Forecast Thoughts on Isaac – Sunday 4 a.m.
August 26, 2012 Leave a comment
As of the 4 a.m. advisory a Hurricane Watch has been issued from the mouth of the Mississippi River eastward to Indian Pass, Florida. This includes Alabama’s gulf coast. The latest estimated track from the National Hurricane Center estimates that Isaac will make landfall in Mobile Bay. Of course there is still a day or so before we can say with any certainty where Isaac will make landfall. The most recent models are trending more toward the west, which is why the NHC moved their track. There is still a lot to be determined.
Tropical Storm Isaac continues to head northwest toward the Gulf of Mexico and as is has for the past 3 days, the forecast continues to change hour by hour. Looking at the satellite image to the left, you can see that Isaac is a very disorganized storm, but that is expected to change today. The pressure in the center continues to drop and the thunderstorm activity grows, which is an indication that the storm is strengthening. Hurricane Hunter aircraft that is flying through the storm are getting winds above hurricane strength, so Isaac will likely become a hurricane later today. There are several factors that are still influencing the strength and track of Isaac. There is dry air off to the west of Isaac that is keeping a lid on some of the development for the time being. There is also a good but of shear to the northwest of the storm. Both are expected to diminish today.
As for the track of Isaac, if you look at the image to the left you can see that the models vary greatly on where they believe the storm
will go. Since Thursday we have watched every six hours the models move from east to west. Now the models widely differ on the eventual track of Isaac. We should have a much better idea on Monday as to who will get which effects from Isaac. We will all likely see heavy rain and wind from the storm, but it is still unknown who will have get flooding and isolated tornadoes. This will also depend on how intense Isaac is when it makes landfall. The track of Isaac has a direct influence on how strong the storm becomes. If Isaac spends more time over the central Gulf of Mexico it will have more time to build strength. You can see that there is some variation in the strength predictions with one have this becoming a major hurricane in the next couple of days. The track predictions vary so widely because of the weather going on over the continental U.S. There is a trough of the jet stream that is dipping down into the southern part of the country. The exact location of this trough will determine where Isaac will head. If the trough dips far enough into the Southeast by Tuesday it will likely pull Isaac northward, if the trough lifts northward, Isaac will be able to push more to the west. Below is the 4 a.m. advisory on Tropical Storm Isaac.
TROPICAL STORM ISAAC ADVISORY NUMBER 21
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
500 AM EDT SUN AUG 26 2012
…ISAAC A LITTLE STRONGER…EXPECTED TO APPROACH THE FLORIDA KEYS LATER TODAY…HURRICANE WATCH ISSUED FOR PART OF THE NORTHERN GULF COAST…
SUMMARY OF 500 AM EDT…0900 UTC…INFORMATION
ABOUT 205 MI…330 KM ESE OF KEY WEST FLORIDA
ABOUT 215 MI…350 KM E OF HAVANA CUBA
MAXIMUM SUSTAINED WINDS…65 MPH…100 KM/H
PRESENT MOVEMENT…NW OR 305 DEGREES AT 18 MPH…30 KM/H
MINIMUM CENTRAL PRESSURE…995 MB…29.38 INCHES
WATCHES AND WARNINGS
CHANGES WITH THIS ADVISORY…
A HURRICANE WATCH HAS BEEN ISSUED FROM THE MOUTH OF THE MISSISSIPPI RIVER EASTWARD TO INDIAN PASS FLORIDA…NOT INCLUDING METROPOLITAN NEW ORLEANS.
THE TROPICAL STORM WARNING HAS BEEN EXTENDED NORTHWARD AND WESTWARD ALONG THE FLORIDA WEST COAST AND THE FLORIDA PANHANDLE TO INDIAN PASS.
THE GOVERNMENT OF THE BAHAMAS HAS DISCONTINUED THE TROPICAL STORM WARNING FOR THE TURKS AND CAICOS ISLANDS.
