FORECAST OF ATLANTIC HURRICANE ACTIVITY FOR SEPTEMBER AND OCTOBER 2005 FORECAST OF ATLANTIC HURRICANE ACTIVITY FOR SEPTEMBER AND OCTOBER 2005 AND SEASONAL UPDATE THROUGH AUGUST




Following a record amount of June-July tropical cyclone activity and an active August in which Hurricane Katrina caused the greatest economic loss ever inflicted by a hurricane on the United States, we are continuing the bad news by predicting above-average activity for September and October. This year should be one of the most active and is already the most destructive hurricane season on record.


(as of 2 September 2005)




By

William M. Gray1 and Philip J. Klotzbach2



with special assistance from William Thorson3






This forecast as well as past forecasts and verifications are available via the World Wide
Web: http://hurricane.atmos.colostate.edu/Forecasts - also,



Brad Bohlander, Colorado State University Media Representative, (970-491-6432) is available to answer various questions about this forecast.






Department of Atmospheric Science

Colorado State University

Fort Collins, CO 80523

email: barb@tutt.atmos.colostate.edu



ABSTRACT

Information obtained through 31 August 2005 shows that we have already experienced 110 percent of the average full season Net Tropical Cyclone (NTC)4 activity. In an average year, 33 percent of the seasonal average NTC of 100 occurs before the end of August.


Our September-only forecast calls for five named storms, four hurricanes, two major hurricanes and NTC activity of 80 which is much above the mean September-only average value of 48.


Our October-only forecast calls for three named storms, two hurricanes, one major hurricane and NTC activity of 30 which is much above the mean October-only average value of 18.


We anticipate that the 2005 Atlantic basin tropical cyclone (TC) season will be much higher than the full season activity we anticipated in our early December, early April, and early June forecasts. We expect that by the time the 2005 hurricane season is over, we will witness seasonal tropical cyclone activity at near record levels.




2005 ATLANTIC BASIN SEASONAL HURRICANE FORECAST AND END OF AUGUST UPDATE



Full Season Tropical Full Season Observed Forecast Full Season
Cyclone Parameters Adjusted Activity Updated Updated After Adjusted
and their 1950-2000 5 Aug 2005 Through Sept.-only Oct.-only 1 Sep 2 Sep 2005
Climatology (in parentheses) Forecast Fcst. August Fcst. Fcst. Activity Fcst.
Named Storms (NS) (9.6) 20 12 5 3 8 20
Named Storm Days (NSD) (49.1) 95 49 31 13 44 95
Hurricanes (H)(5.9) 10 4 4 2 6 10
Hurricane Days (HD)(24.5) 5518 22 6 28 45
Intense Hurricanes (IH) (2.3) 6 3 2 1 3 6
Intense Hurricane Days (IHD)(5.0) 18 8.25 6 1 7 15
Net Tropical Cyclone Activity (NTC)(100%) 235 110 80 30 110 220




Acknowledgment


We are grateful to the National Science Foundation (NSF) and Lexington Insurance Company (a member of the American International Group) for providing partial support for the research necessary to make these forecasts. We also thank the GeoGraphics Laboratory at Bridgewater State College (MA) for their assistance in developing the Landfalling Hurricane Probability Webpage (available online at http://www.e-transit.org/hurricane).


The first author gratefully acknowledges valuable input to his CSU research project over many years by former graduate students and now colleagues Chris Landsea, John Knaff and Eric Blake. We also thank Professors Paul Mielke and Ken Berry of Colorado State University for much statistical analysis and advice over many years.


AUGUST FORECAST VERIFICATION


Eric Blake spent from 1998-2001 as a graduate student at Colorado State University. His research efforts went into the development of an Atlantic basin August-only hurricane forecast scheme which was used for our 5 August 2005 forecast. See Blake (2002) or Blake and Gray (2004) for background information. Our August 2005 forecast called for well above-average activity, and this forecast verified remarkably well.


