2015 ATLANTIC HURRICANE SEASON: TROPICAL STORMS ANA AND BILL RUSH IN ON EXPECTED QUIET SEASON The 1957 and 1965 seasons were both moderate El Niño seasons and saw major hurricane landfalls with Audrey (1957) and Betsy (1965). As with any season, a landfalling hurricane a catastrophic hurricane landfall. generally south of 20oN. The 1957 and can be a serious threat regardless of Landfalls are determined by weather 1965 seasons were both moderate El seasonal outlooks for the Atlantic Basin patterns during a hurricane’s lifetime, Niño years, but witnessed the landfall at large. not pre-season estimates of hurricane of major hurricanes — Audrey (1957) frequency. The recent landfall of Tropical and Betsy (1965). The 1957 season For the North Atlantic Basin, seasonal Storms Ana and Bill stands as a reminder experienced only three hurricanes in the outlook providers are expecting tropical to this point. Atlantic Basin at large and Audrey was activity to fall below the long-term the only one of the three to make U.S. average of 1955-2014. Common factors Indeed, much of the Atlantic Main landfall. Audrey formed in the Gulf of include a continuing El Niño and cool Development region currently carries Mexico and made landfall as a notorious sea-surface temperatures (SSTs) in the cooler sea-surface temperatures, but the Category 4 hurricane near the Texas- Atlantic Main Development Region waters of the northern Caribbean and Louisiana border. (AMDR) (the area of the tropical Atlantic northern Gulf of Mexico are warmer than between Africa and the Gulf of Mexico, average. Tropical storm development While we indeed may see a quiet season, specifically 10oN-20oN and 20oW-85oW). close to the mainland carries a higher warm waters in the northern Gulf of chance of landfall. Mexico and northern Caribbean warrant Historically, it is clear that the relationship a moment of pause. As with any season, between basin activity and landfalls is Also, it is accepted that El Niño landfall is a possibility and warrants very volatile. Greater Atlantic activity conditions tend to suppress hurricane review of hurricane plans and procedures does not necessarily equate to more development in the Atlantic Basin, but by both property owners and the (re) tropical storm landfalls, just as a quiet scientific research reveals that this effect insurance industry alike. season does not guarantee safety from is strongest in the deep tropics, and 1 2015 SeasONAL OUTLOOKS F-F-11 || U.S. LANDFALL Landfall TO BASIN TO B RATIOasin –R DETECTEDatiO – DETECTED HURRICANES H (1URRICANES900-2014) (1900-2014) F-3 | SEA-SURFACE TEMPERATURE ANOMALIES AS OF MAY 25, 2015 T-1 | SEASONAL OUTLOOKS FOR THE 2015 ATLANTIC HURRICANE SEASON SUGGEST REDUCED Named Major 100 Source Hurricanes8 A.C.E.10 Basin ACTIVITY Storms7 Hurricanes9 Post-War Satellite Development Near United States Still Aerial Detection Detection WSI1 (May 26) 9 5 1 - Possible – U.S. Landfalls Uncertain 80 CSU3 (June 1) 8 3 1 40 4 As illustrated in Figure 1 (right), the historical UK Met (May 21) 8 5 - 74 proportion between basin counts and 60 NOAA5 (May 27) 6-11 3-6 0-2 37-79 ) landfalls has been very volatile on an annual NCSU2 (April 16) 4-6 1-3 1 - 6 basis. There is only a weak correlation Ratio (% 1995-2014 Mean 14.8 7.6 3.5 131 40 between hurricane counts in the Atlantic 1955-2014 Mean6 11.2 6.1 2.5 100 Basin and the number of U.S. landfalls. The statistical significance is a subject of some 20 1 Weather Services Incorporated/The Weather Channel 2 North Carolina State University. (Xie et. al.,2015) debate in the scientific community (Coughlin 3 Colorado State University (Klotzbach, Gray) 4 U.K. Met Oce, 2015: North Atlantic tropical storm seasonal forecast 2015. et al., 2009; Dailey et al., 2009). http://www.metoce.gov.uk/weather/tropicalcyclone/seasonal/northatlantic2015. Accessed May 2015. 0 5 Climate Prediction Center of the National Oceanic and Atmospheric Administration (NOAA) 6 Hurricane Research Division (NOAA) 15 0 00 10 20 25 30 35 40 45 50 55 60 65 97 75 80 85 90 95 00 05 010 19 1905 19 19 19 19 19 19 19 19 19 19 19 19 1 19 19 19 19 19 20 20 2 7 Tropical cyclone with maximum sustained surface winds of at least 39 mph Source: Guy Carpenter 8 Tropical cyclone with maximum sustained surface winds of at least 74 mph 9 Hurricane with maximum sustained surface winds of at least 111 mph (Category 3 or higher on the Sar-Simpson scale) Note declining trend over time with post-war overflight detection (late 1940s) and satellite detection (1970s). Source: Oce of Satellite and Product Operations (NOAA) 10 Accumulated Cyclone Energy (or A.C.E.) is defined as the sum of squares of six-hourly maximum sustained wind speeds (in knots) Note variability from year to year and high ratio in 1985. Note the patches below normal in the deep tropics. for