97L is looking more organized in the western Atlantic as of Tuesday afternoon and is likely going to be Tropical Storm Matthew soon. There is still MUCH speculation as to where the storm will go once it gets into the Caribbean. I do want to emphasize there is absolutely no need to panic or be worried about this. It is a storm, however, that needs to be watched carefully in the coming days.
One thing is for certain, it will likely become a formidable storm once it gets going. The rather broad rotation associated with the cloud mass will gradually tighten up over the next 24-48 hours as it tracks westward through the Windward Islands. Right now it appears the westward movement will continue through the end of the week with the storm gradually strengthening with time. Hurricane Hunters investigated the system Tuesday afternoon and DID NOT find west winds on the south side of the area of rotation. As a result, there is no closed area of low pressure and will not be classified as a depression or storm at this time, even there are some tropical storm force winds associated with the disturbance.
There is still significant disagreement with the operational and the ensemble models as well as each individual operational model as to where Matthew will go next. There has been a trend within the last day or so to bring the track farther west closer to the U.S. East Coast.
If you remember in my previous entry that I wasn’t buying the early due north turn toward the Dominican Republic and Haiti then toward the Bahamas. That abrupt turn shown by most of the models since Sunday seemed suspect and I still feel that it is. I do feel that the system will track farther west before making any attempt to turn northward.
This will be the key in the coming days. How far west will the storm track before the north turn occurs? For Florida the storm would need to get as far west as 80°W longitude or more to pose a direct threat to the state. Depending on the eventual size of the overall wind field, even a turn between 75° and 80° could cause some issues for South Florida. This is of course assuming it moves due north once it makes the turn. A steady northwest motion after the turn would still put Florida in jeopardy of impacts especially in a storm with a large wind field.
Also keep in mind that this north turn will occur LATER if the storm doesn’t go bananas and intensifies significantly. More powerful storms are taller in the atmosphere and are more influenced by upper level steering currents as opposed to shorter weaker storms. So the strength of the system will also play a role in when this turn occurs.
Why is the north turn expected to occur at all? There is a large strong upper level low pressure over the Great Lakes that will dive southward into the Ohio Valley and meander through the mid-Atlantic through mid-week. A piece of this upper low will also break off and head southward toward the western Gulf. This will lead to a weakness in the large upper level high that is steering the storm westward. It is this weakness combined with the eventual strength of the system will determine how for west it gets and who will be impacted. Even a couple of hundred miles will make all the difference.
There is still plenty of time to watch this, but this is a storm we need to pay close attention to here in South Florida, especially given the recent trends. As things change we will be keeping you updated so be sure to check back! Special thanks again to TropicalTidbits.com and Levi Cowan for the forecast model graphics and UCAR for the spaghetti plots.
Chief Meteorologist Derek Beasley