Klotzbach and Gray Scale Back the Forecast

One of the best known seasonal hurricane forecasts comes out of Colorado State University courtesy of William Gray (although Gray's student Phil Klotzbach is now lead author of the forecast). Another one comes out of the University College-London Benfield Hazard Research Center courtesy of Mark Saunders and Adam Lea. Both groups update their forecasts monthly; the August Klotzbach-Gray forecast is now out and the August Saunders-Lea forecast will be out tomorrow (I think). So let's see what the first group says...

Gray and Klotzbach are no longer calling for 17 tropical cyclones in the North Atlantic; now they're only predicting 15, or 13 after August 1, one of which (Chris) has already formed. So, if they're right, we will see 12 more total storms this season, of which 7 will be hurricanes and 3 will be major hurricanes (Cat 3, 4, or 5). These last two numbers also indicate a scaling back; originally Klotzbach and Gray were predicting 9 hurricanes and 5 majors.

Why are they scaling back? Let's let them explain it:

1) An increase in sea level pressure values in the tropical Atlantic. Higher sea level pressure values indicate increased stability in the tropical Atlantic which inhibits tropical cyclogenesis.

2) An increase in strength of the trade winds in the tropical Atlantic. Stronger trade winds drive increased evaporation and upwelling which cools Atlantic sea surface temperatures. In addition, stronger trades usually indicate increased vertical wind shear in the tropical Atlantic.

3) A decrease in tropical Atlantic sea surface temperatures. Cooler Atlantic SSTAs (sea surface temperature anomalies) provide less latent heat (i.e., less fuel) for developing tropical cyclones.

4) An increase in Pacific eastern equatorial SSTAs. Sea surface temperatures have still not reached El Niño levels; however, increased warming implies a shift in tropical convection towards the dateline. This eastward-shifted convection often increases vertical wind shear over the tropical Atlantic.

We're not out of the woods yet; it only takes one hurricane to cause incredible damage. But this seems like just one more sign that this hurricane season will not be at all like 2005, even if it's still projected to be an above average season by historical standards. Let's see what the British forecasters have to say tomorrow....

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Apologies for such a trivial comment, but I got stuck on your post title because I first parsed the phrase "gray scale" and couldn't figure out how monochrome graphics could "back the forecast".

So far so good. Last year by Aug. 4 there were already 8 named storms and 2 intense hurricanes! It's remarkable that no one predicted that so many of the factors conducive to cyclogenesis would be so significantly "worse" (from the storm's POV) this year. I wonder if there are other underlying factor(s) at play here; i.e. could there be some global "cause" for all of these factors to favour inhibition, similar to EN/LN?

Chris has done a good job of listing some of the known factors that contribute to the forming of cyclonic storms in the Atlantic basin. The fact is that there is no "formula" that can predict hurricane strength or likely formation.

I consider the scientists that are investigating the connection between possible anthropogenic global warming and hurricanes to be forthright and diligent. The problem is that there are many groups and organizations eager to use any information, either way, to their political advantage.

This makes climate science somewhat unique. In most disciplines the investigation will turn one way then another while asymptotically approaching a clearer picture of the phenomenon being studied. Presently opportunists lurk, waiting to "cherry pick" fresh information to compel public policy.

This puts great pressure on scientists to consider the moral and political implications of their work. It also presents an opportunity for some scientists to enjoy celebrity status, attending fundraisers and movie premiers alongside movie stars and other public figures.

I'm not sure this is a healthy environment for dispassionate scientific investigation, but it is the current situation and makes for good blogging!

By Lance Harting (not verified) on 04 Aug 2006 #permalink

The fact is that there is no "formula" that can predict hurricane strength or likely formation.

Well, thank you Captain Obvious!

The problem is that there are many groups and organizations eager to use any information, either way, to their political advantage.

Really? That's so unusual!

Presently opportunists lurk, waiting to "cherry pick" fresh information to compel public policy.

Hold the presses! I think Lance is on to something here!

This puts great pressure on scientists to consider the moral and political implications of their work.

Well, it's about time! For decades we've been suffering the amoral, anarchic, cold-hearted scientists and we've barely survived! I am truly hopeful they will read this thread and heed the sage advice!

It also presents an opportunity for some scientists to enjoy celebrity status, attending fundraisers and movie premiers alongside movie stars and other public figures.

See? There it is! What better evidence do you need? Not only are they amoral, anarchic and cold-hearted, but most probably...libertines!! And you know, when scientists begin hob-nobbing with "movie stars and other public figures", scientific rigor falls into great peril! Back to the laboratory for you Dr. Sky-Is-Falling!!

It is becoming all too obvious that Lance is every bit the "troll" he's been accused of in other threads. Sad and pathetic, but apparently true.

By evolvealready (not verified) on 05 Aug 2006 #permalink