CSU forecast and verification of August-only hurricane activity made in early August

Tropical Cyclone Parameters and August 2005 Adjusted August August 2005
1950-2000 August Average (in parentheses)Statistical Forecast 2005 Forecast Verification
Named Storms (NS) (2.8) 3.2 5 5
Named Storm Days (NSD) (11.8) 12.1 20 21
Hurricanes (H) (1.6) 1.3 3 2
Hurricane Days (HD) (5.7) 6.7 10 7
Intense Hurricanes (IH) (0.6) 0.9 1 1
Intense Hurricane Days (IHD) (1.2) 2.8 3 2.5
Net Tropical Cyclone Activity (NTC) (26.4) 33.7 50 42

1  Introduction

       Our Colorado State University research project has shown that a sizable portion of the year-to-year variability of Atlantic tropical cyclone (TC) activity can be hindcast with skill significantly exceeding climatology. These forecasts are based on a statistical methodology derived from 55 years of past global reanalysis data and a separate study of prior analog years which have had similar global atmosphere and ocean precursor circulation features to this year. Qualitative adjustments are added to accommodate additional processes which may not be explicitly represented by our statistical analyses. We believe that seasonal forecasts must be based on methods showing significant hindcast skill in application to long periods of prior seasonal and monthly data.

2  Predictions of Individual Monthly Atlantic TC Activity

       An aspect of our climate research besides our seasonal forecasts is the development of TC activity predictions for individual months. On average, August, September and October have about 26%, 48%, and 18% or 92% of the total Atlantic basin NTC activity. Initial August-only forecasts have now been made for the last six seasons, September-only forecasts have been made for the last four seasons, and October-only forecasts have been made for the last three seasons.


There are often monthly periods within active and inactive hurricane seasons which do not conform to the overall season. To this end, we have recently developed new schemes to forecast August-only, September-only and October-only Atlantic basin hurricane activity by the beginning of each respective month. These efforts have been recently documented in papers by Blake and Gray (2004) for our August-only forecast and by Klotzbach and Gray (2003) for our September-only forecast - see the references at the end.


Quite skillful August-only, September-only and October-only prediction schemes have been developed based on 51 years (1950-2000) of hindcast testing using a statistically independent jackknife approach. Predictors are derived from prior month, usually June and July NCEP global reanalysis data for all three (August-only, September-only and October-only) individual monthly forecasts and include August's data for the early September update of the September-only and October-only forecasts. Table 1 gives an outline and timetable of the different forecasts and the verifications we issue after the end of each month.


Table 1: Timetable of the issuing of our after-July monthly forecasts (in early August, early September, and early October), the times of their verifications, and the dates of seasonal updates. Note that we make three separate October-only forecasts; two separate September-only forecasts; and one separate August-only forecast. Seasonal updates are issued in early September and early October.


Times of Forecast Based on
and Verification Data Through Forecasts
Early August JulyForecast for Aug. Forecast for Sept. Forecast for Oct. Remainder of Season Fcst.
Early September AugustAugust Verification Forecast for Sept. Forecast for Oct. Remainder of Season Fcst.
Early October SeptemberSept. Verification Forecast for Oct. Remainder of Season Fcst.


Through August, the 2005 hurricane season has had 110 percent of the NTC activity of the average hurricane season. June-July 2005 had the largest values of Net Tropical Cyclone activity for any June-July period on record. August was also very active, experiencing about 150 percent of average August tropical cyclone activity. As of 1 September, twelve named storms, four hurricanes and three major (Cat. 3-4-5) hurricanes have developed. This 2005 activity is to be compared with the average number of named storms based upon the 1950-2000 climatology. Through August, the climatological average number of named storms, hurricanes and major hurricanes is 4.2, 2.4, and 0.7, respectively. Through August of 2005, the Atlantic basin has witnessed 262, 167, and 429 percent of average named storm, hurricane, and major hurricane activity, respectively.


