While still relatively weak, it has potential to become quite a big hurricane as it heads further northwest in the Gulf of Mexico where SSTs are in excess of 31C. The last couple of runs of NCEP's HWRF model suggests explosive cyclonegenesis with a track into the US Gulf Coast where it could be avoided the most. We'll see.
TROPICAL STORM ISAAC DISCUSSION NUMBER 22
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
1100 AM EDT SUN AUG 26 2012
VISIBLE SATELLITE AND IMAGERY SUGGEST THAT THE TROPICAL CYCLONE IS
GRADUALLY BECOMING BETTER ORGANIZED. THERE ARE INDICATIONS OF
INNER CORE DEVELOPMENT WITH INCREASED CONVECTION NEAR AND OVER THE
CENTER...AND A PARTIAL EYEWALL IS IN EVIDENCE ON RADAR IMAGERY. THE
BANDING FEATURES HAVE BECOME MORE DISTINCT OVER THE NORTHERN AND
EASTERN SEMICIRCLES OF THE CIRCULATION. THE CURRENT INTENSITY
ESTIMATE IS HELD AT 55 KT PENDING OBSERVATIONS FROM AN AIR FORCE
HURRICANE HUNTER AIRCRAFT THAT SHOULD BE IN THE CENTER SHORTLY.
ISAAC CONTINUES TO EXHIBIT A WELL-DEFINED UPPER-LEVEL OUTFLOW
PATTERN...AND GRADUAL STRENGTHENING IS LIKELY AS THE CYCLONE
TRAVERSES THE EASTERN GULF OF MEXICO OVER THE NEXT COUPLE OF DAYS.
THE OFFICIAL WIND SPEED FORECAST IS SIMILAR TO THE PREVIOUS NHC
FORECAST AND IS ALSO CLOSE TO THE LATEST STATISTICAL-DYNAMICAL
GUIDANCE.
THE TRACK FORECAST BEYOND DAY 2 HAS BECOME PROBLEMATIC. DYNAMICAL
MODELS DEPICT THE CYCLONE MOVING INTO A BREAK IN THE SUBTROPICAL
RIDGE NORTH OF THE GULF COAST IN ABOUT 72 HOURS. HOWEVER THERE IS
A LARGE SPREAD AMONG THE MORE RELIABLE TRACK MODELS. FOR EXAMPLE...
THE ECMWF FORECAST IS ABOUT 300 N MI EAST OF THE GFS SOLUTION AT DAY
3. SINCE THE DYNAMICAL MODEL CONSENSUS HAS SHIFTED WESTWARD...THE
OFFICIAL TRACK FORECAST IS MOVED A BIT TO THE WEST OF THE PREVIOUS
ONE. THIS REQUIRES AN EXTENSION OF THE HURRICANE WATCH WESTWARD
ALONG THE LOUISIANA COAST. IT SHOULD BE NOTED THAT THERE IS
GREATER THAN USUAL UNCERTAINTY IN THE TRACK FORECAST.
THROUGHOUT THE PERIOD...IT IS IMPORTANT NOT TO FOCUS ON THE EXACT
FORECAST TRACK SINCE SIGNIFICANT HAZARDS EXTEND WELL AWAY FROM THE
CENTER.
Yes, will be interesting to watch Isaac. The latest drop sounding has the central pressure falling so this storm looks to be ramping up. The potential tornado scenario with such tropical storms is interesting as well.
Now looking like a cat 1 or 2 hurricane making landfall around New Orleans. 18inches of rain will be the main problem. Wind damage not expected to be significant apart from a risk of small tornadoes.
Issac has become much better organised over the last 6 hours or so.
Maximum sustained (1 minute) winds of 110 km/h
Minimum Central Pressure of 981 hPa
If the peak storm surge coincides with high-tides in SE Louisiana, Mississippi and Alabama, water could reach depths above ground of 6 to 12 feet...
000
WTNT44 KNHC 272058
TCDAT4
TROPICAL STORM ISAAC DISCUSSION NUMBER 27
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
400 PM CDT MON AUG 27 2012
THE MUCH ANTICIPATED INTENSIFICATION PROCESS APPEARS TO HAVE FINALLY
STARTED BASED ON REPORTS FROM AN AIR FORCE RESERVE RECONNAISSANCE
AIRCRAFT AND FROM NEARBY NOAA BUOY 42003. THE CENTRAL PRESSURE HAS
DECREASED BY AT LEAST 7 MB SINCE THE PREVIOUS ADVISORY. THE HIGHEST
FLIGHT-LEVEL WINDS OBSERVED HAVE BEEN 74 KT IN THE SOUTHWEST
QUADRANT AND THE HIGHEST BIAS-ADJUSTED SFMR WINDS ARE NEAR 58 KT.
