED BY YOUR LOCAL WEATHER OFFICE.
AT 10:00 AM CDT, 15:00Z, THE CENTER OF HURRICANE GUSTAV WAS LOCATED NEAR
LATITUDE 25.3 NORTH, LONGITUDE 86.0 WEST, OR ABOUT 325 MILES, 520 KM
SOUTHEAST OF THE MOUTH OF THE MISSISSIPPI RIVER. GUSTAV IS MOVING TOWARD THE
NORTHWEST NEAR 17 MPH. THIS GENERAL MOTION IS EXPECTED TO CONTINUE WITH A
DECREASE IN FORWARD SPEED DURING THE NEXT COUPLE OF DAYS. ON THIS FORECAST
TRACK, GUSTAV SHOULD MAKE LANDFALL ON THE NORTHERN GULF COAST ON MONDAY.
MAXIMUM SUSTAINED WINDS ARE NEAR 120 MPH, WITH HIGHER GUSTS. GUSTAV IS A
CATEGORY THREE HURRICANE ON THE SAFFIR-SIMPSON SCALE. SOME
RE-INTENSIFICATION IS FORECAST DURING THE NEXT 12 TO 24 HOURS, AND GUSTAV
COULD REGAIN CATEGORY FOUR STRENGTH LATER TODAY OR TONIGHT. FLUCTUATIONS IN
STRENGTH ARE LIKELY THEREAFTER, BUT GUSTAV IS FORECAST TO REMAIN A MAJOR
HURRICANE UNTIL LANDFALL.
GUSTAV IS A LARGE TROPICAL CYCLONE. HURRICANE FORCE WINDS EXTEND OUTWARD UP
TO 50 MILES FROM THE CENTER, AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD
UP TO 200 MILES. NOAA BUOY 42003 RECENTLY REPORTED 8-MINUTE AVERAGE WINDS
OF 54 MPH, WITH A GUST TO 67 MPH. THE MINIMUM CENTRAL PRESSURE JUST REPORTED
BY A NOAA HURRICANE HUNTER AIRCRAFT IS 962 MB, 28.41 INCHES.
AN EXTREMELY DANGEROUS STORM SURGE OF 12 TO 16 FEET ABOVE NORMAL TIDAL
LEVELS IS EXPECTED NEAR AND TO THE EAST OF WHERE THE CENTER OF GUSTAV
CROSSES THE NORTHERN GULF COAST. A STORM SURGE OF 1 TO 3 FEET ABOVE NORMAL
TIDE LEVELS IS POSSIBLE IN THE DRY TORTUGAS AS GUSTAV PASSES TO ITS WEST.
GUSTAV IS EXPECTED TO PRODUCE TOTAL RAINFALL ACCUMULATIONS OF 6 TO 12 INCHES
OVER PORTIONS OF LOUISIANA, SOUTHERN MISSISSIPPI AND
SOUTHERN ARKANSAS, WITH ISOLATED MAXIMUM AMOUNTS OF UP TO 20 INCHES POSSIBLE
THROUGH WEDNESDAY MORNING. ADDITIONAL RAINFALL AMOUNTS OF ABOUT AN INCH
ARE POSSIBLE OVER THE FLORIDA KEYS AND SOUTH FLORIDA. ISOLATED TORNADOES ARE
POSSIBLE OVER THE CENTRAL GULF COAST LATER TODAY AND TONIGHT.
REPEATING THE 10 AM CDT POSITION, 25.3 N, 86.0 W. MOVEMENT TOWARD,
NORTHWEST NEAR 17 MPH. MAXIMUM SUSTAINED WINDS, 120 MPH. MINIMUM CENTRAL
PRESSURE, 960 MB. AN INTERMEDIATE ADVISORY WILL BE ISSUED BY THE NATIONAL
HURRICANE CENTER AT 1 PM CDT, FOLLOWED BY THE NEXT COMPLETE ADVISORY AT 4 PM
CDT.
HURRICANE GUSTAV DISCUSSION NUMBER 28
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072008
11 AM EDT SUN AUG 31 2008
GUSTAV CONTINUES TO LOOK SOMEWHAT RAGGED IN SATELLITE APPEARANCE
THIS MORNING. THE DEEP CONVECTION IS VERY ASYMMETRIC, WITH THE
COLD TOPS DUE MAINLY TO ONE HOT TOWER IN THE WESTERN EYE WALL.
