Isaac Moves Into Southeastern Gulf

Storm Could Get As Strong As Category Two At Landfall Along Northern Gulf Coast

On Sunday, Tropical Storm Isaac spent the entire day lashing South Florida and the Keys with its 60 to 65 mile per hour winds. Fortunately, forecasts that called for the storm to become a hurricane prior to moving through the Florida Keys didn’t come to pass. Now, Isaac is moving into the Gulf of Mexico with no land masses to interact with prior to making a landfall along the Northern Gulf coast by the middle of the week.

Since it has been in the Eastern Caribbean, Isaac has struggled to get its act together. Battling dry air, an upper level low in the Western Caribbean and Yucatan Peninsula, and the rugged terrain of Hispaniola and Cuba, the vast storm system has not been able to get strong enough to become the season’s fourth hurricane. Much of the precipitation has been staying to the north of the center of circulation as the upper low is pushing dry air into the southern side of the storm. As a result, the storm is asymmetric in shape.

With Isaac moving into the Southeastern Gulf, shower and thunderstorm activity has increased on the northern side. If the upper level low over the Yucatan can move away from the storm, there will be plenty of warm water and optimal upper level conditions for intensification. The National Hurricane Center has been indicating in their forecast discussions that Isaac could strengthen to a Category Two Hurricane on the Saffir-Simpson Scale with 100 mile per hour winds by the time it makes landfall.

Another trend that has been developing is a more westward forecast track with the storm. Late last week and into this weekend, the models had been indicating an impact further to the east along the Northeastern Gulf from the Florida Panhandle southward to places such as Tampa along the West Coast of Florida. Little by little though the track has been shifting to the left. Now, the storm could make landfall anywhere along the Northern Gulf coast from Louisiana to the Florida Panhandle. The timing of the landfall appears to be some time mid-week, which would be ironic for New Orleans, which was impacted by Hurricane Katrina seven years to the day on Wednesday.

Currently, Isaac is located about 60 miles Southwest of Key West, Florida, or about 530 miles to the Southeast of the Mouth of the Mississippi River. The storm is moving to the West-Northwest at 15 miles per hour, and has maximum sustained winds of 65 miles per hour. Winds are gusting to near hurricane force. Barometric pressure has fallen some 9 millibars in the past 20 hours to 991 millibars or 29.26 inches of Hg, and the winds have increased five miles per hour from earlier in the day. Isaac is a large storm with tropical storm force winds extending some 200 miles from the center of circulation. The size of the storm is a big concern for forecasters since Isaac’s vast circulation will likely create high seas, storm surge, and waves along the coast prior to coming ashore.

Taking a look at the watches and warnings, a Hurricane Warning is out for the North Central Gulf coast from Morgan City, Louisiana eastward to Destin, Florida including New Orleans, Lake Pontchartrain, and Lake Murepas. A Hurricane Watch is in effect from east of Destin, Florida to Indian Pass, Florida. Tropical Storm Warnings are in effect along the Florida Peninsula from Sebastian Inlet southward on the East Coast and from Tarpon Springs southward on the West Coast, the Florida Keys including the Dry Tortugas and Florida Bay, Lake Okeechobee, and from east of Destin, Florida to the Suwanee River.

Isaac does show some signs of strengthening. However, previous attempts have ended up just being a tease. Thunderstorms would flare up for a few hours near the center of circulation, but then level off. This latest flare up has lasted some four to five hours now, and it could persist, which would be an indication of strengthening. Again, the storm’s core is lopsided due to the dry air entrainment into the system from the upper level low over the Yucatan. If the low could move further away from Isaac, less dry air would get in on the south side, and the air would moisten from the water vapor generated by the very warm waters of the Gulf (running 85 to 87 degrees).

While the forecast track is showing a more westward track to landfall along the Northern Gulf coast, there is some discrepancy between the models as to where exactly Isaac will make an impact. The European (ECMWF), UKMET, and GFS models are about 300 miles apart with the GFS taking the most western route by having the storm move over the Southwestern part of Louisiana, which is a worst case scenario for New Orleans since the city will be on the eastern side of the storm. The ECMWF is showing a landfall in Alabama, which would mean that the Big Easy would be on the western or more weaker side of the storm.

Already, the storm has left behind a toll. On the island of Hispanola, which includes Haiti and the Dominican Republic, at least 10 people are dead according to the Huffington Post. Hundreds of homes were damaged by the storm in the Dominican Republic, and many people had to brave the elements in Haiti, where most are living in tents outside Port Au-Prince following an earthquake there several years ago. The Haitian government reported a dozen homes were destroyed by the storm and some 270 were damaged.