Discussion about models,patterns and seasonal forecasts

[Stormsfury]

The majority of the models had Isabel pegged at hitting the EC in the MidAtlantic. The biggest problem was with the strength which FORTUNATELY was alot less than what she had originally grown to.

Yes Steph last year the forecast of the tracks was very good as I mentioned with Isabel and SF mentioned Claudette but still about forecasting intensity there is a ways to go and an example was Isabel at it's early formation how the forecast of the intensity was not so good that Isabel went from a wave to a hurricane in 2 days.

Good point that Luis brings up ... Intensity forecasts are simply the hardest to gauge and forecast ... there are so many small scale features that are happening continuously and various many factors that go into the process of trying to determine intensity forecasts, and they are FAR from perfect ...

Mesoscale features can cause a sudden burst of rapid intensification such as a warm water eddy, or a s/w ridge over the top of a TC (even for a brief period), or in Isabel's case, the appearance of Rossby Waves ... (or the swirls/mesovortices embedded within the larger scale eye.) ... and also, not to forget in stronger hurricanes, the eyewall replacement cycle, and this is only a few of the many factors that have to go into TC intensity forecasting ... let's not forget Hurricane Heat Potential (which in 98% of TC's are never realized) ...

Here's a PDF flie from AMS regarding estimations of Tropical Cyclone Strength...

http://ams.confex.com/ams/pdfpapers/72763.pdf

In Floyd's case, and also with Opal's case ... both passed over very warm eddies (In Floyd's case, I believe it was 32ºC water ... and in Opal's, well I can't quite remember, but I link this from the AOML page concerning this ...

Hurricane Opal in the Gulf of Mexico, August-September 1995 (left):
This TC intensified from hurricane-1 (74-95 mph winds) to hurricane 4 (131-155 mph winds) while traveling over a number of warm features in the Gulf of Mexico. In particular, this TC suddenly intensified from hurricane-2 (96-110 mph winds) to hurricane-4 in a period of 10 hours when its track went over a very well defined ring with a mean radius of 150 km that had been shed by the Loop Current. Altimeter-derived fields indicate that the increase in TCHP associated with this warm ring was approximately 30 kJ/cm2. The most striking information of the ocean conditions during the life span of this hurricane over the Gulf of Mexico was that this warm ring was not detected using the AVHRR-derived sea surface temperature fields.




Lili was a PRIME example of a rapid intensification stage, but quickly followed by an almost and just as rapid weakening phase just before landfall ... and just how hard it is to gauge when such cycles will occur ...

And unfortunately, I've lost my link to a page regarding Parameters for Rapid Intensification Paramaters ... I'll try to find those ...

SF

[cycloneye]

Also it is difficult to forecast with presicion the shear factor and the dry air as many cases haved shown in past years.Georges was a good example of a cane that was almost a cat 5 east of Guadeloupe and then it weakened to a cat 2 bordering a 3 as it crossed the leewards and made landfall at PR.Unexpected shear and some dry air penetrated the core of the hurricane to weaken it and that was not forecasted by the models nor TPC at that time.As I mentioned before forecasting intensity has a ways to go as there are many variables that will weaken or intensifie a system in short notice and damp a projected forecast.

[MGC]

I for one was pleased with the NHC 5 day forecasts. What has made this possible? Increased computing power. The ability to crunch numbers is increasing by the day due to technological gains. This mathematical ability coupled with better model programms will continue to yield more precise forecasts. Count on it......MGC

[mf_dolphin]

I have to agree MGC. I look forward to another year of the 5-day forecasts. It really gives you a good visual on what the NHC is thinking.

[Stormsfury]

I for one was pleased with the NHC 5 day forecasts. What has made this possible? Increased computing power. The ability to crunch numbers is increasing by the day due to technological gains. This mathematical ability coupled with better model programms will continue to yield more precise forecasts. Count on it......MGC

The 5 day forecasts were surprisingly very good this year, and is a testament to the research and for other reasons, including those you specified ... good post, MGC.

SF

[cycloneye]

I also agree with MGC about the 5 day forecast.My take on the 5 day forecast is that it came to stay forever as new technology comes in and improve it.

[cycloneye]

I think that this thread has a great discussion going on so I bumped it to see if anyone will discuss more about the themes that this thread has.It has many educational things for the non-experts to read about and know more and more about tropical weather.

[Rainband]

I agree about the 5 day. It helps people who aren't in the know, to understand more clearly whats going on, and helps people get a pretty good idea if they need to start preparing earlier than before

[cycloneye]

I agree about the 5 day. It helps people who aren't in the know, to understand more clearly whats going on, and helps people get a pretty good idea if they need to start preparing earlier than before

I also like the 5 day forecast guidance because you can see what is going on and also you can see what factors will lead a tropical storm or a hurricane to track as the guidance says it will go to.And of course the 5 day forecast makes people pay attention from very early to a system to see it's progress.