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National Weather Service Weather Forecast Office Mobile - Pensacola Special Update Tropical Storm Isaac Special Update Tropical Storm Isaac Jeff Garmon Warning Coordination Meteorologist 4 PM CDT Monday 27 August 2012

This outlook is intended for interests across interior southeast Mississippi, south Alabama, the western Florida Panhandle, and the adjacent Gulf coastal waters of Alabama and northwest Florida

Satellite Image TS Isaac

Latest Observations… Isaac is now strengthening quickly and is near hurricane strength. Winds are at 70 mph at the core of Isaac and a clearly defined circulation center is becoming evident in the satellite imagery…and Air Force reconnaissance data indicates the eye is forming. Pressure inside the storm is dropping more rapidly as well. This all means Isaac will likely be a hurricane soon. Isaac is moving northwest at 12 mph. Isaac’s motion has turned more to the northwest and is starting to slow down a bit. Further slowing of the forward motion is expected through tomorrow…and this means that a little more error in the forecast track could be introduced. There is still a fair amount of uncertainty in the forecast as to exactly where Isaac will make landfall…but areas from southeast Louisiana to the Alabama coastline are still in the area of most concern. Isaac is now strengthening quickly and is near hurricane strength. Winds are at 70 mph at the core of Isaac and a clearly defined circulation center is becoming evident in the satellite imagery…and Air Force reconnaissance data indicates the eye is forming. Pressure inside the storm is dropping more rapidly as well. This all means Isaac will likely be a hurricane soon. Isaac is moving northwest at 12 mph. Isaac’s motion has turned more to the northwest and is starting to slow down a bit. Further slowing of the forward motion is expected through tomorrow…and this means that a little more error in the forecast track could be introduced. There is still a fair amount of uncertainty in the forecast as to exactly where Isaac will make landfall…but areas from southeast Louisiana to the Alabama coastline are still in the area of most concern.

Tropical Storm Force Winds Extend Eastward for 200 Miles

Forecast Track Impacts extend well outside the cone. The cone represents (based on average track error, where the CENTER of the hurricane will be 2/3rds of the time. Tropical storm force winds extend eastward for 200 miles.

Warning and Watches in Effect Onset of tropical storm winds ( mph) would be late tonight and Tuesday morning along the coast…with hurricane force winds possible along the Alabama coast by early Wednesday (if we see a significant track change). The Tropical Storm/Hurricane Watches may have to be extended farther inland later tonight based on trends.

Hurricane Watch and Warning (What do they mean?) Hurricane Watch - An announcement that hurricane conditions (sustained winds of 74 mph or higher) are possible within the specified area. –Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane watch is issued 48 hours in advance of the anticipated onset of tropical-storm-force winds. Hurricane Warning – An announcement that hurricane conditions (sustained winds of 74 mph or higher) are expected somewhere within the specified area. –Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane warning is issued 36 hours in advance of the anticipated onset of tropical-storm-force winds. Hurricane Watch - An announcement that hurricane conditions (sustained winds of 74 mph or higher) are possible within the specified area. –Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane watch is issued 48 hours in advance of the anticipated onset of tropical-storm-force winds. Hurricane Warning – An announcement that hurricane conditions (sustained winds of 74 mph or higher) are expected somewhere within the specified area. –Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane warning is issued 36 hours in advance of the anticipated onset of tropical-storm-force winds.

Coastal Flood Considerations

Wind Impact Considerations

Heavy Rain Threat Overall, 6-12” of rainfall is expected from Isaac over SE Mississippi and SW Alabama. Slightly lower amounts around 6 inches are expected over south central AL and the western Florida panhandle. –This could cause flooding issues…how extensive remains to be seen at this time. With the rain that we have received over the past several months, the soils are already moist. Additional rainfall, coupled with winds, could take many trees down. Overall, 6-12” of rainfall is expected from Isaac over SE Mississippi and SW Alabama. Slightly lower amounts around 6 inches are expected over south central AL and the western Florida panhandle. –This could cause flooding issues…how extensive remains to be seen at this time. With the rain that we have received over the past several months, the soils are already moist. Additional rainfall, coupled with winds, could take many trees down.

Tornado Risk We are looking at a potential isolated tornado risk beginning late tonight with the onset of the precipitation bands associated with Isaac. This will increase into Tuesday and Tuesday night as the system makes landfall. We are looking at a potential isolated tornado risk beginning late tonight with the onset of the precipitation bands associated with Isaac. This will increase into Tuesday and Tuesday night as the system makes landfall.

Main Points to Consider… Current projections indicate a strong category 2 hurricane at landfall (exactly where that happens remains in question). –Remember, in the longer ranges beyond 24 hours our forecast can be off by one category (meaning this could be a category 3 hurricane at landfall.) Conditions on Tuesday will continue to deteriorate across the area…especially along the coast. –By Tuesday AM there is a possibility the winds along the coast could be gusting 40 to 50 mph at times in passing rain squalls. Hurricane force winds projected to arrive on the coast Wednesday morning (exactly where that happens is still in question). Rough surf and dangerous rip currents will continue as swells off of Isaac move up to the coast. There is a chance that 6 to 12 inches of rain could fall over portions of our area Tuesday into Wednesday. This would result in an increased risk of freshwater flooding by Wednesday. A flash flood watch has been issued for part of the area. Tornado risks will be increasing as the hurricane approaches the coast Tuesday. Current projections indicate a strong category 2 hurricane at landfall (exactly where that happens remains in question). –Remember, in the longer ranges beyond 24 hours our forecast can be off by one category (meaning this could be a category 3 hurricane at landfall.) Conditions on Tuesday will continue to deteriorate across the area…especially along the coast. –By Tuesday AM there is a possibility the winds along the coast could be gusting 40 to 50 mph at times in passing rain squalls. Hurricane force winds projected to arrive on the coast Wednesday morning (exactly where that happens is still in question). Rough surf and dangerous rip currents will continue as swells off of Isaac move up to the coast. There is a chance that 6 to 12 inches of rain could fall over portions of our area Tuesday into Wednesday. This would result in an increased risk of freshwater flooding by Wednesday. A flash flood watch has been issued for part of the area. Tornado risks will be increasing as the hurricane approaches the coast Tuesday.

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