FORECAST OF ATLANTIC HURRICANE ACTIVITY FOR SEPTEMBER AND OCTOBER 2006 AND SEASONAL UPDATE THROUGH AUGUST

 

Following below-average activity in August, we are significantly reducing our seasonal forecast. We expect slightly above-average activity in September and that October will likely have below-average activity.  We now predict that total seasonal activity will be slightly below the long-term average.

 

(as of 1 September 2006)

 

 

 

By Philip J. Klotzbach[1] and William M. Gray[2]

 

with special assistance from William Thorson[3]

 

 

 

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


Emily Wilmsen, 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: amie@atmos.colostate.edu

 

ATLANTIC BASIN SEASONAL HURRICANE FORECAST FOR 2006

 

Forecast Parameter and 1950-2000

Climatology (in parentheses)

Full Season Adjusted

 3 August 2006 Fcst.

Observed Activity Through August

Updated Sept.-only Fcst.

Updated Oct.-only Fcst.

Forecast Activity After 1 Sept.

Full Season Adjusted 1 Sep. 2006 Forecast1

Named Storms (NS) (9.6)

15

5

5

2

8

13

Named Storm Days (NSD) (49.1)

75

17.50

20

10

32

50

Hurricanes (H) (5.9)

7

1

3

1

4

5

Hurricane Days (HD) (24.5)

35

0.25

10

3

13

13

Intense Hurricanes (IH) (2.3)

3

0

2

0

2

2

Intense Hurricane Days (IHD) (5.0)

8

0

4

0

4

4

Net Tropical Cyclone Activity (NTC) (100%)

140

18

59

12

73

90

 

 

1 We assume one weak named storm in November that accrues two named storm days.

 

 


Notice of Author Changes

 

By William Gray


The order of the authorship of these forecasts has been reversed from Gray and Klotzbach to Klotzbach and Gray.  After 22 years (since 1984) of making these forecasts, it is appropriate that I step back and have Phil Klotzbach assume the primary responsibility for our project’s seasonal, monthly and landfall probability forecasts.  Phil has been a member of my research project for the last five years and has been second author on these forecasts for the last four years.  I have greatly profited and enjoyed our close personal and working relationships.

 

Phil is now devoting more time to the improvement of these forecasts than I am.  I am now giving more of my efforts to the global warming issue and in synthesizing my projects’ many years of hurricane and typhoon studies.

 

Phil Klotzbach is an outstanding young scientist with a superb academic record.  I have been amazed at how far he has come in his knowledge of hurricane prediction since joining my project five years ago.  I foresee an outstanding future for him in the hurricane field.  I expect he will make many new forecast innovations and skill improvements in the coming years.  I plan to continue to be closely involved in the issuing of these forecasts for the next few years. 



ABSTRACT

 

Information obtained through 31 August 2006 shows that we have so far experienced only 18 percent of the average full season Net Tropical Cyclone (NTC) activity.  We significantly over-estimated August 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 5 named storms, 3 hurricanes, 2 major hurricanes and NTC activity of 59 which is slightly above the September-only average value of 48. Our October-only forecast calls for 2 named storms, 1 hurricane, 0 major hurricanes and NTC activity of 12 which is below the October-only average value of 18.

We now anticipate that the 2006 Atlantic basin tropical cyclone (TC) season will be considerably less active than the seasonal activity we anticipated in our earlier forecasts and in our updated 3 August forecast. We now expect that the 2006 hurricane season will have slightly less hurricane activity than the long-term average.  This is due to an unexpected increase in tropical Atlantic mid-level dryness (with large amounts of African dust) and a continued trend towards El Niño-like conditions in the eastern and central Pacific.   


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 3 August 2006 forecast. See Blake (2002) or Blake and Gray (2004) for background information. Our August 2006 forecast called for well above-average activity, but this forecast did not verify.  Below-average activity occurred during the month.  A more in-depth analysis of why we think August 2006 was an inactive month follows in our discussion (Section 4).

 

 

 

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

 

Tropical Cyclone Parameters and 1950-2000 August Average (in parentheses)

August 2006

Statistical Forecast

Adjusted August 2006 Forecast

August 2006 Verification

Named Storms (NS) (2.8)

3.3

4

3

Named Storm Days (NSD) (11.8)

21.1

22

12

Hurricanes (H) (1.6)

2.9

3

1

Hurricane Days (HD) (5.7)

8.1

11

0.25

Intense Hurricanes (IH) (0.6)

0.7

1

0

Intense Hurricane Days (IHD) (1.2)

2.0

3

0

Net Tropical Cyclone Activity (NTC) (26.4)

53.6

50

12

 

 

Our August 2006 forecast was a bust and not typical of our previous six August-only forecasts for 2000-2005 or our hindcasts of August-only activity as contained in our original developmental datasets over the period 1949-1999.  Our developmental data sets showed considerable skill.  Table A shows the skill of our prior six August-only forecasts for Net Tropical Cyclone (NTC) activity over the 2000-2005 period.  Note that we have correctly predicted above- or below-average in five out of the prior six years. 

