Update Archive

Bertha Likely to Recurve...However...

Bertha Advisories from the NHC

Monday, 7/7/2008 - 4:30PM EDT

Most of the reliable global models NHC hurricane models (save the BAM suite) are on a recurvature scenario for Bertha, and to me this scenario seems to be the most likely outcome.

Bertha is significantly stronger than any of the models anticipated in previous runs. As a result it is firmly entrenched in the mean steering layer (500mb). The GFS has slowed down on the forward progress of Bertha in each of the last few runs, and now the 12Z Euro, with a significantly stronger cyclone on the grid is turning Bertha out as well. In fact, none of the 12Z global models get Bertha past 65W.

All of the global models are forecasting a short-wave trough to pass off of the east coast in 2 days. This shortwave trough is going to erode the western edge of the subtropical ridge just enough to create an opening for Bertha to find a way out of the tropics. If Bertha were weaker it could miss this “vent” but chances are good now that it will not.

The BAM models are taking Bertha on a more westward course…suggesting that the hurricane could miss the weakness in the ridge. For now, we have to discount this solution because they tend not to do well outside of the tropics.

Of course…the models could be overdoing the turn much like they have since 2004. I think there is a telling waypoint in terms of Lat/Long pairs that we can use to see if the model idea is playing out or not: by Wednesday afternoon, where will it be relative to 25.0N 60.0W?

If Bertha is a little south of this point (if it crosses 60W a little south of 25N) we may have a small window for a slowdown/stall. This also indicates the trough in the steering layer isn’t weakening the ridge as much as forecast. If Bertha is WAY south of that (say near 22.5 and 60.0) then the BAM models may be on to something and the whole forecast idea will need to be redone. On the other hand, if it is north of 25N before it reaches 60W, then the recurvature idea is almost assured, although they should keep an eye open up in Canada.

To learn more about hurricane preparedness, CLICK HERE.

MW

Listen Live on your Cell Phone!