2.1  September Forecast

      Table 2 and Fig. 1 list the nine September-only predictors with their location and sign for higher TC activity. Table 3 shows which of the nine predictors are used for each forecast parameter of NS, NSD, H, etc.


Table 2: Meteorological predictors, their location, and abbreviated name which is used for the September-only forecast. A plus (+) means that positive values of the predictor are associated with increased hurricane activity, and a minus (-) indicates that negative values of the predictor are associated with increased hurricane activity.


Name of Predictor Location Abbreviated Predictor Name
1) April 1000 mb U (-) (12.5-30S, 10-40E) April S Atl 1000 mb U
2) July 200 mb Geo Ht. (+) (32-42N, 100-160E) July Asian 200 mb Geo Ht
3) July-Aug. 1000 mb U (+) (-) (5-15N, 30-50W) -
(22.5-35N, 35-65W) July-Aug Atl 1000 mb U
4) Feb. 1000 mb U (-) (20-30N, 15W-15E) Feb W Africa 1000 mb U
5) April 200 mb U (-) (67.5-85N, 110-180E) April NE Siberia 200 mb U
6) August SLP (-) (0-30S, 120-160E) Aug Indonesia SLP
7) August SLP (-) (20-45S, 60-90E) Aug S Indian Ocean SLP
8) May 200 mb V (+) (0-20S, 15-30E) May C Africa 200 mb V
9) Jan-Feb 200 mb U (-) (15-25N, 120E-160W) Jan-Feb W Pac 200 mb U

Figure4.2.png

Figure 1: Predictors utilized for the September-only forecast which employs meteorological data through August. Numbers of each area are keyed to the predictor description given in Table 2.

Table 3: September-only meteorological predictors used to forecast each TC parameter. A plus (+) means that positive values of the predictor are associated with increased hurricane activity, and a minus (-) indicates that negative values of the predictor are associated with increased hurricane activity.


Abbreviated Predictor Name Equations Used
1) April S Atl 1000 mb U (-) IH
2) July Asian 200 mb Geo Ht. (+) NSD, H, IH, NTC
3) July-Aug. Atl 1000 mb U (+) (-) H, HD, IH, IHD, NTC
4) Feb W Africa 1000 mb U (-) NS, NSD, HD, IHD, NTC
5) April NE Siberia 200 mb U (-) NS, NSD, HD, IH, IHD, NTC
6) Aug Indonesia SLP (-) NS, NSD, HD
7) Aug S Indian Ocean SLP (-) NS, H
8) May C Africa 200 mb V (+) NS, NSD, H, HD, IH, NTC
9) Jan-Feb W Pac 200 mb U (-) IHD


Table 4 lists the value of each September-only predictor and whether its 2005 value indicates above or below average September-only TC activity. Six out of nine predictors indicate an above-average month. We are calling for a very active September, due in part to the greatly enhancing Atlantic SST pattern presently in place.

Table 4: Values of meteorological parameters for the September-only forecast.


Predictor 2005 Observed Values Effect on 2005 Hurricane Season
1) April 1000 mb U (-) -0.1 SD Enhance
2) July 200 mb Geo Ht. (+) +0.5 SD Enhance
3) July-Aug. 1000 mb U (+) +0.1 SD Enhance
4) Feb. 1000 mb U (-) +1.3 SD Suppress
5) April 200 mb U (-) -0.1 SD Enhance
6) August SLP (-) +1.3 SD Suppress
7) August SLP (-) -0.1 SD Enhance
8) May 200 mb V (+) +1.2 SD Enhance
9) Jan-Feb 200 mb U (-) +1.2 SD Suppress


Our early September update of September TC activity keeps our forecast for September the same (see Table 5). We have not seen any conditions which would give us pause in forecasting another very active month. Sea surface temperatures are very warm, and vertical wind shear remains quite favorable for development in the tropical Atlantic and Caribbean. Also, when July and August are active in the deep tropics (as they have been during 2005), September activity tends to also be enhanced.


