Still Predicting an Active Season

Apart from Tropical Storm Alberto, the 2006 North Atlantic hurricane season has been pretty slow so far. That's not unexpected; June is never exactly a rockin' month for hurricanes, although last year, July was a rockin' month. So far it's not clear what to expect; I find the best source of day-to-day information on what's happening in the tropics is Jeff Masters' WunderBlog, which I encourage you to check out.

Meanwhile, despite the season's relatively slow start, one of the leading forecasting groups, Professors Mark Saunders and Adam Lea's Tropical Storm Risk, continues to predict an active upcoming season, although again, not as active as 2005. Tropical Storm Risk has just released another forecast, and it's actually up slightly from what they put out last month. For the Atlantic, thanks to weaker trade winds and (as always) high sea surface temperatures, they're expecting 14.1 tropical cyclones, 7.7 of which become hurricanes, 3.4 of which become intense hurricanes. You can read the full forecast here (PDF).

Finally, Japan is awaiting a strike from Typhoon Ewiniar right now; currently it has 105 knot or 121 mph winds, though it's expected to weaken before landfall as it curves northward over cooler waters. Click here for an impressive satellite image. The Joint Typhoon Warning Center has more on the storm. I will continue to track this coming hurricane season, although thus far, there really hasn't been that much to tell...

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Chris, the historical average number of tropical storms in June is 0.5 . Twice that number is not a slow start by any reasonable definition. It's just not the wild madness of 2005.

llewelly,

If the statistical probability for an event is 0.5 that means that you can expect the event to occur five times in ten chances. That means on average there is a tropical storm every other June. There is no such thing as half a tropical storm.

That means that June reflected a very typical month in historical terms. Nothing out of the ordinary.

(*Warning wry remarks intended as irony ahead. The humor impaired may wish to look away.*)

Cheer up with any luck a really nasty storm will devastate a whole region of the country.

By Lance Harting (not verified) on 06 Jul 2006 #permalink

If the statistical probability for an event is 0.5 that means that you can expect the event to occur five times in ten chances.

So - you understand what I meant - but then:

There is no such thing as half a tropical storm.

this weird notion of half a tropical storm beams in from never-never land. How did you read that into what I said?

If I fumbled some statistical terminology, I apologize, and would you please explain how? I never intended to imply the existence of half tropical storms.

(subtropical storms, (sub)tropical depressions, and other borderline cases do exist, but none are counted as half tropical storms for any commonly used statistic I know of.)

llewelly,

You said "Twice that number is hardly a slow start." This implies that so far there have been twice as many tropical storms as might be expected. As if one might expect 0.5 (or one half) tropical storms to occur. This clearly misinterprets the meaning of a probability of 0.5.

By Lance Harting (not verified) on 08 Jul 2006 #permalink

You said "Twice that number is hardly a slow start."

'that number' was intended to refer to the historical average. The historical average is composed of 0s, 1s, and 2s (1936 had 3 June storms, but I think I got my number from a 1950 - 2005 average. ) I assumed the reader would know this (maybe a bad assumption?)
'hardly a slow start' is intended imply that 1 June TS is not a slow start when compared to historical values - not necessarily what is expected. It assumed there is some relationship between historical values and what is expected, but I don't think it's a simple one.

This implies that so far there have been twice as many tropical storms as might be expected. As if one might expect 0.5 (or one half) tropical storms to occur.

I avoided the word 'expected' because it seems to open several cans of worms. So here it seems you're nitpicking the use of a word I didn't use.

I'm sorry I was unclear, Lance, but I still don't understand how. All I can do is laugh. Nobody expected half a tropical storm, but he we are arguing about them anyway. Usenet lives on, I guess.

No problem llewelly, I didn't meant to pick nits. I was just clarifying the meaning of a 0.5 probability.

By Lance Harting (not verified) on 08 Jul 2006 #permalink

An average number is not a probability. An average of .5 storms in June in 56 years does not mean that there is a 50% chance of getting 1 storm in June. It simply means that in 56 years there were 23 storms. The probability of 1 storm in June is somewhat less than 50%, assuming that some years in the record have 2 storms.

This year the heat content is moving into the north Atlantic and the Carribean is cooler than last year. Expect fewer storms than last year but more than average. The Carribean should have less intense storms. However, the north Atlantic is likely to get very active in September and October and the whole Atlantic seabord needs to be prepared.

_g