 

Table A: Predicted, observed, August-only 2006 forecast (bottom line) and previous five-year mean and climatological NTC for our six August-only forecasts of 2000-2005.   Evaluation of skill with respect to average error and mean square error are also shown. 

 

 

Year        

Observed NTC

Predicted NTC

Previous Five-Year Mean NTC

Climatological NTC

2000

42

33

48

26

2001

9

22

42

26

2002

7

18

31

26

2003

26

22

33

26

2004

89

35

28

26

2005

41

50

35

26

 

 

 

 

 

Average Error (2000-2005)

 

16.7

23.0

21.7

Mean Square Error (MSE) (2000-2005)

 

569

923

851

Skill of Prediction (relative to MSE)

 

 

0.38

0.33

2006

12

50

34

26

 



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. 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

A new aspect of our climate research is the development of TC activity predictions for individual months. There are often monthly periods within active and inactive Atlantic basin hurricane seasons which do not conform to the overall season. For example, 1961 was an active hurricane season (NTC of 222), but there was no TC activity during August; 1995 had 19 named storms, but only one named storm developed during a 30-day period during the peak of the hurricane season between 29 August and 27 September. By contrast, the inactive season of 1941 had only six named storms (average 9.3), but four of them developed during September. During the inactive 1968 hurricane season, three of the eight named storms formed in June (June average is 0.5).

We have conducted new research to see how well various sub-season or individual monthly trends of TC activity can be forecast. This effort has recently been documented in papers by Blake and Gray (2004) for August and Klotzbach and Gray (2003) for September. These reports show that it is possible to develop skillful prediction schemes for August-only and September-only Atlantic basin tropical cyclone activity. We have also developed a separate October forecast scheme. On average, August, September, and October have about 26%, 48%, and 17% or 91% of the Atlantic basin's NTC activity. Initial August-only forecasts have now been made by Blake for the last seven years (2000-2006), and the verification of these forecasts is promising, despite this year’s significant over-forecast. The verification of the September-only and October-only forecasts also appears to show skill.

2.1 Seasonal Update Through August 2006

Through August, the 2006 hurricane season has had 18 percent of the NTC activity of the average hurricane season. June-July 2006 had approximately average activity while August has had below-average activity, experiencing only one-half of average August tropical cyclone activity. As of 1 September, 5 named storms, 1 hurricane and no major (Cat. 3-4-5) hurricanes have developed.  Through August, the climatological (1950-2000) average number of named storms, hurricanes and major hurricanes is 4.2, 2.4, and 0.7, respectively. Through August of 2006, the Atlantic basin has witnessed 120, 42, and 0 percent of average named storm, hurricane, and major hurricane activity, respectively.

 

2.2 September Forecast

      Figure 1 and Table 1 list the predictors used in the September-only hindcast (Klotzbach and Gray 2003) for each of the seven different forecast parameters. The table also shows hindcast skill for the 51-year period 1950-2000, as well as the independent jackknife hindcast skill over this period. Table 2 gives the predictor values for September 2006. Table 3 gives our independent statistical prediction for September 2006.  Predictor values for September 2006 are mixed, so our final forecast is calling for slightly above-average activity for the month.

 

Figure 1:  Predictors selected for the end of August forecast of September tropical cyclone activity.  The numbers in each area are keyed to the description given in Table 1.

 

Table 1: 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 2: September 2006 predictors.  The sign of the predictor associated with increased tropical cyclone activity is in parentheses.

 

 

 

Predictors

2006 Observed Values

 

Effect on 2006 Hurricane Season

1) April 1000 mb U (-)

-0.6 SD

Enhance

2) July 200 mb Geo Ht. (+)

+1.3 SD

Enhance

3) July-Aug 1000 mb U (+)

0.0 SD

Neutral

4) Feb 1000 mb U (-)

+0.8 SD

Suppress

5) April 200 mb U (-)

-1.2 SD

Enhance

6) August SLP (-)

+1.1 SD

Suppress

7) August SLP (-)

-1.7 SD

Enhance

8) Central Africa May 200 mb V (+)

-1.4 SD

Suppress

9) West Pacific Jan-Feb 200 mb U (-)

+0.4 SD

Suppress

 

Our early September forecast of this coming’s September TC activity keeps our forecast for September the same (see Table 3). 