Table 5: 2005 September-only forecasts based on meteorological data through July (a) - left two columns. This forecast was issued in early August. September-only forecasts based on meteorological data through August (b) - right two columns.


(a) (b)
5 Aug. 2005 5 Aug. 2005 2 Sep. 2005 2 Sep. 2005
September 1950-2000 Sep.-only Sep.-only Sep.-only Sep.-only
Climatology Statistical Adjusted Statistical Adjusted
(in parentheses) Forecast Forecast Forecast Forecast
Named Storms (NS) (3.4) 4.0 5.0 2.7 5.0
Named Storm Days (NSD) (21.7) 25.9 31.0 17.4 31.0
Hurricanes (H) (2.4) 3.5 4.0 3.0 4.0
Hurricane Days (HD) (12.3) 13.0 22.0 9.4 22.0
Intense Hurricanes (IH)(1.3)1.4 2.0 1.7 2.0
Intense Hurricane Days (IHD) (3.0) 1.1 6.0 0.0 6.0
Net Tropical Cyclone Activity (NTC) (48)49 80 54 80

2.2  Independent October-only Statistical Forecast

       Through examination of the NCEP/NCAR reanalysis, we have discovered four predictors that in combination explain about 60 percent of the October cross-validated variance in Net Tropical Cyclone activity (at 1 September) for the hindcast period of 1950-2001. We are currently unable to find combinations of predictors that explain large amounts of variance for the individual tropical cyclone parameters (i.e., named storms, hurricane days, etc.). Therefore, our October forecast consists of predicting NTC and consequently increasing or decreasing October's values for the other parameters accordingly. For example, if October NTC was 150 percent of normal, and a typical October had two named storms, we would forecast three named storms for October.


Table 6 and Fig. 2 list the four October-only predictors with their location and sign for enhanced TC activity.


Table 6: Meteorological predictors, their location, and abbreviated name which is used for the October-only forecast. A plus (+) means that positive values of the predictor are associated with increased hurricane activity, and a minus (-) indicates that negative values of the predictor are associated with increased hurricane activity.


Name of Predictor Location Abbreviated Predictor Name
1) July-August SLP (-) (12.5-27.5N, 15-45W) July-Aug Subtropical Atl SLP
2) July-August 200 mb U (+) (35-47.5S, 160E-155W) July-Aug South Pac 200 mb U
3) Prev. Nov SLP (-) (45-65N, 115-145W) Prev. Nov North Pac SLP
3) August SST (+) (22.5-35N, 120-150E) Aug. North Pac SST

Octoberpredictors.png

Figure 2: Predictors utilized for the October-only forecast which employs meteorological data through August. Numbers of each area are keyed to the predictor description given in Table 6.


Table 7 lists the value of each October-only predictor and whether its 2005 value indicates above or below average October-only TC activity. A majority of the October predictors call for below-average activity.

Table 7: Values of meteorological predictors for the October-only forecast.


Predictor 2005 Observed Values Effect on 2005 Hurricane Season
1) July-August SLP (-) +0.2 SD Suppress
2) July-August 200 mb U (+) -0.3 SD Suppress
3) Prev. November SLP (-) +0.7 SD Suppress
4) August SST (+) +0.8 SD Enhance


Three out of the four October predictors are negative. However, our early August forecast for October indicated above-average activity, and we believe that the current favorable conditions are likely to last for the remainder of the 2005 hurricane season. We are reducing our October forecast slightly, though, due to the fact that three of the four predictors for October are negative for storm activity. During the 2004 hurricane season, activity was at record levels for August and September but died off in October due to a developing El Niño event which increased vertical wind shear. We do not expect an El Niño event to develop this fall, and therefore, we expect an active end to the hurricane season. We continue to call for well above-average October activity with an NTC of about 175 percent of the typical October value (Table 8). In round numbers, we are forecasting 3 named storms, 2 hurricanes, 1 intense hurricane and an NTC of 30 for October.


