"Dorian" Rolling West Over Open Atlantic....
-- like several of the early season storms this year -- continues to speed westward near 20 mph. No change in the speed is likely until late week/this weekend when the storm rounds the southwest periphery of the large Bermuda high over the N. Atlantic. The relatively small storm is pretty well organized with even some occasional hints at a weak mid level eye trying to form. However, the road ahead remains bumpy to say the least though the small size might help it survive to some degree. The fast movement generally does not favor rapid intensification. Maps below show the pitfalls ahead for "Dorian" including:
** A huge slug of very dry mid & upper level air is ahead over the Central Atlantic -- see the water vapor image -- 5th image below. The rust color is extremely dry air.
** The next image shows sea surface temps. which are a bit marginal -- though not prohibitive -- for a tropical cyclone -- a nose of near 80 degree water extends southwest from the E. Atlantic before sea surface temps. again increase. The fast movement & small size of "Dorian" should limit the effects of the cooler water temps.
** Lastly -- but perhaps most significant .... while in a low shear environment for the moment, wind shear picks up dramatically over the Central Atlantic between Puerto Rico & about 50 degrees W (see last image below). There is then a small area of much lower shear followed by another area of high southwesterly shear environment over the W. Atlantic in association with a persistent upper level trough near the U.S. east coast.
Indeed...global forecast models are not particularly enthusiastic about this system...& with good reason. At this point, the NHC maintains a tropical storm to north of Puerto Rico by early next week. At least some semblance of an upper level trough still looks to be over the Western Atlantic next week (roughly where there is a trough now - see 4th satellite image below) which would probably continue/reinforce shear & also encourage a northwest or north turn (with the strong Bermuda high fairly far to the east/northeast over the Atlantic) in the long term. The shallow (weak) nature of the system -- if "Dorian" remains weak -- should allow the system to move along quickly...possibly steered more by the low level winds vs. mid/upper level flow....unless there is more strengthening than I currently expect. This implies more west/northwest movement next week as the European model has been indicating placing a weak system -- possibly merely a wave -- near Fl. about midweek. The GFS model has been bouncing back & forth between a stronger system & a weak one &, therefore, has been more inconsistent on a track. When a model run shows a stronger "Dorian", the track is more north with earlier recurvature....when showing a weaker system then a more west movement. I will say the GFS has seemed to better initialize "Dorian" & did an excellent job on its genesis.So....at this point...
.I remain on the side of "Dorian" being relatively weak once it moves or tries to move into the SW Atlantic next week. IF there were to be any effects on the First Coast, it would be the middle &/or end of next week & these effects -- right now
-- would appear to be relatively minor.It should be emphasized
that it's still early in the forecast on this storm, & the American GFS model last week was showing a stronger tropical cyclone near Puerto Rico, so it's too early to completely write off "Dorian" & how strong it might -- or might not -- become....as well as the track next week once closer to the Caribbean & SW Atlantic.
Another tropical wave is moving off the coast of Africa at a bit higher latitude than "Dorian". Development of this wave appears unlikely.
Forecast models plot below courtesy S. Fl. Water Management District (excellent agreement into early next week)....ultimate forecast will hinge on the trough remaining near the east coast which would tend to cause recurvature -- to at least some degree -- ... & whether or not "Dorian" can survive the generally hostile environment (shear) it will encounter in the long term.