all tropical storms or hurricanes. Units are x104 knots2. This index is a proxy for the energy expended by a tropical cyclone. Note the area above normal near the southeast U.S., northern Caribbean and Gulf of Mexico. The year to year volatility warrants preparation Factors of greatest influence include: The predictions of seasonal outlook for any season. The quiet 1992 season saw providers, including the Colorado State 1. A moderate El Niño expected through the only four hurricanes with one making a very University team of Professors William A. 2015 hurricane season. impactful and historic U.S. landfall. Meanwhile, Gray and Phillip J. Klotzbach, are included the 2010 season saw 19 named storms and 2. Cooler than normal SSTs in the AMDR. in Table 1 below. 12 hurricanes, without a single U.S. landfall. In T-1 | SEASONAL OUTLOOKS FOR THE 2015 ATLANTIC HURRICANE SeasON 1985 there were seven hurricanes in the basin, Named Major and six of these made U.S. landfall (some of Source Hurricanes8 A.C.E.10 Storms7 Hurricanes9 which were very impactful). 1 Seasonal activity predictions for the basin WSI (May 26) 9 5 1 - are valuable, but the impacts of even a single CSU3 (June 1) 8 3 1 40 tropical storm or hurricane landfall (quiet UK Met4 (May 21) 8 5 - 74 season or not) can be quite severe. Historical experience warrants proper review and NOAA5 (May 27) 6-11 3-6 0-2 37-79 preparation of hurricane plans by all interests NCSU2 (April 16) 4-6 1-3 1 - from individual homeowners to businesses to 1995-2014 Mean6 14.8 7.6 3.5 131 the (re)insurance industry at large. 1955-2014 Mean6 11.2 6.1 2.5 100 In light of this reality, seasonal outlook providers expect 2015 basin counts to fall 1 Weather Services Incorporated/The Weather Channel below the long-term mean of 1955-2014. 2 North Carolina State University. (Xie et. al.,2015) 3 Colorado State University (Klotzbach, Gray) The expected counts also fall clearly below 4 U.K. Met Office, 2015: North Atlantic tropical storm seasonal forecast 2015. http://www.metoffice.gov.uk/weather/tropicalcyclone/seasonal/northatlantic2015. Accessed May 2015. the short-term 1995-2014 mean, reflecting 5 Climate Prediction Center of the National Oceanic and Atmospheric Administration (NOAA) the current warm phase of the Atlantic 6 Hurricane Research Division (NOAA) 7 Tropical cyclone with maximum sustained surface winds of at least 39 mph Multidecadal Oscillation. 8 Tropical cyclone with maximum sustained surface winds of at least 74 mph 9 Hurricane with maximum sustained surface winds of at least 111 mph (Category 3 or higher on the Saffir-Simpson scale) 10 Accumulated Cyclone Energy (or A.C.E.) is defined as the sum of squares of six-hourly maximum sustained wind speeds (in knots) for all tropical storms or hurricanes. Units are x104 knots2. This index is a proxy for the energy expended by a tropical cyclone. 2 F-4 | HURRICANE AUDREY (1957) F-5 | HURRICANE BETSY (1965) SOURCE: Guy Carpenter with data from HURDAT 2 (Hurricane Research Division/NOAA) SOURCE: Guy Carpenter with data from HURDAT 2 (Hurricane Research Division/NOAA) F-2 | AVERAGE SEA-SURFACE TEMPERATURE ANOMALIES FOR THE PACIFIC BASIN Source: Climate Prediction Center (NOAA) Note the warm pool near 0o N by 180o W and warmer waters centered along the equatorial regions of the East Pacific. F-1 | U.S. LANDFALL TO BASIN RATIO – DETECTED HURRICANES (1900-2014) F-3 | SEA-SURFACE TEMPERATURE ANOMALIES AS OF MAY 25, 2015 T-1 | SEASONAL OUTLOOKS FOR THE 2015 ATLANTIC HURRICANE SEASON Named Major Source Hurricanes8 A.C.E.10 100 Storms7 Hurricanes9 Post-War Satellite Aerial Detection Detection WSI1 (May 26) 9 5 1 - 80 CSU3 (June 1) 8 3 1 40 UK Met4 (May 21) 8 5 - 74 60 NOAA5 (May 27) 6-11 3-6 0-2 37-79 ) NCSU2 (April 16) 4-6 1-3 1 - 6 Ratio (% 1995-2014 Mean 14.8 7.6 3.5 131 40 1955-2014 Mean6 11.2 6.1 2.5 100 20 1 Weather Services Incorporated/The Weather Channel 2 North Carolina State University. (Xie et. al.,2015) 3 Colorado State University (Klotzbach, Gray) 4 U.K. Met Oce, 2015: North Atlantic tropical storm seasonal forecast 2015. http://www.metoce.gov.uk/weather/tropicalcyclone/seasonal/northatlantic2015. Accessed May 2015. 0 5 Climate Prediction Center of the National Oceanic and Atmospheric Administration (NOAA) 6 Hurricane Research Division (NOAA) 15 0 00 10 20 25 30 35 40 45 50 55 60 65 97 75 80 85 90 95 00 05 010 19 1905 19 19 19 19 19 19 19 19 19 19 19 19 1 19 19 19 19 19 20 20 2 7 Tropical cyclone with maximum sustained surface winds of at least 39 mph Source: Guy Carpenter 8 Tropical cyclone with maximum sustained surface winds of at least 74 mph 9 Hurricane with maximum sustained surface winds of at least 111 mph (Category 3 or higher on the Sar-Simpson scale) Note declining trend over time with post-war overflight detection (late 1940s) and satellite detection (1970s).