KARL Sends a Reminder

Sep 17, 2010 - Louisiana has been lucky so far.  Very lucky.

After what seemed like a slow start to the 2010 Hurricane Season, some were dismissing "active season" projections released in May and June and suggesting that the gloomy forecasts were proving to be "false alarms."

Not so fast, armchair experts! While it is true that we didn't have a gangbuster's outbreak of storms in June and July, the season was "near average" through much of the first three months (June-thru-August) in terms of activity and storm numbers.

Apparently, Mother Nature decided to ease her way into Atlantic activity this year.  We are now well-ahead of "average storm numbers" for this time of year: 11 'named' storms as of mid-September, thanks to a busy run over the last four weeks.  Since August 22nd we have added 8 'names' to the season – 5 of those since September 1st. Of those 8 'named' in the last four weeks, 5 became hurricanes -- and all 5 achieved 'major' hurricane intensity, with 4 reaching Category 4!

And the Gulf has been far from quiet as well. Karl is the 4th 'named' storm in the Gulf (the long-term "average" for the entire season is three), including two -- Alex and Karl -- as hurricanes.  Add two 'almosts' -- TDs #2 and #5 -- and there can be no arguing that the Gulf has been busy as well.

Virtually every significant measure of activity, with the exception of U.S. landfalls, is above-average for this time of the season. Thus far, the U.S. has fared fairly well: let's all knock on wood.

The only direct landfall thus far was over south Florida by T.S. Bonnie back in July. A sideswiping, beach-pounding Earl had almost the entire Atlantic Seaboard on pins-and-needles, and we can't forget about the record and near-record rains and resulting floods over portions of Texas and Oklahoma as a result of T.S. Hermine. But given some of the gloomy outlooks at the start of this season, we seem to be doing better than expected.

So … back to Karl. What can we learn from Karl as he takes aim on the mainland coast of Mexico?

The number one story here -- in my opinion -- is how far we remain from skillful predictions of tropical system intensification. Just a few days ago, hurricane specialists were debating, "would Karl be over water long enough to reach hurricane strength before 'his' second landfall, after weakening over the Yucatan and spending only a short time over the Bay of Campeche?"  Answered. Big time.

First, Karl failed to drop below tropical-storm intensity while crossing the Yucatan. Then, once back over water and yet still relatively close to land, Karl displayed steady strengthening, going from a moderate tropical storm to a Category 3 hurricane in just 24 hours!

How did the experts fail to foresee that? Simple. The scientific skill for forecasting changes in tropical system intensity remains rather poor.

In the last 15 to 20 years, forecasting skill on the "where" for tropical systems has improved markedly.  Indeed, the average forecast error as to the track of a storm -- where will it go and how quickly will it get there? -- has been cut in half!  That includes everything from the 24-hour forecast to the two- and three-day projections: all are much better than they were just a decade ago.

But forecasting the "what" --  changes in tropical system intensity -- has not enjoyed comparable improvement with time. The ability to anticipate whether a tropical system will strengthen, weaken, or maintain its current intensity has changed little over the past dozen or so years, and it remains the most elusive of forecasting endeavors.

Why is this so important? For any coastal state, the potential for quick intensification of a storm just hours before landfall means that any system near the coast has the potential to generate substantially greater damage that what may be anticipated. Karl should not be considered as a rare exception: a number of storms in recent years have demonstrated modest to significant strengthening just before making landfall.

Given this potential, it would seem prudent for emergency-management practices and response efforts -- and the family and business "Game Plans" of coastal residents -- to presume a "next category" plan of action for impending landfalls. In other words, act as if a threatening tropical storm is really a Category 1; respond to an impending strike by a Category 1 hurricane as if it were going to be a '2,' maybe even a '3.'

While such a strategy may result in added financial burdens and unnecessary efforts, when it comes to the wind-rain-surge triple threat of tropical weather, I would argue that over-preparedness trumps under-preparedness every time.