The 2004 Atlantic Hurricane Season and Beyond Chris Landsea NOAA/Hurricane Research Division Miami, Florida, USA January and February 2004 Southern Region Marine Workshop

Why have hurricane damages gone way up? How have hurricanes changed in the past? What environmental factors control hurricanes? What will the next couple decades bring? How is seasonal hurricane forecasting done? How well did the forecasts do in 2003? What is expected at this point for 2004? Outline

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Florida Coastal Population

NORMALIZED DAMAGE is estimated economic damages if past storms made landfall with present-day societal conditions. ND = f(inflation, population, wealth) Source: Pielke, Jr., R. A., and C. W. Landsea, 1998: Normalized Hurricane Damages in the United States: Weather and Forecasting, 13:

Atlantic Multidecadal Mode Local Correlation of SST versus REOF Mestas-Nunez and Enfield (1999)

U.S. MAJOR LANDFALLING HURRICANES: Major East Coast Hurricanes Active Decades Inactive Decades

Coverage of Low Tropospheric Vertical Wind Shear

Strong ConveyorWeak Conveyor

Global Warming versus Society Changes: Hurricane Damages

Dr. Bill Gray Colorado State University

Sea Surface Temperatures

La Nina versus El Nino Hurricane Probabilities La Nina Hurricane RiskEl Nino Hurricane Risk

The “Global Mode”: Enhanced 200mb Subtropical Ridges

“Global Mode”: Winter ’98-’99 To ’99 Hurricane Season

“Global Mode”: Winter ’96-’97 To ’97 Hurricane Season

NOAA Forecast Methodology 1) Assess state of Global Mode currently; 2) Determine probabilities of active/near-average/quiet, given persistence of conditions through season; 3) Adjust probabilities depending upon anticipated Atlantic Multidecadal Mode and El Nino-Southern Oscillation phases For example: Early August 2001 indicated a “near-average” global mode; This would typically suggest: 25% active/50% near-average/25% quiet; After stratifying for WARM Atlantic Mode and neutral ENSO: 40% active/40% near-average/20% quiet.

NOAA: 2003 Atlantic Hurricane Outlook 7 August, 2003: There is a 35% probability of a near-normal Atlantic hurricane season in 2003, a 60% probability of an above-normal season, and a 5% chance of a below-normal season… La Nina has not developed as expected. Nonetheless, the expected conditions combined with the active phase of the Atlantic multi-decadal signal are conducive to an above- normal Atlantic hurricane season … Historical data for similar climate conditions indicates a likely range of tropical storms this season, 7-9 hurricanes, and 3-4 major hurricanes. 19 May, 2003: There is a 35% probability of a near-normal Atlantic hurricane season in 2003, a 55% probability of an above-normal season, and a 10% chance of a below-normal season… This outlook reflects the ongoing multi-decadal conditions, combined with a 70% chance of La Niña, both of which are conducive to increased activity during the normal peak (August-October) of the hurricane season. … The 2003 outlook calls for tropical storms, with 6-9 becoming hurricanes, and 2-4 becoming major hurricanes.

Hurricane Isabel 18 September 2003

Active Decades ACE = TS, 6.5 H, 3 MH Above Normal Season Near Normal Below Normal Season Historical Perspective: ACE Index Atlantic Basin Main Development Region Active Decade ACE = TS, 8 H, 3.6 MH IN-active Decades ACE = 65 9 TS, 5 H, 1.5 MH 2003 Predicted Range

Tropical Storms ACE Index Hurricanes Major Hurricanes Forecast Range Observed Green bars show climatological mean and ACE range for near-normal season (76%-120% of Median) NOAA Seasonal Atlantic Hurricane Outlook May Forecast vs. Observed:

NOAA Seasonal Atlantic Hurricane Outlook August Forecast vs. Observed: Forecast Range Observed Green bars show climatological mean and ACE range for near-normal season (76%-120% of Median) Tropical Storms ACE Index Hurricanes Major Hurricanes

The “Global Mode” – January 2004

Global Ocean Temperature Anomalies

El Nino Forecasts For 2004 El Nino La Nina

Why have hurricane damages gone way up? How have hurricanes changed in the past? What environmental factors control hurricanes? What will the next couple decades bring? How is seasonal hurricane forecasting done? How well did the forecasts do in 2003? What is expected at this point for 2004? Outline