2004-09-03 FCST: Ivan (Atlantic)

Why does the GFS output (using NCAR) show the low pressure of Ivan in the near term much higher, then progs lots of strengthening as it moves NE along the east coast (which would be cooler waters, right??)? Or am I missing something here? Granted, I used to do "OK" at forecasting a couple of years ago but I don't try anymore because I simply don't have time.... so I certainly may be interpreting this incorrectly.

Thx.
 
Many operational models greatly underinitialize tropical systems (hurricane Ivan included). I think the only one that I can recall that usually at least comes close to initializing hurricanes well is the GFDL. Given the favorable environment in the forecast path of Ivan, the models then deepen the storm from a plain-jane Low pressure system to a significant storm...

Ivan took a little jog to the west a couple of hours ago... Convection has again become very intense and symmetric about the eye, so there is little doubt in my mind that it remains as strong as it was earlier this morning...
 
Yes, each model run has to basically build the hurricane from scratch (i.e. from a warm-cored tropical low). This is why GFS is not used for intensity forecasts but rather for position forecasts.
 
Why the dog leg and the sharp right to florida

Looking at the track of Ivan, so far its to the northwest. I am just curious why all the models show a turn to the right some time in the future towards florida. If you look at the surface maps there are no steering high pressure systems in the central or south central us at this time or in the near future. Unless its something I am missing, I would be more worried for alabama and westwerd.
 
Layers above the surface, where the hurricane gets its steering, show a gradual weakening of the anticyclone holding Ivan southward. All the same, the trend has been to cluster model guidance and push the track westward as somewhat higher heights to the north of the storm are initialized in.

Unfortunately for Jamaica, Cuba, and west Florida, it looks more and more like a slo-mo version of Charlie. A beast like Ivan ambling its way across the narrow neck of Cuba and into the GoM with low shear and 30C water isn't a pretty picture for some place along the gulf coast. Hopefully it will start ambling soon enough to be somewhat chewed up by Cuba.
 
2145Z vortex report: 920Mb, 144kt FL wind

Still steaming big time. I'm a little surprised given the somewhat cooler water east of 75W, but Ivan looks pretty fat and happy right now. Still got its beady eye on Jamaica, pour souls. :(
 
I think it's going east

If you look at the upper level jet, a trough develops along the central gulf coast. This should steer Ivan to the northeast. I think the hurricane center's track is too far west! I wouldn't be suprised if the hurricane hit south florida and then turned northward along the east coast.
 
Re: I think it's going east

If you look at the upper level jet, a trough develops along the central gulf coast. This should steer Ivan to the northeast. I think the hurricane center's track is too far west! I wouldn't be suprised if the hurricane hit south florida and then turned northward along the east coast.
Click to expand...

Personally, I prefer the more westward forecast track... I think the NOGAPS and UKMET models have performed very well lately (e.g. with Frances), and both of those models have generally been on the west side of the guidance packages. SSTs warm consistently along Ivan's track, so cold water won't be an issue. I'm assuming the slightly cooler waters along the northwest FL coast (courtesy of then-TS Frances) will be gone in 4-5 days. I do think, however, that if the trough along the Gulf Coast as is strong or as south as most models currently depict, Ivan will likely incur signficant shearing as it enter the Gulf, which could have a big impact on the intensity of Ivan when it hits land... And yes, it seems pretty apparent that it's a "when" issue and no longer an "if" issue. The big issue now is southern FL, western FL, or southern AL? All models agree that the trough will be deep enough to prevent Ivan from making it into the central or western Gulf, which I agree with. Official forecasts (NHC/HPC) bring the storm onland north of Tampa. But again, upper-level flow could be rather harsh in the northern Gulf by that time, so...
 
I hope this is the right place to ask this...if not, I apologize in advance.

Why is there so much lightning in Ivan's eyewall? From what I read, isn't that supposed to be unusual? Is it because of stronger updrafts in these thunderclouds?

:shock:
 
The 00z GFS is a little futher west. I do agree about shear. It is looking more likley that IVAN will hit Florida. I doubt it would go as far west as Alabama. It's too early to tell, but it could be similar to Charlie.
 
Ivan's now back to cat-4, but a strong one, with winds of 145 mph and pressure 930 mb. Interesting to see that on the satellite image, the edge of the eye has sort of softened — it's symmetrical, but it looks to be sort of crumbling out to about double the radius of the eye already . . . perhaps the eye is enlarging, or it's starting the whole recycle process; that might be a good thing, at least for Jamaica.
 
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