Dr. Jeff Masters believes that “Invest 90L” will become Tropical Depression 4 tomorrow or Tuesday, and he thinks it will ultimately become Hurricane Dean, and a threat to North America. In a post this morning, he writes:
Watching the computer model runs for 90L is not for the faint of heart. All the major models except the NOGAPS develop the system into a tropical storm or hurricane that tracks westward over the Atlantic, reaching the lesser Antilles Islands as early as Thursday night, August 16. There are four possible scenarios to consider:
1) A strong trough of low pressure is forecast to move off the East Coast of the U.S. at that time, and this trough may deflect 90L northwards so that it misses the Lesser Antilles Islands, and then recurves harmlessly out to sea.
2) In keeping with the steering pattern we’ve observed since late July, the trough is expected to rapidly move onward, allowing a ridge of high pressure to build in. If the trough is not strong enough to recurve 90L out to sea, the storm will be forced to the west once more and eventually hit the East Coast of the U.S. This is the solution of last night’s ECMWF model.
3) 90L will be far enough south and next weekend’s trough will be weak enough that 90L will plow through the Caribbean, and not be deflected north of the Lesser Antilles Islands. The storm would eventually track into the Gulf of Mexico. This is the solution preferred by this morning’s GFS model.
4) 90L will never develop, or will never become more than a weak tropical storm, due to unfavorable wind shear, dry air, or other factors. This is the solution of the NOGAPS model.
Of the four scenarios, I believe #2 or #3 are most likely to occur–90L will develop into a tropical storm or hurricane that will affect the Caribbean and/or U.S. East Coast. Residents throughout the Caribbean and U.S. should anticipate the possibility that 90L may become a hurricane–and possibly a major hurricane–that will not recurve.
With regard to scenario #3, recall that the Gulf of Mexico is really, really warm right now, so it would be seriously bad news if any well-organized storm were to reach it.
Meanwhile, out in the Pacific, monster Category 4 Hurricane Flossie is expected to pass 50-100 miles south of the Big Island of Hawaii late Tuesday or Wednesday. She will have weakened by then, though, probably to a Cat. 1.