Monday, September 5, 2011

What Does the Future Hold for Hurricane Katia?

Infrared (above) and visible (below) satellite images show the large eye of Hurricane Katia well to the South of Bermuda this morning.

As of the 11am EDT National Hurricane Center (NHC) advisory, the center of Katia was located about 500 miles South of Bermuda, and moving toward the Northwest at 13 mph.  Maximum sustained winds were estimated at 110 mph, and the minimum central pressure was 28.50 inches of mercury (965 millibars).

Katia is currently a high-end Category 2 hurricane, and additional strengthening is forecast today.  If this occurs as expected, Katia is likely to become a major hurricane later today or tonight.

The short-term forecast track of Katia remains unchanged, with a continued Northwestward trajectory expected, along with a slight decrease in forward speed as she grows stronger.  This would bring the system out near 30 degrees North / 70 degrees West sometime on Wednesday morning...

It is the forecast beyond midday Wednesday that becomes tricky.  As you can see by the image above, the NHC is forecasting Katia to take a Northward turn late Wednesday and into Thursday, and then a Northeastward turn back out to sea by late Thursday into early Friday.  While the above forecast would take the most significant threats associated with Katia to the East of the U.S., large swells and rip currents would still be likely along the coast from the Carolinas on Northward beginning early Thursday.

The above forecast is generally right down the middle of the current computer model consensus, which is shown by the "spaghetti" map on the image below:

The turn toward the North and Northeast is expected to take place as Katia approaches 70 degrees West Longitude and comes under the influence of a trough of low pressure across the eastern U.S.  This trough, which will be at least partially associated with the remnants of Tropical Storm Lee, is forecast to force Katia to make the "right" turn as the above human and model forecasts depict.

This is the type of trend I've been expecting for the last few days, but with that said, the thing to watch will be the development of the trough and track of the remnants of Lee over the coming few days.  If this doesn't materialize as currently expected, then a more Westward track of Katia would not be out of the question.

Regardless, those with interests along the U.S. East Coast from North Carolina on Northward can expect higher waves and dangerous rip currents by mid to late week.  Hopefully that will be the only impact that Katia has on the U.S., but we need another day or two just to be sure...

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poppypbr said...

Katia will be attracted to (as a matter of physics) and attempt to connect or follow the low pressure center left by TS Lee that is following the stagnant cold front that has approached the east coast. Worst case scenario: Katia will connect with the cold front and TD Lee making landfall as a category 3 as it strengthens moving inland at the Virginia side of Chesapeake Bay. Washington D.C will experience the full right side quadrant brunt of the storm and the storm surge up the Chesapeake and across the Del-Mar Peninsula may be of biblical proportions.

The National Weather service models are based on old paths taken by Hurricanes and Tropical Storms from too long ago to be of any relevant use in todays changing global dynamic. The facts are that very few West Atlantic Huricanes make the "big curve" and most of the recent ones have slammed the east coast: Andrew. Hugo, Bob, etc., etc. Even Irene was very reluctant to make any turn and charged straight into New England instead. Wishful thinking perhaps? Only the paths of the last 10 to 15 years are relevant today.

Rob In Texas said...


Thanks for the comment. I wanted to make a point of clarification on the 2nd portion of your comment...

Not all of the models factor-in the historical tracks of past hurricanes and tropical systems that you suggest. There are 3 types of computer models largely in use today: statistical, dynamical and statistical-dynamical. Only the statistical and/or statistical-dynamical models factor-in the tracks of previous tropical systems (thats where the term 'satistical' comes into play). Dynamical models, such as the GFS model, do not factor-in previous tracks.

With that said, all 3 of the model types are currently forecasting Katia to make a Northward and then Northeastward turn in response to the forecast "steering currents" along the East coast in a couple of days. This trend has actually been forecast with an increasing amount of consistency among all of the models for the past few days now...