A State of Emergency has been declared for three states: Mississippi, Alabama, and Florida. This comes as Subtropical Storm Alberto prepares to make landfall on the western Florida Panhandle Monday afternoon, bringing heavy rain and flooding, tropical-storm-force winds, tornadoes, storm surge, and rough surf.
Alberto has likely peaked in strength since Sunday evening with an aircraft reconnaissance flight recorded sustained winds at one part of the storm to be at 65 mph. There is now loads of dry air containing to wrap around the storm while working toward its center, which will prevent much further strengthening. This dry air has also prevented Alberto from transitioning from subtropical to tropical, but either way the impacts will be the same.
Subtropical Storm Alberto will make landfall Monday afternoon or evening on the western Florida Panhandle between Pensacola and Panama City Beach likely as a 65 mph storm. It will then track inland through midweek, bringing heavy rains to portions of the Tennessee and Ohio River Valleys.
There are a multitude of threats Alberto will bring, including the flooding rains, strong winds, tornadoes, storm surge, and rough surf. We’ll break down each threat below.
Rain will be the biggest story with Alberto. Almost all of the Southeast will deal with at least a brief period of rain. Alberto will deliver a widespread one to three inches of rainfall to the Southeast now through Wednesday night. Three to eight-plus inches of rain is expected in those two areas, which includes the western Florida Panhandle and eastern Alabama and parts of the southern Appalachian Mountains.
This heavy rain will likely lead to flash flooding, especially where over five inches of rain falls. Much of this rain will fall in a short period of time, especially at the northern Gulf Coast. The Weather Prediction Center has this region in a high risk for flash flooding. This basically guarantees that some locations will indeed deal with flooding. Flooding is also a concern in South Florida. It’s been a very wet May and the month will end on a very wet note. In Miami, rainfall is over half a foot above average month-to-date. With additional rounds of rain and thunderstorms ahead through mid-next week from Alberto, that will allow for flooding due to the very saturated soil.
In terms of timing on Monday, the core of Alberto will move onshore, which will contain very heavy rain. Atmospheric moisture values will likely break records due to the loads of moisture this cyclone will carry. This core will primarily affect the western Florida Panhandle and southeastern Alabama during the day. In the remainder of the Southeast, there won’t be any organized rain. Instead, storms will be in the hit or miss, scattered variety. Then overnight Monday, the heavy rain surrounding the center of Alberto will become more scattered and disorganized due to the storm’s primary fuel source: the warm ocean waters. Therefore, rounds of heavy rain can be expected in the Florida Panhandle, Alabama, Georgia, and the southern Appalachian Mountains.
Now on Tuesday, the center of this storm will remain over Alabama. By this time period, the storm will have weakened into a tropical depression. This just means that winds will be weaker but the heavy rain will remain. Scattered showers and storms will work into portions of the Southeast coast and especially Florida associated with Alberto’s feeder bands. Meanwhile, the center of Alberto will move into the Tennessee River Valley, bringing in heavy rain to these areas.
During the latter half of the week, that rain will move into the Ohio River Valley, eastern Great Lakes, and parts of the Northeast and Mid-Atlantic. Localized areas may deal with flooding due to the pockets of heavy rain working into saturated soil.
The threat for flooding due to storm surge will exist with Alberto. The National Hurricane Center has placed the areas from the Suwannee River to Navarre, Florida under a Storm Surge Watch. This means there is a possibility of life-threatening inundation from rising water moving inland from the coastline in the indicated locations during the next 48 hours. This watch may be upgraded to a warning, but the confidence is low to moderate on whether this surge will actually occur.
All of these locations under the watch may experience coastal flooding. Two to four feet of surge is forecast for most of these locations.
As with most tropical cyclones, the threat for wind always exists. At this time, sustained winds are forecast to clock up to 65 mph at landfall. Significant damage from wind is not expected, and the strongest of winds will only affected an isolated area just east of the center of the low pressure. Wind gusts in some locations may reach 65 mph.
A Tropical Storm Warning has been issued from the Suwannee River to the Mississippi/Alabama border. This means that tropical storm conditions (winds greater than or equal to 39 mph) are expected in some parts of the warning area.
Brief tornadoes will be a risk with Alberto. As the storm moves to the north, the threat for tornadoes will follow. Our forecasters suggest that the risk for low-end tornadoes will exist across most of the Southeast, especially as this storm makes landfall on Monday. This Sunday, the risk will only exist in Florida as bands of thunderstorms move onshore.
Most landfalling tropical cyclones pose the threat for tornadoes because they create a change in wind direction by height. It’s in the northeastern quadrant of the storm where there’s that greatest risk because winds will be coming out of the southeast at the surface, but more out of the south or southeast in the mid-levels of the atmosphere. It’s definitely not a perfect setup for tornadoes, but short-lived ones with little warning often accompany storms like Alberto.
The last risk with Alberto is rough surf. Hazardous surf conditions are likely to develop along much of the central and eastern Gulf Coast through the holiday weekend. An onshore flow will bring days of rip currents to the Gulf Coast and even the Atlantic beaches of the Southeast. The strong winds will allow create swells that are likely to cause life-threatening surf and rip current conditions. It is best to stay out of the ocean now through at least early next week.