 

Table 3: Independent September-only prediction of 2006 hurricane activity based on Klotzbach and Gray (2003).  September climatology is shown in parentheses. 

 

September 1950-2000 Climatology (in parentheses)

3 Aug. 2006 September-only Statistical Forecast

3 Aug. 2006

September-only

 Adjusted Forecast

1 Sep. 2006 September-only Statistical Forecast

1 Sep. 2006

September-only

 Adjusted Forecast

NS (3.4)

4.1

5

3.4

5

NSD (21.7)

20.8

25

17.2

20

H (2.4)

2.2

3

3.2

3

HD (12.3)

7.2

12

5.5

10

IH (1.3)

1.8

2

1.7

2

IHD (3.0)

1.5

4

2.5

4

NTC (48.0)

48.3

60

45.4

59

 

2.3   October 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 4 and Fig. 2 list the four October-only predictors with their location and sign for enhanced TC activity.

 

 

 

Figure 2:  Location of 1 September predictors for October tropical cyclone activity.

 

Table 4: Meteorological predictors, their location, and abbreviated name which are 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 (-)

(12.5-27.5°N, 15-45°W)

July-Aug Subtropical Atl SLP

2) July-August 200 mb U (+)

(35-47.5°S, 160°E-155°W)

July-Aug South Pac 200 mb U

3) Prev. Nov SLP (-)

(45-65°N, 115-145°W)

Prev. Nov North Pac SLP

4) August SST (+)

(22.5-35°N, 120-150°E)

Aug. North Pac SST

 

Table 5 lists the value of each October-only predictor and whether its 2006 value indicates above- or below-average October-only TC activity.  A majority of the October predictors are calling for above-average activity.

 

Table 5: Values of meteorological predictors for the October-only forecast.

 

Name of Predictor

2006 Observed Value

Effect on 2006 Hurricane Season

1) July-August SLP (-)

-0.3 SD

Enhance

2) July-August 200 mb U (+)

+0.4 SD

Enhance

3) Prev. Nov SLP (-)

0.0 SD

Neutral

4) August SST (+)

+1.2 SD

Enhance

 

 

Three out of the four October predictors are positive for storm activity. Our early August forecast for October indicated below-average activity.  The reason we are forecasting less activity when compared with our statistical scheme is that it appears that an El Niño event may be developing in the equatorial Pacific, and in general, when this occurs, Atlantic basin hurricane seasons come to an early end due to increased vertical wind shear.  We have decreased our October-only forecast slightly from our early August prediction due to the continual westerly wind bursts that have been observed along the equator during August.  The presence of low-level westerlies near the International Date Line drives Kelvin waves eastward which causes anomalous warming in the eastern and central Pacific.  We are calling for below-average October activity with an NTC of 12 (compared with the 1950-2000 average of 18) predicted for the month (Table 6). In round numbers, we are forecasting 2 named storms, 1 hurricane, no intense hurricanes and an NTC of 12 for October.

 

Table 6: Independent October-only prediction of 2006 hurricane activity.  October climatology is shown in parentheses. 

 

October 1950-2000 Climatology (in parentheses)

3 Aug. 2006 October-only Statistical Forecast

3 Aug. 2006

October-only

 Adjusted Forecast

1 Sep. 2006

October-only Statistical Forecast

1 Sep. 2006

October-only

 Adjusted Forecast

NS (1.7)

1.4

2

2.6

2

NSD (9.0)

7.3

11

13.5

10

H (1.1)

0.9

1

1.7

1

HD (4.4)

3.6

4

6.6

3

IH (0.3)

0.2

0

0.5

0

IHD (0.8)

0.6

0

1.2

0

NTC (18)

14.6

15

27.0

12

 

2.4   Seasonal and Monthly Prediction Summary

      Table 7 displays a summary of this year’s hurricane activity through August and our projection for the rest of the season.  We expect activity in September to be slightly above average and activity in October to be below average.  We assume 1 named storm and 2 named storm days in November.

