After a decade of relative inactivity, the tropics are presenting Florida with the single greatest hurricane threat since the landfall of Major Hurricane Wilma in October 2005. The length of time that has gone by without a major storm is concerning in itself as the state has accumulated nearly 2.5 million new residents that may not know how seriously to handle a major landfalling hurricane. The level of preparedness will be highly dependent on how this threat is conveyed to the public by meteorologists and emergency management officials. Proper communication will be even more crucial With a track that will likely parallel much of the east coast of Florida. Just a few miles difference east to west in track can change overall impacts substantially. It may make all the difference between some areas observing tropical storm or major hurricane force winds.
The following animation may help demonstrate how subtle changes in the regional synoptic weather pattern can make or break anticipated forecast conditions along coastal Florida. This loop displays the last eight American GFS model forecasts or runs valid for 2AM EDT Friday, October 7th. If one looks closely, there are a couple noteworthy trends. First, the longwave upper trough approaching from the Midwest US is not as “deep”, and is located farther north. Second, the Atlantic subtropical ridge along the Southeast US coast is slightly stronger, and extends farther inland as a result of the changing orientation of the trough upstream. This stronger ridge very well could allow the inner core of Matthew, the region of the storm containing the strongest winds, to move directly over the coast before turning northeast. Several of the most recent cycles of the other two most reliable global models, the ECMWF and UKMET, have trended in the same direction. If today’s 12Z model cycle consensus holds onto this solution, I suspect the National Hurricane Center will shift their track ever so slightly to the west.
If the short term forecast uncertainty isn’t enough, models have also begun to throw a wrench into the three to five day forecast time frame. With the aforementioned trough not being quite as robust as initially projected, there is a growing probability that the mid-latitude feature will fail to turn Matthew northeast, and fully out to sea following a Floridian landfall. Instead, Matthew may be left behind as mid-level ridging attempts to re-develop to its north and east. Residents along the Southeast US coast and Bahamas may need to monitor Matthew for at least another five to seven days. Some guidance even suggests the storm may even attempt to head back towards Florida if the surrounding ridging returns with enough vigor. This is a scenario that will have to be watched, but climatology suggests that Matthew will eventually either recurve ahead of another oncoming trough, or dissipate as it encounters moderate southwesterlies aloft. Interesting days lie ahead.