1A.1 Thirty Years of Making Atlantic Seasonal Hurricane Forecasts - Lessons Learned, Certitudes Abandoned

Monday, 31 March 2014: 8:15 AM
Pacific Ballroom (Town and Country Resort )
William M. Gray, Colorado State Univ., Fort Collins, CO

Handout (4.4 MB)

It's possible to make empirical seasonal hurricane predictions that are superior to climatology in the majority of years. The earth's climate system has, surprisingly, a number of pre-hurricane season predictive signals that can be utilized to tip-off how active the coming season is likely to be. But it isn't easy and the precursor signals that we use that work very well over 25-50 years can mysteriously stop working and sometimes even reverse themselves.

I and my longtime colleague (Phil Klotzbach) and former CSU colleagues (C. Landsea, J. Knaff, and E. Blake) in this venture have shown that we can predict up to 50-60% of the seasonal hurricane variability over many years. But there are years when the other 40-50% of the unknown hurricane variance is dominant and our forecasts can occasionally go badly off target (i.e. 1997, and 2013). Nothing documents one's incompetence better or is more imprinted in one's colleagues minds more deeply than a bad forecast bust.

But you always learn more about how the atmosphere functions when you bust than when you verify. Our large bust of 2013 has brought home to us the need to very closely monitoring of the Atlantic Ocean Thermohaline (or AMO) Circulation (THC).

But the primary question remains, “Is it better to have forecast and busted than to have never made a forecast at all?”

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