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Hurricane Isaac to have big impacts in Mississippi, Alabama and Louisiana

28 Aug 2012, 1:49 pm

Isaac was upgraded to Hurricane status early this afternoon as the storm continues to head toward the Gulf coast. The storm is expected to have some big impacts on the Gulf coast.

Isaac as of 1220 PM ET

A special update at 1220 PM ET update from the National Hurricane Center in Miami, FL upgraded Isaac to hurricane status, with winds of 75 mph. Isaac was moving to the NW at 10 mph. If you’ve been paying attention the past few days, this is weaker than expected at this time from those forecasts. There is still some mid-level dry air in the system, preventing storms to consistently be around the eye. While an eye feature may pop up on satellite or radar, it’s that dry air that is preventing it from sticking around. Isaac only has 12-18 hours or so to strengthen, so we are only going to expect a weak hurricane at landfall, despite other favorable conditions like warm water temperatures.

You can see some of the winds starting to affect the coastal areas of Mississippi, Alabama, and Louisiana on the wind map this morning.

Forecast Track

 

A weakness in the subtropical ridge is what is driving Isaac right now to the northwest, and that is expected to continue over the next couple days. After that, the ridge will build back in, eventually sending the system northeastward and into the Ohio Valley. As the system is only possibly 12 hours away from landfall, we do not expect much strengthening. We still think it will become a hurricane before landfall, with winds possibly around 80 mph. While the current forecast path of the system would have it coming ashore between Houma and New Orleans, that doesn’t mean other areas will not be greatly impacted by the storm, especially those to the west of that landfall.

This graphic from the National Hurricane Center shows where hurricane force winds are possible over the next couple days. Again, though, wind is possibly not the main concern right now.

Storm surge will be one of the main concerns from Isaac along the coastlines. Above is a graphic that shows the probability that storm surge will be over 4 feet from NOAA. There is a 50% chance or greater all the way from Biloxi to New Orleans that we could see this type of storm surge, which with the low-lying areas could be devastating, especially in Mississippi. Some of the areas worse hit in Katrina with coastal flooding from higher seas were in Mississippi, and it looks as though we could see the same situation with this storm. Depending on how low the area is, you could see water rushing inland a few miles or so. Plus, some of the storm surge will coordinate with high tide tomorrow morning, making the situation even worse. For a good explanation on what storm surge is, click here (takes you to the National Hurricane Center).

In fact, you can already see that the water is high this morning in the Mobile Bay area of Alabama. We expect to see these type of conditions over the next day or so throughout the Gulf coast region. Photo courtesy of @Courtneyb333 (Courtney Wilkerson of CMT’s Southern Nights).

We are expecting heavy rains along the path of Isaac. Some of the heaviest rains should occur in the Biloxi-Gulfport areas, but anywhere near landfall could see 12″+  of rainfall. You will notice this map of expected TS Isaac rainfall has expanded since yesterday northward to encompass the whole path of the system over the next 5 days. Even after the system moves onshore and is downgraded, we still expect a heavy rain threat from Arkansas through the Ohio Valley, where 3-6″ of rain is possible.

Here is the Drought Monitor released last Thursday from the USDA and NOAA. There are many in from Arkansas and northeast of there that hope the path of Isaac (once onshore) pans out, as they would then get some much needed rains. Typically when we have a drought, one of the best ways to bust it is with a tropical system. Here’s hoping that when we see an updated map on September 6th that we see the rains were beneficial. (There will be a new Drought Monitor released on August 30th, but the only rains from Isaac it will include are those that have fallen in Florida through Tuesday morning).

Another threat with a land-falling system is always tornadoes. You can read more about tornadoes that have previously occurred with northern Gulf of Mexico land-falling systems via ustornadoes.com. Already a Tornado Watch is out for areas including Pensacola, Mobile, Biloxi, and New Orleans.

 

The models show consensus on landfall in the New Orleans area, however you can see a few models take the storm into Texas afterwards instead of to the north. These models likely have the ridge not building back in to the north, therefore allowing the system to continue to the northwest. (Graphic via weatherbellmodels.com)

Gulf Coast Impacts

Below are some graphics from the New Orleans and Mobile offices of the National Weather Service, showing what they are expecting (click on the links in this sentence for more from those offices):

State of Emergency


Many have already evacuated the region, and time is quickly running out for people to prepare, evacuate, or go to storm shelters. The Red Cross has set up a map that shows open shelters for people to take refuge from the storm.

 

Google has also set up a map showing the very latest on the storm, including shelters, evacuation zones, webcams, and youtube videos.

You can also keep up-to-date with the very latest by watching our live stream on the WeatherNationTV homepage, just click on the red tab that says “Live” next to the video feed. You can also watch our headline segments and the weather forecast for each region on the home page.

And we would also love to see your videos and photos of the storm, of evacuations in your area, and of preparations being made in your area — of course, only if you can do it safely! Your safety is ALWAYS our number one concern here at WeatherNation. If you do so, you can upload them to the WeatherNationTV website by clicking here. You can also post them on our Facebook page, on Twitter, or upload them via our app for iOS devices (like the iPhone). You can help tell the story of how Isaac is affecting your area!

Isaac vs. Katrina from space

Check out this comparison the Wall Street Journal put together of satellite images from both storms. You can tell Isaac is definitely not as well put together as Katrina. However, remember that the shape of the system and the winds associated with it is not the whole story. The heavy rains and storm surge can be worse at times than the actual winds, as noted above. Just because the storms aren’t the same doesn’t mean Isaac’s impacts won’t be destructive!

We’ll continue to update you with the very latest — stay with WeatherNation!


Meteorologist D.J. Kayser
Follow me on Twitter at: @weathrlver

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