Table 7: Summary of hurricane activity through August 2006 and projected hurricane activity for the remainder of the year

 

Tropical Cyclone Parameters and 1950-2000 Full Season Climatology (in parentheses)

Observed TC Activity through August

Updated September Forecast

Updated

 October

 Forecast

Updated

 Full Season

 Forecast1

Named Storms (NS) (9.6)

5

5

2

13

Named Storm Days (NSD) (49.1)

17.50

20

10

50

Hurricanes (H) (5.9)

1

3

1

5

Hurricane Days (HD) (24.5)

0.25

10

3

13

Intense Hurricanes (IH) (2.3)

0

2

0

2

Intense Hurricane Days (IHD) (5.0)

0

4

0

4

Net Tropical Cyclone Activity (NTC) (100)

18

59

12

90

 

1 We assume one weak named storm in November that accrues two named storm days.

 

 

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. From our 1950-2001 datasets, 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 2006 NTC of 59, our United States landfall probabilities are given in Table 8.  Table 9 displays the landfall probabilities for October. Landfall probabilities for the U.S. are above average for September and near average for October based on an above-average forecast of Atlantic basin NTC for September and an average forecast of Atlantic basin NTC for October.

 

Table 8: 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 2006 based on a September NTC forecast of 59. The long-term mean annual probability of one or more landfalling systems during the last 52 years is given in parentheses for September.

 

Forecast Parameter

September 2006 Probability

Named Storm (67%)

74%

Hurricane (48%)

59%

Intense Hurricane (27%)

35%

 

 

Table 9: 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 2006 based on an October NTC forecast of 12. The long-term mean annual probability of one or more landfalling systems during the last 52 years is given in parentheses for October.

 

Forecast Parameter

October 2006 Probability

Named Storm (29%)

22%

Hurricane (15%)

14%

Intense Hurricane (6%)

4%

 

 

4        Discussion

 

4.1       June-July Discussion

 

June-July 2006 had about average activity with two named storms forming in June and July (Alberto and Beryl).  The long-period average from 1950-2000 is approximately 1.5 named storm formations and 0.6 hurricane formations during the two-month period.  Unlike 2005 when we witnessed two major hurricanes (Dennis and Emily) develop and intensify in the tropical Atlantic and Caribbean, we did not see any activity in the deep tropics during June and July 2006.

 

4.2       Discussion of August 2006 Over-Forecast

 

August 2006 had about average named storm activity, but the amount of hurricane and intense hurricane activity was well below average.  Only one hurricane formed during August (Ernesto), and it lasted less than one day due to interaction with land.  On average, about six hurricane days occur during August.  We think that several features likely contributed to an inactive month.

There was considerable subsidence, dry air and dust across the tropical Atlantic during the month of August.  Subsidence inhibits the development and maintenance of strong thunderstorms which are necessary for the intensification of easterly waves into tropical cyclones.  Two of the three storms that formed during August (Chris and Debby) never reached hurricane strength due partially to very dry air being ingested into their respective circulations.  Figure 3 displays a measure of brightness temperature across the tropical Atlantic.  Brightness temperatures can be considered a measure of mid-level moisture, with colder temperatures indicating more moisture.  Note that brightness temperatures were well above average (i.e. less moisture) throughout most of the month of August. 

 

Figure 3: Water vapor brightness temperature across the tropical Atlantic from January-August.  Note that brightness temperatures have been warmer than average for most of the hurricane season.  Brightness temperatures are a proxy for mid-level moisture, with cooler temperatures indicating more moisture.  Figure courtesy of the Cooperative Institute for Research in the Atmosphere (CIRA). 

 

Vertical wind shear has also inhibited development of tropical cyclones during the month of August.  Shear has been slightly above-average this month, and it certainly played a major factor along with the aforementioned dry air in weakening Chris and Debby. 

In the case of Ernesto, interaction with land decimated the cyclone.  If Ernesto had tracked further westward into the Gulf of Mexico, it is quite likely that it could have become a major hurricane, and NTC for the month of August would have been at least twice as large as the observed value.

 

4.3       Causes of August 2006 Over-Forecast

 

We view our overestimate of the 2006 hurricane season as a result of our inability to predict the substantial amounts of tropical Atlantic mid-level dryness and the extensive amount of African dust that enveloped this area in August. Rainfall in the African Sahel has also been lower than expected.

Another factor leading to a less active hurricane season is the continued development of El Niño-like conditions in the eastern Pacific.  This has resulted in a modest suppression of 200 mb upper tropospheric easterly wind anomalies in the tropical Atlantic, thereby increasing vertical wind shear in the western Atlantic.  Also, there has likely been an increase in subsidence over the tropical Atlantic due to an eastward shift of the Walker Circulation as waters have continued to warm in the central and eastern Pacific.

The increase of this year’s August hurricane activity in the eastern Pacific is another indication of suppressed Atlantic conditions.  These two tropical cyclone basins have tended to be negatively correlated in recent years.  When eastern Pacific activity is enhanced, as it has been this August, Atlantic activity is usually suppressed. 