SUMMARY OF WATCHES AND WARNINGS IN EFFECT…
A HURRICANE WARNING IS IN EFFECT FOR…
* THE FLORIDA KEYS INCLUDING THE DRY TORTUGAS
* THE WEST COAST OF FLORIDA FROM BONITA BEACH SOUTHWARD TO OCEAN REEF
* FLORIDA BAY
* ANDROS ISLAND IN THE BAHAMAS
A HURRICANE WATCH IS IN EFFECT FOR…
* THE FLORIDA EAST COAST FROM GOLDEN BEACH SOUTHWARD TO OCEAN REEF
* THE MOUTH OF THE MISSISSIPPI RIVER TO INDIAN PASS FLORIDA…NOT INCLUDING METROPOLITAN NEW ORLEANS
A TROPICAL STORM WARNING IS IN EFFECT FOR…
* CUBAN PROVINCES OF CIEGO DE AVILA…SANCTI SPIRITUS…VILLA CLARA…CAMAGUEY…LAS TUNAS…GRANMA…HOLGUIN…SANTIAGO DE CUBA…AND GUANTANAMO
* THE BAHAMAS EXCLUDING ANDROS ISLAND
* THE FLORIDA EAST COAST FROM SEBASTIAN INLET SOUTHWARD TO OCEAN REEF
* LAKE OKEECHOBEE
* THE FLORIDA WEST COAST AND THE FLORIDA PANHANDLE FROM NORTH OF BONITA BEACH TO INDIAN PASS…INCLUDING TAMPA BAY
A TROPICAL STORM WATCH IS IN EFFECT FOR…
* CUBAN PROVINCES OF MATANZAS AND CIENFUEGOS
* THE FLORIDA EAST COAST NORTH OF SEBASTIAN INLET TO FLAGLER BEACH
A HURRICANE WARNING MEANS THAT HURRICANE CONDITIONS ARE EXPECTED SOMEWHERE WITHIN THE WARNING AREA…IN THIS CASE WITHIN THE NEXT 24 HOURS. PREPARATIONS TO PROTECT LIFE AND PROPERTY SHOULD BE RUSHED TO COMPLETION.
A HURRICANE WATCH MEANS THAT HURRICANE CONDITIONS ARE POSSIBLE WITHIN THE WATCH AREA. A WATCH IS TYPICALLY ISSUED 48 HOURS BEFORE THE ANTICIPATED FIRST OCCURRENCE OF TROPICAL-STORM-FORCE WINDS…CONDITIONS THAT MAKE OUTSIDE PREPARATIONS DIFFICULT OR DANGEROUS.
A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS.
A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE POSSIBLE WITHIN THE WATCH AREA…GENERALLY WITHIN 48 HOURS.
INTERESTS IN THE REMAINDER OF CUBA…THE REMAINDER OF FLORIDA…AND THE REMAINDER OF THE NORTHERN GULF COAST SHOULD MONITOR THE PROGRESS OF ISAAC.
FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED STATES…INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS…PLEASE MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE FORECAST OFFICE. FOR STORM INFORMATION SPECIFIC TO YOUR AREA OUTSIDE THE UNITED STATES…PLEASE MONITOR PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.
DISCUSSION AND 48-HOUR OUTLOOK
AT 500 AM EDT…0900 UTC…THE CENTER OF TROPICAL STORM ISAAC WAS LOCATED NEAR LATITUDE 23.1 NORTH…LONGITUDE 79.0 WEST. ISAAC IS MOVING TOWARD THE NORTHWEST NEAR 18 MPH…30 KM/H. A WEST- NORTHWESTWARD TO NORTHWESTWARD MOTION IS EXPECTED DURING THE NEXT 48 HOURS WITH A GRADUAL DECREASE IN FORWARD SPEED. ON THE FORECAST TRACK…THE CENTER OF ISAAC IS EXPECTED TO MOVE JUST NORTH OF THE NORTH COAST OF CUBA THIS MORNING…MOVE NEAR OR OVER THE FLORIDA KEYS LATER TODAY AND TONIGHT…AND MOVE INTO THE EASTERN GULF OF MEXICO ON MONDAY.
DATA FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INDICATE THAT MAXIMUM SUSTAINED WINDS HAVE INCREASED TO NEAR 65 MPH…100 KM/H…WITH HIGHER GUSTS. SOME ADDITIONAL STRENGTHENING IS FORECAST DURING THE NEXT 48 HOURS…AND ISAAC IS EXPECTED TO BE AT OR NEAR HURRICANE STRENGTH WHEN IT REACHES THE FLORIDA KEYS.
TROPICAL-STORM-FORCE WINDS EXTEND OUTWARD UP TO 205 MILES…335 KM FROM THE CENTER.
THE LATEST MINIMUM CENTRAL PRESSURE REPORTED BY THE AIRCRAFT WAS 995 MB…29.38 INCHES.
