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Roger Smith

2018 North Atlantic tropical storm / hurricane season forecast contest

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What kind of North Atlantic tropical cyclone season do you foresee? 

Our annual contest asks you to predict the total number of storms, and break it down by months. As you know, the "count" is total number of named storms, then total number of those that become hurricanes, and finally total number of hurricanes that become major (cat-3 or stronger). 

Last year the final count was 17/10/6 and our contest winner was Rockchalk83. 

The rules are fairly simple. You need to post a seasonal total by the deadline which I am setting as June 4th as we often seem to be getting entries past the season's June 1st starting point. I will try to expand the field by publicizing the contest in regional forums this year. 

Your seasonal total should include any developments in May, but if there is an outcome (GFS keeps showing a late May hurricane in the eastern Gulf) earlier forecasts that are backed up by monthly predictions will be adjusted if it appears that the May storm is not anticipated. Seasonals that have no complete monthly component will be left unadjusted as it could be assumed that the May storm is included. 

Last year, all entrants gave monthly predictions and almost all left them unedited, but the contest rules allow you to submit these up to 06z of the first of each month, or to revise them by that deadline. Note, there is no requirement for your monthly numbers to add up to your seasonal numbers and you can use decimal points to express uncertainty. Since most of the seasonal forecasts were the sum of the monthly predictions, I assumed that any May activity could be factored in. Some past years, we have had to deal with even earlier storms that happened before the contest announcement (January, April). 

I am going to post my forecast mostly as a guide to how your forecast should appear (not the numbers but the format) ...

Roger Smith ____ 21 16 7 ____ (Jun) 2 1 0 _ (Jul) 1 1 0 __ (Aug) 4 3 2 __ (Sep) 7 5 3 __ (Oct) 5 4 2 __ (Nov-Dec) 1 1 0

(this assumes a 1 1 0 May, would be adjusted to 20 15 7 if 0 0 0 or 21 15 7 if 1 0 0)

Scoring for the contest is as follows:

50% of the score is based on the seasonal. You start with 50 points and in each category, you lose half of (1 point per error plus that number squared). Example, you predict 16 storms, the actual is 19, your error is (3 + 3 squared)/2 = 12/2 = 6. If you had similar errors for hurricanes and majors, your total score would then be 32/50. 

The other 50% of the score is based on your monthly forecasts starting with June and ending with Nov-Dec. These are worth 4, 6, 12, 16, 10 and 2 points in order from June to Nov-Dec. Then the errors reduce your possible score in the same way as the seasonal formula, except that June, July and Nov-Dec go with half the reductions (in other words, you lose points at half the rate of the other more active months). 

In the past few years, highest scores in the contest have been close to 90 and seasonal scores of 48 to 50 have been achieved. A good monthly set will earn 41-43 points. 

Good luck if you enter. The deadline will be made more precise around June 1st and all entrants can edit up to the eventual deadline without notice, you can assume that I won't be copying down or storing any forecasts until a firm deadline is posted in the thread and up to that firm deadline, so no need to post new numbers, just edit the old ones. Once a table of entries appears, your numbers are set for the seasonal and June portions but you have the option of posting revised monthly numbers at any point during the contest before monthly deadlines. Late monthly revisions will be penalized at a rate of 10% per day but will not be valid after any named storm is declared in the month. 

As you see, I am expecting a very active season. There seems to be no particular reason why the outcome from 2017 would change very much this year, hopefully the majors will stay out to sea more often and avoid the sorts of landfalls that caused so much devastation in 2017. 


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