Posted: Wed Dec 13, 2006 12:24 pm Post subject: Tropical Cyclone forecasting.
December forecasts for the next Hurricane season should be accepted for what they are,... educated guesses. Some are much more educated than others, while many are just flat out attempts to garner media attention and/or subscribers to boost profits. Let's go back to the 2004 season. Who could have predicted that Florida would be hit by Charley, Francis, Ivan, and Jeanne? No one. All the pre-season dire predictions were that Texas could/would be the likliest target. Wrong. Next was the complete failure in seeing the coming catastrophic season of 2005. Sure, a busy season was anticipated but who had foreseen the record breaking horrific nightmare that 2006 was to be? No one. That brings us to the 2006 season.
Basing their forecasts on what they had seen take place in 2005, anticipating conditions somewhat similiar, a forecast of above normal TC activity was issued by most all of the experts and agencies that matter, and those the public pays attention to. The outcome was once again wrong.
Forecasting Tropical Cyclone Genesis is very difficult. How many times during the 2006 season did you hear about possible tropical development only to have no development take place? The answer is dozens of times. The mentioning of possible TC development came from many sources including the NHC, NWS local forecasters, private sector meteorologists, TV weatherman and many hobbyists including myself.
Along with all the known ingrediants necessary to achieve TC genesis such as surface low pressure, warm sea surface temps at or above 80 degrees, favorable upper level winds, a moist environment, high pressure above the developing system, no interference from a land mass, etc, etc, there are other factors which are still unknown. These unknown factors play a huge role in the approx 90% failure rate in forecasting TC genesis. Many times I have seen a potential system in it's embryonic stage that appeared to have all the necessary environmental conditions available to develop, but yet it failed to do so. Why? It's those unknowns that have yet to be identified.
During the 2003 season I received an e-mail from a Hurricane Specialist at the NHC alerting me to watch a disturbance that was still inland over Africa and was not to move off-shore of the African coast for at least another 24 hours. The HS went on to say that this disturbance will "likely" develop into a Hurricane and has a "good chance" of becoming a Cat 5. My jaw dropped when I read that. I was amazed that an HS at the NHC would go that far out on the ledge to predict a Cat 5 well before there even was a Tropical Depression. As it turned out the disturbance moved off the African coast, became a depression, intensified into a Tropical Storm, shortly thereafter a Hurricane, and eventually became CAT 5 Hurricane Isabel. To this day I don't know exactly what he had seen before hand to make that bold prediction, but I do know that many other systems that appeared to have the same conditions available did not develop to anything more severe than your run of the mill Cat 1 or 2, and others didn't even achieve Hurricane intensity. This is where those unknown factors come into play regarding TC Genesis.
The unknown factors also play a big part in continuing failures associated with TC intensity forecasts of already developed Tropical Cyclones. One only has to look at the life cycle of Hurricane Wilma to see the effects of the 'unknowns'. Hurricane Wilma's jaw dropping record breaking intensification cycle that took place in just a few hours, and was not anticipated, is still being studied as the prime example of what those unknown factors are capable of doing. There are just too many things, many known and many unknown, that make even short term TC forecasting very difficult. Trying to predict how many storms there will be 6 months before Hurricane season, where the highest risk of landfall is, and the number of major Hurricanes, is very very unreliable. Even forecasts that are issued at the beginning and DURING the season have a high rate of error.
Tropical Cyclones, for all their power, fury, and relative size, are very fragile creatures. Many negative environmental conditions such as wind shear that disrupts vertical development of the thunderstorms necessary for a TC to intensify, cool sea surface temperatures that inhibit growth of wannabe systems or weaken already developed TC's, dry air intrusion into the central core of a TC, influence from an upper level low which can completley "decouple" the surface low pressure center from the mid-level center, or doesn't allow the system to be vertically stacked thoughout the layers of the atmosphere, and a TC's worst nightmare...Land. Now add the things we don't know and it's clear to see that there are many factors that make TC forecasting a very inexact science. While great strides have been made over the years with respect to TC forecasting, the NHC is the first to say that any track forecasts beyond 72 hours is not reliable, intensity forecasting is still riddled with unknowns, and long range TC forecasting is still somewhat of a fantasy. I can't tell you what the 2007 Hurricane season will bring, but I can tell you what I would like to see. Another season just like 2006. Sorry to be so long winded and hope I wasn't boring.
Joined: Jun 08, 2005 Posts: 3341 Location: Cape Coral, Florida
Posted: Sat Dec 16, 2006 4:08 pm Post subject: Re: Tropical Cyclone forecasting.
Great article Lou and I found it very informing. You are right though about the long range forecasting. The 2006 season was very inactive when compared to the forecasting the NHC issued before the season even started. It was almost non-existent with hardly any land-threat storms. I'm assuming the reason why the NHC was basing heavy hurricane activity in 2006 was because of what took place in 2005 and 06. I could be wrong but that's just what I think. To be able to predict a season 6 months before it starts does seem like a fantasy. I don't think it's possible. You could make an educated guess but again it's only a guess and nobody will no for sure because of all the unknowns that you mentioned. A lot of the unknown factors were definitely in place for 06' and it would be really nice to see them show up again so we don't have to repeat what took place a few years ago. It was nice to not have to put the shutters up again. _________________ Chris
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