Table 8: 2005 October-only forecasts based on meteorological data through July (a) - left two columns. This forecast was issued in early August. October-only forecasts based on meteorological data through August (b) - right two columns.


(a) (b)
5 Aug. 2005 5 Aug. 2005 2 Sep. 2005 2 Sep. 2005
September 1950-2000 Oct.-only Oct.-only Oct.-only Oct.-only
Climatology Statistical Adjusted Statistical Adjusted
(in parentheses) Forecast Forecast Forecast Forecast
Named Storms (NS) (1.7) 2.1 3.0 1.5 3.0
Named Storm Days (NSD) (9.0) 11.0 13.0 8.1 13.0
Hurricanes (H) (1.1) 1.3 2.0 1.0 2.0
Hurricane Days (HD) (4.4) 5.4 7.0 4.0 6.0
Intense Hurricanes (IH)(0.3)0.4 1.0 0.3 1.0
Intense Hurricane Days (IHD) (0.8) 1.0 2.0 0.7 1.0
Net Tropical Cyclone Activity (NTC) (18)21 35 16 30


Table 9 displays a summary of this year's hurricane activity through August and our projection for the rest of the season. We expect September and October activity to be above their climatological averages. We assume no activity in November.


Table 9: Summary of hurricane activity through August 2005 and projected hurricane activity for the remainder of the year.



Tropical Cyclone Parameters Observed Updated Updated Updated
and 1950-2000 Full Season Climatology TC Activity Sept. Oct. Full Season
(in parentheses) Through August Forecast Forecast Forecast
Named Storms (NS) (9.6) 12 5 3 20
Named Storm Days (NSD) (49.1) 49 31 13 95
Hurricanes (H) (5.9) 4 4 2 10
Hurricane Days (HD) (24.5) 18 22 6 45
Intense Hurricanes (IH)(2.3)3 2 1 6
Intense Hurricane Days (IHD) (5.0) 8.25 6 1 15
Net Tropical Cyclone Activity (NTC) (100)110 80 30 220



3  U.S. Landfall Probability Forecast for September and October

       We have recently developed a methodology for calculating the probability of hurricane landfall along the entire U.S. coastline for the months of September and October. Based on a 1950-2001 dataset, the probability of various intensity classes of tropical cyclones making landfall in September and October is based on September and October NTC values. For our forecast of a September 2005 NTC of 80, our United States landfall probabilities are given in Table 10. Table 11 displays the landfall probabilities for October. Landfall probabilities for the U.S. are above average for this September and October based on an above-average forecast of Atlantic basin NTC for both September and October.


Table 10: Estimated probability (expressed in percent) of one or more U.S. landfalling tropical storms (TS), category 1-2 hurricanes (HUR) and category 3-4-5 hurricanes (IH) making landfall along the entire U.S. coast for September 2005 based on a September NTC forecast of 80. The long-term mean annual probability of one or more landfalling systems during the last 52 years is given in parentheses for September.


September 2005 Probability
Named Storm (67%) 75%
Hurricane (48%) 54%
Intense Hurricane (27%) 43%


Table 11: Estimated probability (expressed in percent) of one or more U.S. landfalling tropical storms (TS), category 1-2 hurricanes (HUR) and category 3-4-5 hurricanes (IH) making landfall along the entire U.S. coast for October 2005 based on an October NTC forecast of 30. The long-term mean October probability of one or more landfalling systems during the last 52 years is given in parentheses.


