NHC_5am

Okay…this morning we are going to focus on Isaac and the ever changing forecast with him.  At the moment, Isaac is still a tropical storm with winds that have increased to 65 mph with a falling central pressure of 995mb.

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

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...
* THE CUBAN PROVINCES OF CIEGO DE AVILA...SANCTI SPIRITUS...VILLA
CLARA...CAMAGUEY...LAS TUNAS...GRANMA...HOLGUIN...SANTIAGO DE
CUBA...AND GUANTANAMO
* THE NORTHWESTERN BAHAMAS
* 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...
* THE CUBAN PROVINCES OF MATANZAS AND CIENFUEGOS
* THE FLORIDA EAST COAST NORTH OF SEBASTIAN INLET TO FLAGLER BEACH

With that being said…there is still a considerable difference with the model spread this morning even in terms of track.  The one thing that does stick out is that the intensity forecasts continue to go up before the storm is forecast to make landfall on the Gulf Coast.  There is an increasing threat that this system will become a major hurricane prior to landfall.

AL09_current

As you can see above, models are beginning to diverge again with the National Hurricane Center currently picking a “middle of the road” path for the system.  The consistent shift over the last 24 hours has been westerly and this will be something key that we will need to watch this afternoon and tonight especially if some of the higher resolution models come to pass. 

Below…is a short term model known as the RAP that we use for hour by hour forecasts…

18hrRAP11z82612

 

As you can see with the RAP model above…by 11PM tonight it has the storm moving DUE westerly.  This is the most extreme westward motion that I can find on the model suite.  It seems to be outside of the entire spaghetti model guidance envelope, but an interesting scenario none-the-less given it’s high resolution grid.  This is something we will keep in mind and monitor because if this were to be correct…it is likely that you would see forecast tracks shift even further west.  Houston…Galveston…Lake Charles…you are not out of the woods yet.

Gulf_SST

Sea Surface temperatures ahead of Isaac in the Gulf are very warm….29-31 degrees Celsius which will make for a good surface environment for strengthening as he moves in a westerly direction.

Gulf_TCHP

This is our tropical cyclone heat potential plot.  This says to me that the waters are very warm at a fairly deep level and we will most likely deal with a strengthening hurricane up to landfall…so I don’t expect this storm to churn up the water enough to cool it down and allow for a steady strengthening storm.  It has the potential to “bomb” out or strengthen rapidly.

GFS_Upper_Shear

This is the 300mb wind level chart off of the GFS valid at midnight tonight.  AS you can see…upper level winds are basically at a minimum over the Gulf of Mexico which is what a hurricane needs to vent and keep it’s outflow pattern.  Increasing winds would allow for very little strengthening due to shearing of the cloud pattern and disrupting the processes of sinking in the core and shearing the intense convection away within the inner core.  However, we don’t look to be lucky enough to have shear present…so this is another reason strengthening is expected up until landfall.  The closest approaching trough of low pressure is off of the west coast of the US and subtropical ridging will continue to fuel the outflow of Isaac.

geo_natl_20120826_0930

Here is a current satellite depiction of Isaac before we throw up a couple of higher resolution model solutions.  He seems to be gaining convection on the north side of his center.  This should begin to wrap around or develop over the center and allow for him to start his strengthening process later today.  Isaac will likely be a hurricane by tonight.

60hrHWRF06z82612

This is the latest HWRF model plot for noon on Wednesday.  You can see this would be a very bad solution for New Orleans.  A powerful hurricane…likely stronger than Katrina at landfall in terms of wind…would plow into southern Louisiana and bring a massive storm surge into the Mississippi sound and Lake Pontchartrain.  This would generate a flooding situation for the New Orleans area again.  At this point, I would go ahead and plan to evacuate ahead of time..as in today.  Things can change with the models, but the current trends are not good for this general area.

78hrGFDL06z82612

This is the GFDL model valid at midnight Wednesday.  As you can see, landfall is about the same location as the HWRF but not quite as strong.  The storm is still strengthening as it comes inland but the surge potential and wind potential would be a bit lower than the previous model.  Still a pretty rough flooding situation for the area.  Also, timing differs on most models by some 12 hours.

72hrEC00z82612

Finally…this is the forecast for 7pm on Tuesday evening from the European model.  It maintains a Florida panhandle landfall around Pensacola.  This model also indicates strengthening up until landfall and this storm could end up being a major hurricane if this model is correct.  This would mean hurricane conditions would be likely from Destin to Mobile with Pensacola getting hammered pretty hard.

All in all…we are expecting a potentially major hurricane landfall along the northern Gulf coast sometime from Tuesday evening through Wednesday evening depending on track.  Also, the potential for large storm surge…flooding rains….destructive winds…and isolated spin up tornadoes in the region.  We still plan to depart this evening…however, we may traverse to Mobile, AL instead of Destin given the current trends.  We will continue to monitor today and make a final decision this evening before posting up a short web video with our plans. 

Everyone be prepared along the northern Gulf Coast.  Supplies are running out and fuel is already limited as shortages have been reported.  Call your local EMA/Sheriffs office to see if shelters are available in your area if you can not leave the threat zone.  We will keep you posted with the latest information as we receive it…

Brett

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