Gulf Coast Preparations Should Begin Now For Isaac

Preword: Do not take the following information as official information. Always disregard other sources in place of government warnings and advice. The following is meant as advice, but is not intended, in any way, to replace NHC forecasts and warnings. Use the following info at your own discretion.

"It's never too early to prepare. Now is the time."

Todays new model forecasts brought in a wide array of solutions, many now hitting the Florida Panhandle rather than affecting the East Coast head-on. What you see above is the European's ECMWF model, recognized as one of the, if not the best, forecasting models out there. Today's forecast off the ECMWF model proved interesting, with a 963 millibar major hurricane slamming into southwest Louisiana/far east Texas. I am not saying it will happen, nor am I saying it will not happen. However, the potential appears to be there.

We are watching a disturbance push its way to the east off the coast of the eastern United States. As you can see, the arrows on the lines show a northeast movement, and this could very well enhance Isaac's track. However, note that the disturbance is largely over the Atlantic and far from Isaac, reducing the potential for a sudden northeast turn that would possibly landfall upon the East Coast.
I want to make it clear that, should the current model consensus hold up, the system would landfall on the Florida Panhandle, move north (and possibly east), and may re-emerge into the Atlantic, where additional landfalling on the East Coast states may occur. However, at that point, Isaac will have dramatically weakened.

 The most recent model guidance as of 18z today shows a general consensus taking Isaac into the Gulf of Mexico and hitting either in the Panhandle of Florida, or more into the central Gulf Coast. Because I don't know these models as well as I do the global ones (GFS, ECMWF), I am not confident giving an assessment on the track. However, if I were to speculate, I would say that the continued westward progression with little north progression is edging the models west, as they should.

As of roughly 20z today, the center of Isaac was observed at roughly 16N longitude and 67W latitude. What I care more about is the longitude. Because Isaac remains in the general 15-17N realm, I cannot see any East Coast forecast models working out. Even a scrape with western Florida is edging out of the question. It is now up to Isaac to either strengthen and get going, or remain weak and disorganized and possibly not make it up to the status the ECMWF is projecting.

Andrew

ECMWF Slams Isaac Into Gulf Coast as Major Hurricane- Why You Shouldn't Count It Out

The 12z ECMWF run today took Tropical Storm Isaac, bombed it out again in the Gulf of Mexico, and slammed Isaac into the Gulf Coast as a major hurricane, with a central pressure of 964 millibars.

Many have been discounting this system as an outlier, and this continues, even as this is not the first time the bombing-out solution has been shown with Isaac. A very similar solution and slightly different track was shown yesterday by the ECMWF.

Now, it's a model war, like the ones we will see in winter: ECMWF vs. GFS for Isaac's track. Let's look at a major component of the track.

In this map, we can see Isaac just about to enter the Caribbean. But notice the large disturbance creating quite a commotion along the East Coast. The models are interpreting this differently. As you can see by the arrows in the dark red off the East Coast, the direction the winds are going is northeast, hence the East Coast-threat tracks being shown by other models.
The question is if the disturbance's influence will be enough to force Isaac north and take an East Coast-threatening track, like the GFS and others say, or will the system be able to pass by the strong northeast winds and pass into the Gulf of Mexico, where a dangerous scenario could unfold, as the ECMWF describes.

I did some deep digging and came upon an observation chart for 12z at 250mb. I also found the 12z GFS' 12z initialization chart at 250mb. I compared the two, and found slightly stronger winds in the GFS' forecast. While it may not seem huge now, the implications could be massive in the long range.

Now, let's check out the 2010 and 2011 model performance statistics for the Atlantic. We will start with 2010.

On the right sidebar is the skill percentage of the models, while the bottom bar has the forecast hour. If we look on the graph and find a light blue line leading the pack in skill, we look to the right and see it is the EMXI model, also known as the ECMWF. This shows that the ECMWF led the model forecasting skill for 2010. While a slight lapse may have occurred towards hour 120, the skill remains at the highest notch.

Moving on to 2011.

In 2011, we see a worse performance by the bottom forecasting models, and a tight race for the best forecasting model for 2011. If we look closely, we see the ECMWF and NHC forecasts tied in the early forecasting hours. But they both dropped off going into hour 120. Here's the thing- the EMXI model (ECMWF) dropped off just a little less than the NHC, showing that the ECMWF emerged victorious for best model track skill.

So, now with two runs of a major Gulf Coast threat under its belt, along with two best model track skill awards, one can not help but wonder if the ECMWF is correct in the assumption that the Gulf Coast is indeed at risk. I, for one, like to keep all options on the table. Frankly, I think the ECMWF is correct, and past analogs with a similar situation as Isaac think so too...

Climatologically, more systems in Isaac's position tend to go into the Gulf of Mexico and make landfall in that area, rather than hitting the East Coast. This is a dramatic shift from a very short time ago, when more analogs were pointing to an East Coast run than the Gulf of Mexico. Time will tell, but this is just another piece to add to the puzzle.

Andrew

Burst of Convection At Isaac's Center

A burst of convection has been observed both on infrared and microwave imagery, providing some evidence for possible strengthening in Isaac.
A recent northwest movement was also observed, and this could dampen hopes of a landfall in or entering the Gulf of Mexico.
I will post another update this afternoon.

Andrew

Charleston, Myrtle Beach Devastated by Isaac in GFS Individual Ensemble Forecast

A member of the 12z GFS Ensembles is showing a solution that would devastate Myrtle Beach and Charleston. This member shows a very strong hurricane slamming into the Southeast and possibly providing mass flooding and a preceding mass exodus, should this threat become real.

However, realistically, this possibility is very very low. That's why we also have a mean forecast of these individual ensemble forecasts. This is more of a for-show piece, but also demonstrates the potential that Isaac now has, and just what it ends up doing is very uncertain after what the ECMWF put out today, and that is shown below.

At Hour 240, the ECMWF is projecting a 961mb hurricane moving towards the Gulf Coast. Because rapid intensification will have been ongoing to this point, it is very possible that such intensification continues. From then, landfall could likely occur from Louisiana eastward. The ECMWF Ensembles are not as eager, but do show a system entering the Gulf of Mexico, and this could very well get aggressive very, very fast.

More on this will be available tomorrow.

Andrew

BREAKING: Tropical Storm Isaac Forms

Reconnaissance data from aircraft investigating Tropical Depression NINE have sent back information that shows many instances of tropical storm winds being observed, including one wind speed calculated at 44 MPH.

This means that the next National Hurricane Center update will most likely certify this as Tropical Storm Isaac. I will have an evening post up and out later on.

Andrew