1 / 11

Outline

NOAA’s Atlantic Hurricane Season Outlooks By Dr. Gerry Bell Lead Seasonal Hurricane Forecaster Climate Prediction Center/ NOAA/NWS Hurricanes: Science and Society 13 March 2012. Outlooks made in Collaboration with: National Hurricane Center/NOAA/NWS Hurricane Research Division/NOAA. Outline.

lavina
Download Presentation

Outline

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. NOAA’s Atlantic Hurricane Season OutlooksByDr. Gerry BellLead Seasonal Hurricane ForecasterClimate Prediction Center/ NOAA/NWSHurricanes: Science and Society13 March 2012 Outlooks made in Collaboration with: National Hurricane Center/NOAA/NWSHurricane Research Division/NOAA

  2. Outline • Features of NOAA’s seasonal hurricane outlooks • Science behind the outlooks • Tools used to make the outlooks • Summary

  3. Features of NOAA’s Seasonal Outlook Outlooks indicate the expected overall seasonal activity. • Began in August 1998 • Issued late May and early August • Outlooks are probabilistic, include • Probabilities of season type, • Likely (70% chance) ranges of activity • Extensive discussion www.cpc.ncep.noaa.gov/ products/hurricane/ • CAUTION: NOAA’s outlooks are not a seasonal hurricane landfall prediction. All persons in hurricane-prone regions should prepare each and every hurricane season regardless of the outlook.

  4. Measuring Hurricane Season Strength • ACE index measures overall season strength by accounting for the combined number, intensity and duration of tropical storms and hurricanes. • ACE=Sum of squares of maximum sustained surface wind speed (measured 6-hourly) for all named storms while at least tropical storm strength.

  5. Science Behind NOAA’s Seasonal Outlooks • Hurricane season strength is not random. • Seasonal activity reflects an inter-related set of atmospheric and oceanic conditions -- linked to three main tropical climate factors: • El Niño and La Niña; Reflect large year-to-year changes in tropical Pacific Ocean temperatures. • Year-to-year changes in Atlantic sea-surface temperatures • Tropical multi-decadal (25-40 year) signal : Reflects fluctuations in West African monsoon strength and Atlantic sea surface temperatures. • NOAA’s seasonal outlooks are based largely on these climate factors.

  6. Typical Conditions Associated withActive Atlantic Hurricane Seasons This inter-related set of conditions has strong links to tropical climate factors. CPC has an extensive monitoring program to assess and predict these conditions and the associated climate factors. www.cpc.ncep.noaa.gov/products/hurricane/

  7. El Niño and La Niña • El Niño and La Niña reflect large year-to-year changes • in tropical Pacific Ocean temperatures. Increased Wind Shear, Fewer Hurricanes Decreased Wind Shear, More Hurricanes El Niño La Niña Less Shear More Shear Warm, Wet Cool, Dry El Niño suppresses hurricane activity by increasing the vertical wind shear. Strong wind shear can prevent hurricanes from forming, and can also kill an existing hurricane. La Niña favors more hurricane activity by decreasing the vertical wind shear. www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

  8. Tropical Multi-Decadal Signal Associated with Atlantic High-Activity Era Warmer Stronger West African Monsoon Warmer Drier This climate pattern lasts 25-40 years, and produces key ingredients of a high-activity era for Atlantic hurricanes: warmer waters, reduced wind shear, and favorable winds that strengthen cloud systems coming from Africa.

  9. Tools used to MakeNOAA’s Seasonal Hurricane Outlook • Outlook is subjective blend of statistical and dynamical model forecasts. • Two Step Process: • Step 1: Predict the key climate factors using observations and a suite of different statistical and dynamical models. • Step 2: Predict activity likely to result from predicted climate conditions • Statistical regression and analogue techniques, • New NCEP dynamical model that produces direct hurricane counts. Plot showing model seasonal forecast of tropical storm tracks

  10. Example Showing One Way to Combine Predicted Climate Factors to Make a Hurricane Outlook Hypothetical Prediction of El Niño/ La Niña Example Model Sea-Surface Temperature (oF) Seasonal Forecast Made Before the Season Predicted Strength La Nina El Nino Predicted Average SST Departure is +0.5oF Colder Warmer -6 -4 -2 -1 -0.4 0.4 1 2 4 6 Atlantic SST Departure (oF) This prediction calls for a La Nina to develop Table shows seasonal hurricanes as a function of El Niño/La Niña and Atlantic sea surface temperatures. Based on statistical regression equation developed for Atlantic high-activity era. La Nina El Nino Strength

  11. Summary • NOAA’s Atlantic hurricane season outlooks indicate expected overall seasonal activity . They are not a landfall forecast. • There is a strong scientific basis for making these seasonal outlooks. • Tropical climate patterns controlling seasonal hurricane activity are often predictable. Therefore, seasonal activity is predictable. • Extensive ongoing monitoring, assessment, model development efforts. • The current Atlantic high-activity era began in 1995. Historically these last 25-40 years. • Hurricane preparedness is the most important thing one can do to minimize impacts if a tropical storm or hurricane strikes. All persons in hurricane-prone regions should prepare each and every hurricane season regardless of the outlook.

More Related