October 2005 Probability
Named Storm (29%) 49%
Hurricane (15%) 21%
Intense Hurricane (6%) 15%


4  United States Major Hurricane Landfall Since 1995

       The global climate signals since 1995 have been similar to the global climate signals of the mid-1920s to the mid-1960s when many more major hurricanes struck the US East Coast and Florida. Between 1995-2003, only 3 of 32 major Atlantic basin hurricanes (Cat. 3-4-5) made United States landfall (Opal (1995), Fran (1996), Bret (1999)). Since August of last year, we have had five major hurricanes make landfall (Charley (2004), Ivan (2004), Jeanne (2004), Dennis (2005), and Katrina (2005)). The long-term average is about one in three. Even though the US has experienced five major hurricane strikes since August 2004, in terms of the number of U.S. major hurricane strikes during the last 11 years (8 of 41 versus one of three for the century-long average) we have been, from this perspective, rather fortunate.


5  Difference in 2005 versus 2004 June-July TC Activity

       Although both the 2004 and 2005 seasons will likely have nearly comparable seasonal NTC activity, the June-July period of each season was very different. June-July 2004 had no TC activity while June-July 2005 had the most early season tropical cyclone activity on record (7 named storms, 2 hurricanes, 2 major hurricanes and an NTC of 68).


These June-July activity differences are well explained by the large June-July increases in 2005 over 2004 for several enhancing Atlantic tropical cyclone features including:

  1. Higher Atlantic sea surface temperatures (SST)

  2. Lower Atlantic sea level pressures (SLP)

  3. Weaker low-latitude trade winds

  4. Stronger low-latitude upper-tropospheric easterly winds; the combination of 3 and 4 results in reduced vertical wind shear

  5. Moister lower and middle atmosphere


6  United States Landfalling Hurricane Webpage Application

       Over the past four years, we have been compiling and synthesizing our landfalling hurricane data and have developed a webpage application with extensive landfall probabilities for the Gulf and East Coasts of the United States. In partnership with the GeoGraphics Laboratory at Bridgewater State College, a web application has been created that displays landfall probabilities for eleven regions, 55 subregions and all 205 U.S. coastal and near-coastal counties from Brownsville, Texas to Eastport, Maine. Individual probabilities of sustained winds of tropical storm force (40-75 mph), hurricane force ( 75 mph) and intense or major hurricane force ( 115 mph) are also given. These probabilities are based on the current forecast of NTC activity and on current values of SSTA*. Probabilities of winds in the vicinity of a subregion and county as well as 50-year probabilities for winds of tropical storm force, hurricane force, and intense or major hurricane force are also provided. These probabilities have recently been updated with data from the latter part of the 19th century with the release of the first part of the HURDAT reanalysis (Landsea et al. 2005). Table 12 summarizes the data currently available on the webpage.

Table 12: Data currently available on our CSU landfalling hurricane probability webpage.


Annual Landfall ProbabilityAnnual Vicinity Probability50-Year Probability
NS X X X
H X X X
IH X X X

Landfall_Webpage1.png

Figure 3: View of landfalling hurricane webpage centered on Subregion 1E - the Houston/Galveston metropolitan area.


Figure4.png

Figure 4: Example of data available from the United States landfalling hurricane webpage.


Figures 3 and 4 display example screens of data that is available on this website. The user can select tracks of all intense hurricanes that have made landfall in a given area over the last 100 years. This webpage is currently available at http://www.e-transit.org/hurricane. One can also reach this webpage from a link off the CSU Tropical Meteorology Project homepage: http://hurricane.atmos.colostate.edu.

7  The 1995-2005 Upswing in Atlantic Hurricanes and Global Warming

       Many individuals have queried whether the unprecedented landfall of four destructive hurricanes in a seven-week period during August-September 2004 and the landfall of two more major hurricanes in the early part of the 2005 season is related in any way to human-induced climate changes. There is no evidence that this is the case. If global warming were the cause of the increase in United States hurricane landfalls in 2004 and 2005 and the overall increase in Atlantic basin major hurricane activity of the past eleven years (1995-2005), one would expect to see an increase in tropical cyclone activity in the other storm basins as well (ie., West Pacific, East Pacific, Indian Ocean, etc.). This has not occurred. When tropical cyclones worldwide are summed, there has actually been a slight decrease since 1995. In addition, it has been well-documented that the measured global warming during the 25-year period of 1970-1994 was accompanied by a downturn in Atlantic basin major hurricane activity over what was experienced during the 1930s through the 1960s.


