The model guidance is beginning to hone in onto the potential for tropical development next week. Even the National Hurricane Center has latched onto that idea, highlighting an area of disturbed weather over the western Caribbean Sea with a 30% chance of development within the next 5 days, as of Wednesday afternoon.
At this time, there is a region of unsettled weather and an enhancement in showers and thunderstorms near Central America and over the Caribbean Sea. This is associated with the Central American Gyre, which is basically a large, broad area of low pressure. As we look farther out into time to next week, there is the potential for a more discrete area of low pressure to form either over the northwestern Caribbean Sea, southwestern Atlantic Ocean, or the Gulf of Mexico. That all depends on whether the thunderstorms organize around a center and if environmental conditions are conducive for a low pressure to form, which it would therefore become classified as a tropical cyclone.
Sea surface temperatures are generally at their warmest this time of year in this part of the world, but that doesn’t mean a tropical depression, tropical storm, or hurricane will develop. Wind shear is a big factor when determining tropical cyclone genesis. Wind shear is not liked by these cyclones because it rips their thunderstorms apart and doesn’t allow them to rotate around the low pressure center. Forecasting wind shear is not accurate looking over a week out in time, but there is some model guidance that does think the environment will be conducive for a tropical depression or storm to form. The current ensemble guidance from the European model suggests up to a near-50 percent chance a weak tropical cyclone arises somewhere in the Gulf of Mexico or southeastern Atlantic Ocean.
Now in terms of climatology, history suggests tropical cyclone formation is the most likely in this region where the area to watch is located: the western Caribbean Sea. Based off data from the National Hurricane Center’s Tropical Cyclone Climatology page, dozens of tropical cyclones have formed over the western Caribbean Sea, then take a track to the north toward the eastern Gulf of Mexico, US East Coast, of the western Atlantic Ocean.
According to Senior Research Associate Brian McNoldy at the University of Miami, South Florida is most hit by hurricanes during the month of October:
Historically, more hurricanes have passed near #Miami during October than during any other month. Storms that impact us this late in the season almost always form in the western Caribbean Sea and approach from the southwest. #hurricaneseason #flwx pic.twitter.com/zRAafaARl0
— Brian McNoldy (@BMcNoldy) October 1, 2018
This doesn’t mean a hurricane is headed toward Florida, but the forecast is worth monitoring, especially next week, across the Gulf Coast, Southeast, and southwestern Atlantic Ocean. Nonetheless, heavy rain and gusty winds can be expected in some areas.