Updated Sunday 1:14 pm
The tropics remain active, and the Gulf Coast of the United States now faces a hurricane threat this week. The models started hinting at potential development last week. At the time of writing Sunday morning, the storm was a Tropical Depression (TD #14). The storm has been designated Tropical Storm Michael (as of Sunday early afternoon), and models are suggesting that the storm will reach minimal hurricane strength (perhaps stronger) by landfall. Here is the latest information on why Gulf Coast states and parts of the Southeast need to pay attention.
The storm had its origins as a low pressure system east-southeast of the Yucatan peninsula. The mass of clouds associated with the low has become more organized in recent days. The National Hurricane Center forecast guidance as of 4 am CDT Sunday morning notes,
all indications are that the depression will gradually strengthen while it moves northward over
the Gulf of Mexico. In fact, nearly every piece of intensity guidance brings the cyclone to hurricane strength before it reaches land, including the GFS, ECMWF, and UKMET global models...Storm surge, rainfall, and wind impacts are possible over portions of the northern Gulf Coast by mid-week, although it is too soon to specify the exact location and magnitude of these impacts. Residents in these areas should monitor the progress of
this system
If there is one thing that I hope the public learned from Hurricane Florence, it is to consider the full range of impacts rather than focusing on the category of the storm. A few models, like the H-WRF shown above, hint at a potentially stronger storm, but it is important to remember that intensity forecasts are typically less reliable than track forecasts this far out from landfall. In the next several hours, the storm will encounter significant wind shear. Wind shear (changes in wind speed or direction with altitude) hinder storm development. However, the storm will eventually move into an upper level environment a more conducive to development. There are also plenty of warm water (29 deg C or higher sea surface temperatures) beneath the storm's projected track.
Parts of the southeastern United States, even inland, should also pay close attention to the storm because it is likely to remain at tropical storm force strength well after landfall. The American GFS model brings a fairly organized system directly over the Atlanta, Georgia area. However, the European model (not shown) takes the storm into southern Georgia. This will require close monitoring in the next few days. Parts of Georgia, the Carolinas, and Virginia could see tropical storm force winds and 3 to 6 inches of rainfall (see below). I am a professor at the University of Georgia. It located in Athens, Georgia, which looks to be very close to the maximum projected rainfall swath at this time.
If you are wondering about where hurricanes typically form during the month of October, this system formed in almost the exact region that climatological analyses would expect: the Bay of Campeche, western Caribbean, and southern Gulf of Mexico. The Gulf Coast, Florida, and southern United States are more vulnerable to hurricanes at this time of the year. October is often the last push for hurricane activity because the fall season jet stream patterns typically bring atmospheric conditions, most notably wind shear, less conducive for hurricane development.
Whatever happens in the Gulf of Mexico this week, our models have given us plenty of lead time to prepare. I still think the intensity potential of this storm bears a close eye. As my colleague, former Weather Channel and current FEMA hurricane expert Michael Lowry perfectly tweeted, "October storms require extra babysitting." My advice is to continue to monitor the National Hurricane Center and other credible sources. It could be a busy week for forecasters, emergency managers, decision-makers and people along the eastern Gulf of Mexico coast.