THESE DATA SUPPORT AN INTENSITY OF 60 KT.
ISAAC WOBBLED WESTWARD THIS AFTERNOON...BUT A REPRESENTATIVE INITIAL
MOTION ESTIMATE IS 305/10. THE LATEST 12Z NHC MODEL GUIDANCE IS IN
BETTER AGREEMENT ON A WEST-NORTHWEST TO NORTHWEST MOTION TOWARD THE
SOUTHEAST LOUISIANA AND MISSISSIPPI COASTAL AREAS OVER THE NEXT
36-48 HOURS. AFTER 48 HOURS...HOWEVER...THE MODEL GUIDANCE REMAINS
DIVERGENT ON THE HANDLING OF A SHORTWAVE TROUGH FORECAST TO DIG
SOUTHEASTWARD FROM THE UPPER MIDWEST AND INTO THE MID-ATLANTIC
REGION...FOLLOWED BY A RIDGE BUILDING IN BEHIND THE TROUGH. THE GFS
AND ECMWF...OUR MOST RELIABLE MODELS... NOW HAVE VERY SIMILAR
SOLUTIONS THROUGH DAY 5...AND THE OFFICIAL FORECAST TRACK IS
BETWEEN THOSE TWO MODELS.
SATELLITE DATA INDICATE ISAAC HAS BECOME BETTER ORGANIZED OVER THE
PAST 6 HOURS WITH THE DEVELOPMENT OF A CENTRAL DENSE OVERCAST CLOUD
PATTERN OVER THE CENTER ALONG WITH A DEVELOPING EYE IN RECON DATA.
SATELLITE DATA T-NUMBERS HAVE INCREASED TO T4.5/77 KT FROM TAFB AND
SAB. RECON WIND DATA INDICATE THE RADIUS OF MAXIMUM WINDS HAS ALSO
PULLED INWARD TO ABOUT 30 N MI. ALTHOUGH ADDITIONAL CONVECTION HAS
BEEN DEVELOPING IN THE NORTHEASTERN QUADRANT...DRY MID-LEVEL AIR
STILL LURKS JUST TO THE EAST AND SOUTHEAST OF THE CDO FEATURE...
WHICH COULD BE ENTRAINED INTO THE INNER CORE AT ANY TIME AND
DISRUPT THE DEVELOPMENT PROCESS. DUE TO THE PROXIMITY OF DRY
AIR...THE INTENSITY FORECAST INDICATES ONLY MODEST DEVELOPMENT FOR
THE NEXT 24 HOURS. HOWEVER...STRENGTHENING IS EXPECTED TO CONTINUE
RIGHT UP UNTIL LANDFALL OCCURS DUE TO THE VERY WARM WATERS THE
CYCLONE WILL BE PASSING OVER AND THE VERY FAVORABLE UPPER-LEVEL
OUTFLOW REGIME THAT ISAAC IS FORECAST TO DEVELOP BY 24 HOURS. THE
INTENSITY FORECAST IS JUST SLIGHTLY HIGHER THAN THE MODEL GUIDANCE.
BECAUSE SIGNIFICANT HAZARDS EXTEND WELL AWAY FROM THE CENTER...IT IS
IMPORTANT NOT TO FOCUS ON THE EXACT FORECAST TRACK. THE SLOW FORWARD
SPED OF AROUND 5 KT AFTER LANDFALL WILL RESULT IN A HEAVY RAIN AND
FLOOD SITUATION FOR PORTIONS OF THE CENTRAL GULF COAST AND LOWER
MISSISSIPPI VALLEY REGIONS.
Reconnaissance data from an Air Force Reserve Hurricane Hunter aircraft a couple of hours ago indicate that Isaac has finally achieved hurricane status...
Maximum sustained winds of 120 km/h
Minimum Central Pressure of 975 hPa
.
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NOAA DOPPLER RADAR INDICATES THAT HURRICANE ISAAC MADE LANDFALL
ALONG THE COAST OF SOUTHEAST LOUISIANA IN PLAQUEMINES PARISH JUST
SOUTHWEST OF THE MOUTH OF THE MISSISSIPPI RIVER AT 2345 UTC
WITH MAXIMUM SUSTAINED WINDS OF 80 MPH…130 KM/H.