We attribute the heightened Atlantic major hurricane activity between 1995-2005 to be a consequence of the multidecadal fluctuations in the Atlantic Ocean thermohaline circulation (THC) as we have been discussing in our Atlantic basin seasonal hurricane forecasts for several years. Major hurricane activity in the Atlantic has been shown to undergo marked multidecadal fluctuations that are directly related to North Atlantic sea surface temperature anomalies. When the Atlantic Ocean thermohaline circulation is running strong, the central Atlantic equatorial trough (ITCZ) becomes stronger. The stronger the Atlantic equatorial trough becomes, the more favorable are conditions for the development of major hurricanes in the central Atlantic. Since 1995, the THC has been flowing more strongly, and there has been a concomitant increase in major hurricanes in the tropical Atlantic.

8  Forecast Theory and Cautionary Note

      Our forecasts are based on the premise that those global oceanic and atmospheric conditions which precede comparatively active or inactive hurricane seasons in the past provide meaningful information about similar trends in future seasons. It is important that the reader appreciate that these seasonal forecasts are based on statistical schemes which, owing to their intrinsically probabilistic nature, will fail in some years. Moreover, these forecasts do not specifically predict where within the Atlantic basin these storms will strike. The probability of landfall for any one location along the coast is very low and reflects the fact that, in any one season, most US coastal areas will not feel the effects of a hurricane no matter how active the individual season is. However, it must also be emphasized that a low landfall probability does not insure that hurricanes will not come ashore.

9  Forthcoming Update Forecasts of 2005 Hurricane Activity

      We will be issuing a final seasonal update of our 2005 Atlantic basin hurricane activity forecast on Monday 3 October 2005. This 3 October forecast will include a separate forecasts of October-only Atlantic basin tropical cyclone activity. A verification and discussion of all 2005 forecasts will be issued in late November 2005. Our first seasonal hurricane forecast for the 2006 hurricane season will be issued in early December 2005. All these forecasts will be available at our web address given on the front cover: http://hurricane.atmos.colostate.edu/Forecasts .

10  Acknowledgments

       Besides the individuals named on page 2, there have been a number of other meteorologists that have furnished us with data and given valuable assessments of the current state of global atmospheric and oceanic conditions. This includes Arthur Douglas, Richard Larsen, Todd Kimberlain, Ray Zehr and Mark DeMaria. In addition, Barbara Brumit and Amie Hedstrom have provided excellent manuscript, graphical, and data analysis assistance over a number of years. We have profited over the years from many indepth discussions with most of the current and past NHC hurricane forecasters. The first author would further like to acknowledge the encouragement he has received for this type of forecasting research application from Neil Frank, Robert Sheets, Robert Burpee, Jerry Jarrell, former directors of the National Hurricane Center (NHC), and from the current director, Max Mayfield and their forecast staffs. Uma Shama and Larry Harman of Bridgewater State College, MA have provided assistance and technical support in the development of our Landfalling Hurricane Probability Webpage. We also thank Bill Bailey of the Insurance Information Institute for his sage advice and encouragement.


The financial backing for the issuing and verification of these forecasts has in part been supported by the National Science Foundation and by the Research Foundation of Lexington Insurance Company (a member of the American International Group). We also thank the GeoGraphics Laboratory at Bridgewater State College for their assistance in developing the Landfalling Hurricane Probability Webpage.

11  Citations and Additional Reading

12  Verification of Previous Forecasts


Table 13: Summary verification of the authors' six previous years of seasonal forecasts for Atlantic TC activity between 1999-2004. Verification of our earlier year forecasts for the years 1984-1998 are given in our late November seasonal verifications (on this Web location).