WHILE AN EYE-LIKE FEATURE IS APPARENT, IT IS DISPLACED TO THE
NORTHEAST OF THE AIRCRAFT-REPORTED CENTER. THE LATEST REPORT FROM
A NOAA HURRICANE HUNTER INDICATES THE CENTRAL PRESSURE HAS RISEN TO
962 MB, ALONG WITH AN ELLIPTICAL 30 BY 20 N MI WIDE EYE OPEN TO THE
SOUTHEAST. THE INITIAL INTENSITY IS REDUCED TO 105 KT...AND THIS
MIGHT BE A LITTLE GENEROUS BASED ON THE AIRCRAFT WINDS.
THE INITIAL MOTION IS 320/15. THERE IS NO CHANGE IN THE FORECAST
PHILOSOPHY FOR THE EARLY PORTION OF THE FORECAST TRACK, WITH A
MID-LEVEL RIDGE OVER THE EASTERN UNITED STATES EXPECTED TO STEER
GUSTAV NORTHWESTWARD INTO THE NORTHERN GULF COAST. THE NEW
GUIDANCE RUNS SHOW A SLIGHT LEFT TURN AFTER 12 HR WITH A LEFTWARD
SHIFT IN THE LANDFALL POINT ON THE LOUISIANA COAST. THE NEW
FORECAST TRACK WILL NOT FOLLOW THIS SHIFT YET, AND THUS LIES NEAR
THE EASTERN EDGE OF THE GUIDANCE ENVELOPE AND THE PREVIOUS FORECAST
TRACK THROUGH 48 HR. AFTER 48-72 HR, THERE IS MAJOR DISAGREEMENT
BETWEEN THE DYNAMICAL MODELS ON WHETHER GUSTAV WILL RECURVE INTO
THE WESTERLIES, STALL OVER LOUISIANA OR TEXAS, OR TURN
SOUTHWESTWARD. SINCE THIS KIND OF SPREAD FREQUENTLY PRECEDES SLOW
MOTION, THE FORECAST TRACK WILL CALL FOR A SLOW WESTWARD MOTION
AFTER 72 HR.
AT THE RISK OF SOUNDING LIKE A BROKEN RECORD, THE INTENSITY
FORECAST REMAINS PROBLEMATIC. ANALYSES FROM CIMSS AT THE
UNIVERSITY OF WISCONSIN SHOWS THAT GUSTAV REMAINS IN 15 TO 20 KT OF
SOUTHERLY VERTICAL SHEAR, AND THE LARGE-SCALE MODELS FORECAST AT
LEAST SOME SOUTHERLY TO SOUTHWESTERLY SHEAR TO PERSIST UNTIL
LANDFALL. THAT...COMBINED WITH THE CURRENT RAGGED STORM STRUCTURE
AND THE MID-LEVEL DRY AIR TRYING TO WRAP AROUND THE STORM IN WATER
VAPOR IMAGERY, SUGGESTS ANY INTENSIFICATION SHOULD BE SLOW.
ADDITIONALLY, GUSTAV IS OVER A WARM EDDY IN THE LOOP CURRENT
NOW, AND SHOULD PASS OVER WATERS WITH LOWER OCEANIC HEAT CONTENT
BETWEEN NOW AND LANDFALL. THE GUIDANCE RESPONDS TO THESE FACTORS
BY FORECASTING MODEST STRENGTHENING DURING THE NEXT 12 TO 24
HR, WITH THE GFDL FORECASTING A PEAK INTENSITY OF 120 KT AND THE
OTHER MODELS ABOUT 110 KT. BASED ON THIS, THE INTENSITY FORECAST
WILL CALL FOR GUSTAV TO RE-INTENSIFY TO 115 KT IN 12 TO 24 HR, AND
MAKE LANDFALL ON THE NORTHERN GULF COAST AS A MAJOR HURRICANE.
GUSTAV SHOULD STEADILY WEAKEN AFTER LANDFALL.