Latest models: Growing risk “Hurricane” Isaac targets Florida

Tropical Storm Isaac continues to organize today in the Atlantic

Hurricane Hunters flying missions into Isaac today

NHC: Isaac likely to reach hurricane strength by tomorrow

Tight Grouping: Models remarkably consistent on focusing track near Florida Monday

Outlier: European the “left most” model takes Isaac into central Gulf of Mexico

Tampa Nightmare Scenario? Latest GFS runs favor a “Tampa direct hit” Monday night

33 Isaac IR.gif

Source: NOAA

Isaac Increases Florida Focus:

Even after 25 years of forecasting weather there are still times when the models shock me. Today is one of those days.

The latest model runs paint an increasingly bad picture for Florida and the possibility of a direct hit from a Category 2 or higher Hurricane Isaac Monday & Tuesday.

With each passing model run the risk grows for the Sunshine State. Here’s some of my latest thinking on today’s trends.

Remarkable continuity in hurricane tracks:

I can’t remember seeing models so tightly grouped 5 days out with a potential hurricane track. The vast majority of models come up with the same solution: Hurricane Isaac will cross somewhere over Florida Monday & Tuesday, then probably curve up the east coast.

33 tracks.png

Source: http://derecho.math.uwm.edu/models/al092012.png

The outlier? The European Model, which steers Isaac into the Gulf, a more westward track. At this point, NHC thinks the GFS and other models have it right.

THIS DEVELOPING WEAKNESS IN THE RIDGE SHOULD ALLOW ISAAC TO TURN NORTHWESTWARD ACROSS EASTERN AND CENTRAL CUBA BY DAYS 4 AND 5. THE NHC MODEL GUIDANCE IS IN EXCELLENT AGREEMENT ON THIS EVOLVING SCENARIO WITH THE ECMWF BEING THE LEFTMOST OF THE MODELS…AND THE GFDL AND HWRF BEING THE RIGHTMOST OF THE MODELS. GIVEN THE RUN-TO-RUN CONSISTENCY OF THE GFS AND UKMET MODELS…MORE WEIGHT HAS BEEN PLACED ON THOSE SOLUTIONS…ESPECIALLY SINCE THEY HAVE A STRONGER AND VERTICALLY DEEPER CYCLONE DEPICTED IN THE MODELS.

-A very “costly” track?

I’m sure the weather war rooms at major insurance giants are mobilizing for Florida today.

The forecast models favor tracks and intensity scenarios that produce very “expensive outcomes” for Florida.

The eventual track of Isaac will be critical, but a north-northwest track over part or all of Florida from a category 2 or 3 Isaac is growing more likely by the hour.

This potentially brings damaging winds into play on a line from Miami through Orlando and Tampa…all of Florida’s major metro areas.

If track forecasts hold, we could be taking about the “most expensive” hurricane in Florida history.

Tampa “Nightmare Scenario?”

For years hurricane experts have warned us. Tampa is one of the most vulnerable cities in the USA to a direct hit from a major hurricane.

33 hh Tampa surge.PNG

Source: NOAA “Hurricane Hunters” Facebook page

This will probably (and hopefully) change, but today’s GFS runs paint a very scary picture for Tampa Monday night.

The GFS tracks a very strong hurricane right up Florida’s Gulf Coast with the center of a (possible Category 3?) hurricane just west of Tampa by midnight Tuesday morning.

33 GFS Isaac.PNG

Source: NOAA

If that happens, the storm surge into Tampa Bay could be incredible. The geography of Tampa Bay makes it extremely vulnerable storm surge. A major hurricane with the center just west of Tamps is the scenario forecasts have warned about for years.

If major evacuations are called for, Tampa’s geography makes it almost impossible to get everybody out of town to safer locations. In fact, possible last hour variations in the eventual track of Isaac may make it impossible to tell residents where to evacuate to.

For the sake of everybody in Tampa Monday night, I hope the models are very wrong.

-Prepare now; and hope for changes:

We have friends in the Tampa area and we’re reaching out ot them today.

My advice is simple. Start hurricane preps today, and don’t wait until the weekend. If the path changes, that’s great. If evacuations are called for this weekend it’s going to be increasingly tough to get out of town & get supplies by then.

There is still time for a major shift in the forecast track of Isaac. Let’s hope for the best and prepare for the worst… as they say.

Hurricane Hunters Critical:

One aspect of hurricane science is that track forecasts are generally much more accurate than intensity forecasts.

The forecast models are designed to track storms, but have a much harder time nailing intensity.

Hurricane Intensity fluctuations are rapid and can be extreme. We can get fixes on position easily from weather satellites, but satellite techniques for intensity estimates are less accurate.

33 isaac intensity.png

Source: http://derecho.math.uwm.edu/models/al092012_inten.png

That’s why data from Hurricane Hunter fights are so critical. Aircraft instruments and “dropsondes” provide real time accurate data in hurricane wind & pressure fields, and can pinpoint hurricane intensity.

So called “eyewall replacement cycles” are poorly understood and not well forecast. These cycles change the intensity of hurricanes dramatically in just a few hours.

If you’re looking for some heroes the next few days as Isaac approaches, how about a dedicated group of men & women who fly right into incoming hurricanes?

33 HH.jpg

Source: NOAA

Stay tuned….Isaac may still throw us some curves. But right now it looks increasingly like Florida is at risk for a major blow from Isaac Monday & Tuesday.

PH

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