Thursday, May 31, 2007

Klotzbach Keeps Hurricane Forecast

Phillip Klotzbach and Dr. William Gray have issued their traditional seasonal start hurricane forecast update. Predictions remain essentially the same as in April:
We estimate that 2007 will have about 9 hurricanes (average is 5.9), 17 named storms (average is 9.6), 85 named storm days (average is 49.1), 40 hurricane days (average is 24.5), 5 intense (Category 3-4-5) hurricanes (average is 2.3) and 11 intense hurricane days (average is 5.0). The probability of U.S. major hurricane landfall is estimated to be about 140 percent of the long-period average. We expect Atlantic basin Net Tropical Cyclone (NTC) activity in 2007 to be about 185 percent of the long-term average.
The Colorado State team explains that this year's predictions are based on "a new statistical scheme" that "utilizes a total of only three predictors."
Two of these predictors are derived from sea surface temperature data obtained from the NCEP/NCAR reanalysis. The third predictor is the previous year’s early December prediction of the Atlantic Meridional Mode (AMM).
AMM is an abbreviation for the measurement of sea surface temperature gradients between the northern tropical and southern tropical Atlantic ocean. So, if we read it right, it looks like what Klotzbach and Gray are saying is that for all the hoopla about the complex and difficult business of predicting hurricanes their own forecasts are based on not much more than sea surface temperature data.

Here's what you think you want to know: the Colorado State boys are saying there's an 81% chance of a hurricane hitting the Gulf coast and a 49% chance it will be a Category 3 or worse.




Category 1-2


Category 3-4-5






Entire U.S. (Regions 1-11)

95% (79%)

88% (68%)

74% (52%)

97% (84%)

99% (97%)

Gulf Coast (Regions 1-4)

80% (59%)

64% (42%)

49% (30%)

81% (60%)

96% (83%)

Florida plus East Coast (Regions 5-11)

73% (50%)

66% (44%)

50% (31%)

83% (61%)

95% (81%)

As Klotzbach and Gray caution, however:

[T]hese seasonal forecasts are based on statistical schemes which, owing to their intrinsically probabilistic nature, will fail in some years. Moreover... the probability of landfall for any one location along the coast is very low... .

In other words, this hurricane prediction stuff is still a mug's game. It just not that far removed from roulette.

Prepare for the worst, hope for the best, and study this map of where the hurricane researchers live:

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