Friday, July 3, 2009

Hurricane Predictions

Predicting hurricane seasons is a bit like predicting next year's global economic developments - no matter how sophisticated your models, it's always a bit of a crapshoot, although judging by what I have been reading, we seem to be somewhat better at predicting hurricane trends than economic trends. Which is a bit funny considering that much of economics is based on the assumption that people act in a very predictable and rational way, while nature is generally described as a rather capricious lady. Hmm.

In any case, now that I am actually keeping track of things like shear winds, low-potential disturbances and tropical depressions, I have learnt that hurricanes seem to occur in cycles. Specifically, in 20 or so year cycles. The last cycle of high(er) activity started around 1995, hence we are about half way through the current active cycle. And so it appears to be not just global warming which is causing an increase in hurricanes (and there are those who say it is not actually causing an increase per se, just an increase in strength), but also the fact that we are now undergoing a naturally occurring period of higher hurricane activity. Add to that the ever increasing fascination of the media with hurricanes, and it's no wonder things all of a sudden seem a lot worse than, say, 50 years ago.

But it looks like we might get a bit of a break in 2009. Over the last year we have lived here, we have come to rely on two websites to get hurricane information: and The former is a pretty flashy looking website with excellent tracking and GPS information, while the latter has a much more scientific feel to it, with lots of scientific articles and a blog by its founder Dr. Jeff Masters, who has a lot of expertise in this area. In his recent blog on the July hurricane outlook he mentions something I also noticed over the winter - it was very windy. Apparently this has also had an effect on sea surface temperatures:

"Stronger-than-average trade winds were observed through most of the period November 2008 - May 2009, which helped cool the tropical Atlantic substantially. Strong winds mix up colder water from the depths and cause greater evaporative cooling. ... July storms typically form when a cold front moves off the U.S. coast and stalls out, with the old frontal boundary serving as a focal point for development of a tropical disturbance. There will be one or two fronts moving off the U.S. coast over the next two weeks, and we will need to watch these for development. Wind shear is too high and SSTs are usually too cold in July to allow African tropical waves to develop into tropical storms. African tropical waves serve as the instigators of about 85% of all major hurricanes."

And it also appears that another El Nino is on its way. In Manitoba, the prospect of an El Nino was not particularly welcome, as it could mean less rain and possibly droughts. Down here, the news of an El Nino has a much more positive ring to it, at least hurricane-wise:

"El Niño conditions continue to amplify over the tropical Eastern Pacific. Ocean temperatures there rose 0.5°C over the past two weeks, and are now 0.45°C above the threshold for El Niño, according to the Australian Bureau of Meteorology (Figure 3). NOAA's Climate Prediction Center issued an El Niño Watch in early June, saying "that conditions are favorable for a transition from neutral to El Niño conditions during June - August 2009". The pattern of changes in surface winds, upper-level winds, sea surface temperatures, and deeper water heat content are all consistent with what has been observed during previous developing El Niños, and latest set of mid-June runs of the El Niño computer models are almost universally calling for El Niño conditions to become well-established for the peak months of hurricane season, August - October. It is likely that Atlantic hurricane activity will be suppressed in 2009 due to the strong upper-level winds and resulting wind shear an El Niño event usually brings to the tropical Atlantic."

If he is right, I won't have to rush off to stock up on cans of Vienna sausages anytime soon.

No comments: