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Institute for Crisis, Disaster, and Risk Management Crisis and Emergency Management Newsletter Website |
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April
2004
Volume 6
- Number 3 |
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Related Sites:
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Dr. Gray’s Hurricane Forecasts by Bev Burton If hurricanes and devastation cannot be averted, why make predictions?
Accurate hurricane warnings, if heeded, save lives. Reliable long-term predictions enable residents to take protective measures wrt their residential and business possessions and properties. Dr. William (Bill) Gray, has been at Colorado State University (CSU) 43 years, in meteorology 50 years. He extrapolates past environmental conditions into future predictions. He leads CSU’s Tropical Meteorology Project and focuses on global impacts. His hurricane predictions originated in 1984; only in last 20 years was there sufficient global data. http://www.collegian.com/vnews/display.v/ART/2003/12/09/3fd55cfb6a1ec Namias and Ballenzweig provided the first significant hurricane predictions in the 1950s. They compared mean atmospheric flow fields in the Atlantic Basin. Dr. Gray inverted their method, and used hurricane activity as the dependent variable, linking the number of hurricanes to known tropical phenomena, e.g., Quasi-Biennial Oscillation (QBO), El Nino, Caribbean sea-level pressure anomalies (SLPA) and West African rainfall. Predictions are based on linear regression analysis, and give forecasts for nine separate categories of hurricane activity: Named Storms (NS) Named Storm Days (NSD) Hurricanes (H) Hurricane Days (HD) Intense Hurricanes (categories 3-5 account for 80-85% hurricane damage in US) (IH) Intense Hurricane Days (IHD) Hurricane Destruction Potential (HDP) Potential Destruction (MPD) Net Tropical Cyclone Activity (NTC) http://www.bbsr.edu/rpi/meetpart/092195summary/JE092195summary.html http://hurricane.atmos.colostate.edu/Forecasts/index.php His forecasts range 15 – 40 pages, with a synopsis and a summary of statistical probabilities, before it delves into the technical details (detailed methodology). NOAA annual hurricane season predictions report them as “average,” “above” or “below average,” with only a brief description and cite no methodology. Consequently media rarely utilizes Nona’s predictions in their public broadcasts. Dr. Gray’s hurricane prediction is a series of reports starting in December prior to the next calendar year’s hurricane season, with updates in April, June and August. Forecast report contains: 1. Overall Prediction – represents what is reported to the public (includes statistical, analog, and qualitative adjustments) 2. Statistical Method – combines climate factors into a formula of predetermined coefficients to produce the nine forecast elements. The factors fall into three main categories: Quasi-Biennial Oscillation, Africa, and El Nino-Southern Oscillation. 3. Analog Method – Dr. Gray chooses six factors, which will pose the most influence over the upcoming hurricane season, then searches for past years with actual similar values. These years are analog years. Five analog years are chosen for comparison and the observed parameter values are averaged to produce a prediction for the upcoming season. Qualitative Adjustments include additional factors: sea surface temperatures, trade winds, and the Atlantic Thermohaline cycle (single most important factor in determining the number of intense hurricanes in a season). Atlantic Thermohaline cycle was not understood until the mid-90’s. Dr. Gray connected Atlantic basin hurricane activity with this cycle, spearheading new research. Long-term Hurricane Season Predictions http://web.nwe.ufl.edu/~jdouglas/final15581.pdf http://web.new.ufl.edu/~jdouglas/final1558proposal2.pdf Dr. Gray predicts over the next 20 years “We’ll see hurricane damage like we’ve never seen before.” He does not attribute this upward swing to global warming. Rather, hurricane activity has its own natural, 20-40 year cyclical nature which has occurred for thousands of years. NOAA, has stopped funding his research, as no longer needed or no longer ground breaking, all 13 of Dr. Gray’s grant requests since ‘91 were turned down (likely a backlash due to his criticism of NOAA’s global warming theories). http://www.globalwarming.org/sciup/sci12-8-99.html http://www.wildweather.com/mom/gray.htm Predictions vs. Actual Table Attached (1984 – 2002):
http://www.aoml.noaa.gov/hrd/tcfaq/F5.html
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