HAZARDS AFFECTING LAND
RAINFALL…TOTAL RAINFALL ACCUMULATIONS OF 4 TO 8 INCHES…WITH MAXIMUM AMOUNTS OF 12 INCHES…ARE POSSIBLE ACROSS THE FLORIDA KEYS…THE SOUTHERN PENINSULA OF FLORIDA AND PORTIONS OF CENTRAL AND EASTERN CUBA. TOTAL RAIN ACCUMULATIONS OF 3 TO 6 INCHES ARE POSSIBLE OVER THE CENTRAL AND SOUTHERN BAHAMAS.
WIND…TROPICAL STORM CONDITIONS ARE OCCURRING OVER PORTIONS OF EASTERN AND CENTRAL CUBA AND THE BAHAMAS AND THE TURKS AND CAICOS ISLANDS. HURRICANE CONDITIONS ARE EXPECTED ON ANDROS ISLAND ON SUNDAY. TROPICAL STORM CONDITIONS ARE POSSIBLE IN PORTIONS OF NORTHWESTERN CUBA BY LATE SUNDAY.
HURRICANE CONDITIONS ARE EXPECTED IN THE HURRICANE WARNING AREA IN SOUTHWEST FLORIDA AND THE FLORIDA KEYS TODAY…WITH TROPICAL STORM CONDITIONS EXPECTED LATER THIS MORNING. HURRICANE CONDITIONS ARE POSSIBLE IN THE HURRICANE WATCH AREA IN SOUTHEAST FLORIDA TODAY…WITH TROPICAL STORM CONDITIONS EXPECTED IN THE TROPICAL STORM WARNING AREA ALONG THE FLORIDA EAST COAST BY THIS MORNING. TROPICAL STORM CONDITIONS ARE EXPECTED TO SPREAD NORTHWARD ALONG THE WEST COAST OF FLORIDA AND INTO THE EASTERN FLORIDA PANHANDLE IN THE TROPICAL STORM WARNING AREA TONIGHT AND MONDAY.
HURRICANE CONDITIONS ARE POSSIBLE IN THE HURRICANE WATCH AREA ALONG THE NORTHERN GULF COAST ON TUESDAY…WITH TROPICAL STORM CONDITIONS POSSIBLE BY MONDAY NIGHT.
STORM SURGE…THE COMBINATION OF A STORM SURGE AND THE TIDE WILL CAUSE NORMALLY DRY AREAS NEAR THE COAST TO BE FLOODED BY RISING WATERS. THE WATER COULD REACH THE FOLLOWING DEPTHS ABOVE GROUND IF THE PEAK SURGE OCCURS AT THE TIME OF HIGH TIDE…
* CRYSTAL RIVER THROUGH THE BIG BEND OF FLORIDA…4 TO 7 FT
* SOUTHWEST FLORIDA COAST WITHIN HURRICANE WARNING AREA…4 TO 6 FT
* FLORIDA WEST COAST FROM BONITA BEACH TO SOUTH OF CRYSTAL RIVER INCLUDING TAMPA BAY…3 TO 5 FT
* SOUTHEAST FLORIDA COAST AND THE FLORIDA KEYS…1 TO 3 FT
* CENTRAL AND EASTERN CUBA…1 TO 3 FT
* THE BAHAMAS…1 TO 3 FT
THE DEEPEST WATER WILL OCCUR ALONG THE IMMEDIATE COAST IN AREAS OF ONSHORE FLOW. SURGE-RELATED FLOODING DEPENDS ON THE RELATIVE TIMING OF THE SURGE AND THE TIDAL CYCLE…AND CAN VARY GREATLY OVER SHORT DISTANCES. FOR INFORMATION SPECIFIC TO YOUR AREA…PLEASE SEE PRODUCTS ISSUED BY YOUR LOCAL WEATHER SERVICE OFFICE. NEAR THE COAST…THE SURGE WILL BE ACCOMPANIED BY DANGEROUS WAVES.
TORNADOES…ISOLATED TORNADOES ARE POSSIBLE OVER PORTIONS OF CENTRAL AND SOUTHERN FLORIDA AND THE FLORIDA KEYS ON SUNDAY.
SURF…DANGEROUS SURF AND RIP CURRENT CONDITIONS WILL CONTINUE TO AFFECT THE BAHAMAS…THE TURKS AND CAICOS…EASTERN AND CENTRAL CUBA…THE FLORIDA PENINSULA AND THE FLORIDA KEYS DURING THE NEXT COUPLE OF DAYS. PLEASE CONSULT PRODUCTS FROM YOUR LOCAL WEATHER OFFICE FOR MORE INFORMATION.
NEXT INTERMEDIATE ADVISORY…800 AM EDT.
NEXT COMPLETE ADVISORY…1100 AM EDT.