Update Update Update
1999 5 Dec 19987 April 4 June6 August Obs.

No. of Hurricanes 9 9 9 9 8
No. of Named Storms 14 14 14 14 12
No. of Hurricane Days 40 40 40 40 43
No. of Named Storm Days 65 65 75 75 77
Hurr. Destruction Potential(HDP) 130 130 130 130 145
Major Hurricanes (Cat. 3-4-5)4 4 4 4 5
Major Hurr. Days 10 10 1010 15
Net Trop. Cyclone (NTC) Activity 160 160 160 160 193

Update Update Update
2000 8 Dec 1999 7 April 7 June4 August Obs.

No. of Hurricanes 7 7 8 7 8
No. of Named Storms 11 11 12 11 14
No. of Hurricane Days 25 25 35 30 32
No. of Named Storm Days 55 55 65 55 66
Hurr. Destruction Potential(HDP) 85 85 100 90 85
Major Hurricanes (Cat. 3-4-5)3 3 4 3 3
Major Hurr. Days 6 6 8 6 5.25
Net Trop. Cyclone (NTC) Activity 125 125 160 130 134

Update Update Update
2001 7 Dec 20006 April 7 June7 August Obs.

No. of Hurricanes 5 6 7 7 9
No. of Named Storms 9 10 12 12 15
No. of Hurricane Days 20 25 30 30 27
No. of Named Storm Days 45 50 60 60 63
Hurr. Destruction Potential(HDP) 65 65 75 75 71
Major Hurricanes (Cat. 3-4-5)2 2 3 3 4
Major Hurr. Days 4 4 5 5 5
Net Trop. Cyclone (NTC) Activity 90 100 120 120 142

Update Update Update Update
2002 7 Dec 20015 April 31 May7 August 2 Sept Obs.

No. of Hurricanes 8 7 6 4 3 4
No. of Named Storms 13 12 11 9 8 12
No. of Hurricane Days 35 30 25 12 10 11
No. of Named Storm Days 70 65 55 35 25 54
Hurr. Destruction Potential(HDP) 90 85 75 35 25 31
Major Hurricanes (Cat. 3-4-5)4 3 2 1 1 2
Major Hurr. Days 7 6 5 2 2 2.5
Net Trop. Cyclone (NTC) Activity 140 125 100 60 45 80

Update Update Update Update Update
2003 6 Dec 2002 4 April 30 May6 August 3 Sept 2 Oct. Obs.

No. of Hurricanes 8 8 8 8 7 8 7
No. of Named Storms 12 12 14 14 14 14 17
No. of Hurricane Days 35 35 35 25 25 35 33
No. of Named Storm Days 65 65 70 60 55 70 75
Hurr. Destruction Potential(HDP) 100 100 100 80 80 125 131
Major Hurricanes (Cat. 3-4-5)3 3 3 3 3 2 3
Major Hurr. Days 8 8 8 5 9 15 17
Net Trop. Cyclone (NTC) Activity 140 140 145 120 130 155 173

Update Update Update Update Update
2004 5 Dec 2003 2 April 28 May 6 August 3 Sept 1 Oct Obs.

No. of Hurricanes 7 8 8 7 8 9 9
No. of Named Storms 13 14 14 13 16 15 14
No. of Hurricane Days 30 35 35 30 40 52 46
No. of Named Storm Days 55 60 60 55 70 96 90
Major Hurricanes (Cat. 3-4-5) 3 3 3 3 5 6 6
Major Hurr. Days 6 8 8 6 15 23 22
Net Trop. Cyclone (NTC) Activity 125 145 145 125 185 240 229


Footnotes:

1Professor of Atmospheric Science

2Research Associate

3Research Associate


File translated from TEX by TTH, version 3.12.
On 1 September 2005, 10:57.