FORECAST OF ATLANTIC HURRICANE ACTIVITY FOR OCTOBER 2005 AND SEASONAL
UPDATE THROUGH SEPTEMBER
The 2005 Atlantic basin hurricane season has already been one of the most active and is already the most destructive season on record. We project that October will continue the trend of above-average activity that we have witnessed in the preceding four months of the hurricane season.
(as of 3 October 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 at http://hurricane.atmos.colostate.edu/Forecasts
Brad Bohlander and Emily Wilmsen, Colorado State University Media
Representatives, (970-491-6432) are available to answer various questions about
this forecast
Department of Atmospheric Science
Email: barb@atmos.colostate.edu
________________________________
1Professor of Atmospheric Science
2Research Associate
3Research Associate
ABSTRACT
Information
obtained through 30 September 2005 shows that we have already experienced a
very active hurricane season in the Atlantic basin. The season has already accumulated 183 NTC4
units which makes it the seventh most active full season since 1950. In an average season, about 80 NTC units
occur before the end of September.
Our
October-only forecast calls for three named storms, two hurricanes, one major
hurricane and NTC activity of 30 which is well above the mean October-only
average value of 18. We expect that by
the time the 2005 hurricane season is over, we will witness seasonal tropical
cyclone activity at near-record levels.
A seasonal verification of all 2005 activity will be issued on Friday,
November 19.
2005
|
Full Season Tropical
Cyclone Parameters and their 1950-2000 Climatology (in parentheses) |
Full Season Adjusted 5 Aug.
2005 Forecast |
Observed Activity Through
September |
Updated October-only
Forecast |
Full Season Adjusted 3
Oct. 2005 Forecast |
|
Named Storms (NS) (9.6) |
20 |
17 |
3 |
20 |
|
Named Storm Days (NSD)
(49.1) |
95 |
85 |
13 |
100 |
|
Hurricanes (H) (5.9) |
10 |
9 |
2 |
11 |
|
Hurricane Days (HD) (24.5) |
55 |
35 |
6 |
40 |
|
Intense Hurricanes (IH)
(2.3) |
6 |
5 |
1 |
6 |
|
Intense Hurricane Days
(IHD) (5.0) |
18 |
11.75 |
1 |
13 |
|
Net Tropical Cyclone
Activity (NTC) (100%) |
235 |
183 |
30 |
215 |
Acknowledgment
We
are grateful to the National Science Foundation (NSF) and Lexington Insurance
Company (a member of the American International Group (AIG)) 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
________________________________
4NTC is a combined measure of the yearly mean of six
indices (NS, NSD, H, HD, IH, IHD) of hurricane activity as a percent deviation
from the 1950-2000 year average.
VERIFICATION OF INDIVIDUAL AUGUST AND
SEPTEMBER MONTHLY FORECASTS
Our forecast and verification of
August-only hurricane activity made in early August – a forecast that verified
remarkably well
|
Tropical Cyclone
Parameters and 1950-2000 August Average (in parentheses) |
August 2005 Statistical
Forecast |
Adjusted August 2005
Forecast |
August 2005 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%) |
33.7 |
50 |
42 |
Our forecast and verification of
September-only hurricane activity made in early September – another successful
forecast
|
Tropical Cyclone
Parameters and 1950-2000 September Average (in parentheses) |
September 2005 Statistical
Forecast |
Adjusted September 2005
Forecast |
September 2005
Verification |
|
Named Storms (NS) (3.4) |
2.7 |
5 |
5 |
|
Named Storm Days (NSD) (21.7) |
17.4 |
31 |
36 |
|
Hurricanes (H) (2.4) |
3.0 |
4 |
5 |
|
Hurricane Days (HD) (12.3) |
9.4 |
22 |
18 |
|
Intense Hurricanes (IH) (1.3) |
1.7 |
2 |
2 |
|
Intense Hurricane Days
(IHD) (3.0) |
0.0 |
6 |
3.5 |
|
Net Tropical Cyclone
Activity (NTC) (48%) |
54 |
80 |
73 |
1
2005
As of the end of September, 2005 has
had seventeen named storms, nine hurricanes and five major hurricanes. Three major hurricanes have made
Table 1: Observed 2005 tropical cyclone activity through September.
|
Highest Category |
Name |
Dates |
Peak Sustained Winds
(kts)/lowest SLP (mb) |
NSD |
HD |
IHD |
NTC |
|
TS |
Arlene |
June 9-11 |
60 kt/989 mb |
2.50 |
|
|
2.6 |
|
TS |
Bret |
June 29-29 |
35 kt/1002 mb |
0.50 |
|
|
1.9 |
|
TS |
Cindy |
July 5-6 |
60 kt/992 mb |
1.25 |
|
|
2.2 |
|
IH-4 |
Dennis |
July 5-11 |
130 kt/930 mb |
5.75 |
4.00 |
2.00 |
23.1 |
|
IH-4 |
Emily |
July 12-21 |
135 kt/929 mb |
9.25 |
6.75 |
3.75 |
32.0 |
|
TS |
|
July 22-29 |
60 kt/997 mb |
8.00 |
|
|
4.5 |
|
TS |
Gert |
July 24-25 |
40 kt/1005 mb |
1.00 |
|
|
2.1 |
|
TS |
|
Aug. 3-8 |
55 kt/994 mb |
5.50 |
|
|
3.6 |
|
H-2 |
Irene |
Aug. 7-8, Aug. 11-18 |
85 kt/975 mb |
8.75 |
2.75 |
|
9.4 |
|
TS |
Jose |
Aug. 22-23 |
45 kt/1001 mb |
0.50 |
|
|
1.9 |
|
IH-5 |
Katrina |