Monday, June 06, 2011

Caribbean Blobette; June 6, Update A

A short update today:

This blobette is more than a little drunk on rum I think, so it’s not quite able to get its act together. There continues to be some low level circulation, mostly off the coast of Nicaragua/Honduras. There is also some heavy convection, mostly over Nicaragua/Honduras at the moment. However the two are not really aligned, and the upper level circulation is quite far removed from this any of activity. The wind shear is strong enough to inhibit this from developing much so unless it drinks a few strong cups of coffee, I’m not going to bother writing any more on this blobette.

Instead, I’ll take a bit of your time to answer a question from *cough* September 2010 *cough* (I’m a bit slow sometimes… ;-)). This was sent to me by Chris H. (question 1 of 4... I'll try and get around to answering the other three sometimes in the next 5 years).

Is the scientific community any better at predicting hurricane paths than it was in 1995? Is it possible to say "we can predict the path of a hurricane with x% more certainty than we could back then?"

Despite my ‘slight’ sarcasm about model forecast tracks drawn by 2 year-olds etc, the answer is yes! The scientific community has definitely improved its ability to predict hurricane paths over the last ~15 years. Like any good geeky scientist-type (and proud of it), I shall resort to showing you a graph that summarizes the improvement:

This shows the error in track forecasts from 1970 to about 2007. Each colour (please note correct British use of extra ‘u’) line represents the forecast at a different time, so the red is the 24 hour forecast, the yellow is the forecast at 72 hours (normally known as the 3 day forecast of course), and the blue is the 5 day (120 hour) forecast. There are a few things of interest in this:

1. The 24 hour track error in the early 1970s was about 100-150 nautical miles (1 nmi = 1.15 miles), but in the early 2000s, it had come down to around 50-75 nmi.

2. The 4 and 5 day track forecasts only really began in the early 2000s, and the track error at those lead times was comparable to the 2 and 3 day forecasts in the 1970s.

3. The variation in the error from one year to the next was much bigger before the 1990s, but is smaller now.

Ha, Chris, I bet you weren’t expecting an answer (apparently no one expects the Spanish Inquisition either ;-)).

That’s it for today. I’ll answer another one of your fabulous questions soon(ish).


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These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.

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