 

 

5        Is Global Warming Responsible for the Large Upswing in 2004-2005 US Hurricane Landfalls?

 

5.1       Background

 

The U.S. landfall of major hurricanes Dennis, Katrina, Rita and Wilma in 2005 and the four Florida landfalling hurricanes of 2004 (Charley, Frances, Ivan and Jeanne) has raised questions about the possible role that global warming may be playing in these last two unusually destructive seasons.

 

The global warming arguments have been given much attention by many media references to recent papers claiming to show such a linkage.   Despite the global warming of the sea surface of about 0.4°C that has taken place over the last two decades, global numbers of hurricanes and their intensity have not shown increases over the past twenty years (Klotzbach 2006).  In addition, we have no valid physical theory as to why small changes of global average sea surface temperature (SST) should bring about increases in Atlantic basin hurricane activity.  In the past century, Atlantic basin hurricane activity has been above-average both when global SST has been increasing (from the middle 1920s through the middle 1940s) and when global SST has been decreasing (from the middle 1940s through the middle 1960s). 

 

The Atlantic has seen a very large increase in major hurricanes during the last 11-year period of 1995-2005 (average 4.0 per year) in comparison to the prior 25-year period of 1970-1994 (average 1.5 per year).  This large increase in Atlantic major hurricanes is primarily a result of a multi-decadal increase in strength in the Atlantic Ocean thermohaline circulation (THC) which is not directly related to global temperature increase.   Changes in ocean salinity are believed to be the driving mechanism.  These multi-decadal changes have also been termed the Atlantic Multi-Decadal Oscillation (AMO).   It should also be noted that during this same time period, activity in the Northeast Pacific basin has decreased considerably.  When activity in these two basins (the North Atlantic and the Northeast Pacific) is summed together, there has been virtually no trend in major hurricanes. 

 

There have been similar past periods (1940s-1950s) when the Atlantic was just as active as in recent years.  For instance, when we compare Atlantic basin hurricane numbers of the last 15 years with an earlier 15-year period (1950-1964), we see little difference in hurricane frequency or intensity even though global surface temperatures were cooler and there was a general global cooling during 1950-1964 as compared with global warming during 1990-2004. 

 

5.2       Discussion

 

There is no physical basis for assuming that global hurricane intensity or frequency is necessarily related to global mean surface temperature changes of less than ± 0.5oC.  As the ocean surface warms, global upper air temperatures warm as well to maintain conditionally unstable lapse-rates and global rainfall rates at their climatological values.  Seasonal and monthly variations of sea surface temperature (SST) within individual storm basins show only very low correlations with monthly, seasonal, and yearly variations of hurricane activity (Shapiro and Goldenberg 1998, Klotzbach 2006).  Other factors such as tropospheric vertical wind shear, surface pressure, low level vorticity, mid-level moisture, etc. play more dominant roles in explaining hurricane variability than do surface temperatures.  Although there has been a general global warming over the last 30 years and particularly over the last 10 years, the SST increases in the individual tropical cyclone basins have been smaller than the overall global warming (about half) and, according to the observations, have not brought about any significant increases in global major tropical cyclones except for the Atlantic which, as has been discussed, has multi-decadal oscillations driven primarily by changes in Atlantic salinity.    No credible observational evidence is currently available that directly associates global surface temperature change with changes in global or Atlantic hurricane frequency and intensity. 

 

6        Forecast Theory and Cautionary Note

 

Our forecasts are based on the premise that those global oceanic and atmospheric conditions which preceded 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 U.S. 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.  Regardless of how active the 2006 hurricane season is, a finite probability always exists that one or more hurricanes may strike along the U.S. coastline or in the Caribbean and do much damage. 

 

 

7        Forthcoming Updated Forecasts of 2006 Hurricane Activity

 

We will be issuing a seasonal updates of our 2006 Atlantic basin hurricane forecasts on Tuesday 3 October 2006.  The 3 October forecast will include a separate forecast of October-only Atlantic basin tropical cyclone activity.  A verification and discussion of all 2006 forecasts will be issued on Friday 17 November 2006.  Table 10 displays our forecast schedule for the remainder of the 2006 hurricane season.  Our first seasonal hurricane forecast for the 2007 hurricane season will be issued in early December 2006.  All of these forecasts will be made available on the web at: http://hurricane.atmos.colostate.edu/Forecasts.

 

Table 10:  Timetable of upcoming forecasts and updates for the 2006 hurricane season.

 

 

Forecast Date

Based on Data Through

 

Upcoming Forecasts and Updates

3 October 2006

September 2006

September Verification

Updated October Forecast

Updated

 Seasonal

 Forecast

17 November 2006

Verification of all Forecasts

 

 

 

 


[1] Research Associate

[2] Professor Emeritus of Atmospheric Science

[3] Research Associate