00:00 UTC tropical Model Suite

[ameriwx2003]

http://twister.sbs.ohio-state.edu/text/ ... s/03091500

[Rainband]

Thanks

[wxman57]

One thing to remember about the BAMM/BAMD (ignore NHC98 as that's just climo based, and LBAR which rarely has a clue) is that these models are not very "dynamical" like the purely dynamical models (GFS, ECMWF, NOGAPS, etc). Basically these two models predict where a storm will go by first removing its circulation from the general mid and upper-level flow. The then look at the underlying flow patterns and project where the "river of air" will take the storm. Now this technique can work very well in the lower tropics - south of 20N, because the atmosphere is fairly static. There are no frontal systems down there. But north of 20N, the atmosphere is by no means static. There are frequent changes in the basic flow pattern (as we have along the east U.S. coast). Therefore, these two models may not project the storm's path properly in the mid latitudes.

That said, of the two models, the BAMD (deep layer model) would be the best choice for a storm like Isabel. Taking a look at the BAMD track, I see two things. First, it shows general slow-down in the next 12 hours - signs of a turn. Second, the turn is a bit more gradual than the current NHC track, taking Isabel inland into the NC coast near Cape Fear.

Now this westward shift COULD be due to the above-mentioned fact that the BAM models do not work well in a changing flow pattern. The BAMD may be assuming that the current flow off the SE U.S. coast may not change, ignoring the approaching trof. Therefore, the BAMD could have a left of track bias in such conditions.

However, I DO think that if the current track is off, it may be too far north. I'm a bit concerned that Isabel's turn may be delayed 6-12 hours. This could result in a landfall farther down the NC coast, maybe near Wilmington. Can't even rule out the northern SC coast. We'll just have to see where Isabel begins to turn.

Oh, and the first sign of a turn would be a slowing of Isabel's forward speed. Looking at the latest satellite loops, I THINK I can see such a slow-down now, but I'd like to see another 6 hours of movement before determining if the slow-down is for real.

[Rainband]

Thanks WXman57

[ameriwx2003]

Wxman57 good post and good explaination:):)

[Pebbles]

Would like to add my thanks for the explanation...lets me know which and why some models are more favorable with these types of storms when you got 5 or more lines staring you in the face

[ericinmia]

Those cords for the BAMD have it move at a good WNW - NW - NNW track:

1.1N and 1.3W in 12hrs
2.0N and 2.7W in 24hrs
2.7N and 2.9W in 36hrs
3.3N and 5.2W in 48hrs
6.0N and 6.8W in 72hrs
11.2N and 10.1W in 96hrs
18.5N and 13.0W in 120hrs