Excellent analysis on steering curents by Jeff Masters 7/27

[cheezyWXguy]

I think the GFS gets rid of it in a few days to a week from now, although I havent looked at it in a few hours, but if thats the case, then the pattern will change just in time for august

[Sanibel]

There's a giant ULL over the east and some kind of W-E oriented shortwave up along the Canada border above the Dakotas that isn't pushing too fast. The ULL is spinning shear onto that disturbance in the GOM. Doesn't look to be clearing anytime too quickly. No definite Bermuda High pattern just yet.

[windstorm99]

Great stuff from jeff masters once again on the next 2 weeks steering forcast....7/27/07

The hurricane steering pattern for the next two weeks over the North Atlantic should be near normal, with no areas at above-average risk for a hurricane strike. The tool I like to use to study steering currents is the 500 millibar (mb) upper-air forecast from the latest run of the GFS model. Plotted on these maps are lines showing how high above sea level one finds a pressure of 500 mb. Where a U-shaped bend occurs, a trough of low pressure is present. Any tropical cyclones that get far enough north to "feel" the trough's presence will recurve to the north. Conversely, an upside-down "U" in the 500 mb height lines reveals the presence of a ridge of high pressure. Ridges force tropical cyclones to move westward (in the Northern Hemisphere.) As seen in Figure 1, a ridge of high pressure was present this morning over the U.S. East Coast, with troughs of low pressure over the mid-Atlantic and Great Lakes. Under this steering pattern, any hurricanes in the mid-Atlantic north of about 25 degrees latitude would be recurved by the mid-Atlantic trough, but storms closer to the U.S. would not get recurved until they came very close to the coast and began feeling the Great Lakes trough. One can pull up a loop going out a full 16 days of the 500 mb forecast and watch the evolution of the trough/ridge pattern to see how the steering currents might change.



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