Less than 36 hours remain before the first rain bands from Michael spin ashore the Florida panhandle. Just three days ago Michael was a non-threatening cluster of thunderstorms fed through the rainforests of Central America. Now Michael is a massive and intensifying Category 1 hurricane barreling toward the Gulf Coast. The storm’s dramatic intensification has left the Gulf Coast scrambling to make preparations ahead of a direct landfall from what could soon be a major hurricane.
Michael was an 80 mph Category 1 hurricane with minimum central pressure of 978 mbas of 5pm EDT October 8. The hurricane was located 30 mi northwest of the western tip of Cuba and was heading northward at 9 mph. Incredibly, Michael’s growth occurred under the influence of modest wind shear. Wind shear is expected to lessen as Michael continues northward into the bathtub-like waters of the Gulf of Mexico, permitting Michael to undergo a period of rapid intensification ahead of landfall.
A deep-layered trough currently bringing torrential rain to the Central US will creep eastward over the next few days, pushing Michael to the northeast toward Panama City. Almost all of the most commonly referenced ensembles and deterministic models print a track clustered in the western half of the Florida panhandle, with landfall between late Wednesday morning and late Wednesday afternoon. Intensity is the only significant remaining source of uncertainty.
A significant spread in intensity still exists among most NWP models. The graphic below from NOAA’s Environmental Modeling Center illustrates this fact for just a handful of American models. The 12 UTC GFS (AVNO) only intensifies the storm’s maximum sustained winds to strong Category 1 intensity whereas the HWRF intensifies Michael to nearly Category 4 hurricane status. Oddly, the GFS also deepen’s Michael’s central pressure to sub-960 mb levels, which is more indicative of a Category 3 hurricne. The wind intensity differences highlight the modeled differences in the size of Michael’s wind field. Conservation of angular momentum requires wind speeds to be smaller as the radius of circulation expands. It should be noted that the HWRF was the first deterministic model to suggest the possibility of Michael becoming a major hurricane and thus far, has the smallest absolute errors in intensity and track of the models in the graphic below. The true model intensity will likely fall between these two extremes, but favor the stronger range of guidance based on Michael’s dramatic evolution thus far. Michael is therefore expected to be a modest Category 3 hurricane at landfall.
Conditions will rapidly begin deteriorating along the Gulf Coast Tuesday afternoon into evening, when winds will gradually intensify. The fetch created by Michael’s wind field will generate an increasingly more intense storm surge between Tampa and Biloxi Tuesday through Wednesday night. Inundation will range from 2-4 feet along Tampa Bay and the central Gulf Coast to an island-swallowing 8-12 feet along the eastern Florida panhandle. Storm surge will peak Wednesday morning just ahead of Michael’s landfall. Residents of coastal Florida from Panama City to Cedar Key should expect their neighborhoods to be completely submerged by the rising storm surge.
Scattered downpours will reach Tampa by Tuesday afternoon and Panama City by Tuesday evening. The downpours will increase in coverage and intensity overnight Tuesday into Wednesday from Pensacola to Tallahassee, Wednesday night into Thursday from Albany to Atlanta, and Thursday into Thursday night in the Carolinas. Meanwhile, Michael’s feeder bands will continue to bring scattered downpours to the western Florida peninsula through Thursday.
A sharp gradient in precipitation will exist to the west of the storm’s eye such that downpours in Mississippi and western Alabama will be low in coverage. The heaviest rain will fall along Florida’s western panhandle northeastward through central Georgia Wednesday and in central South Carolina Thursday. Up to 16″ of rain could fall near the vicinity of Michael’s landfall in western Florida, with 6-12″ of rain likely elsewhere in this bulls eye. An additional bulls eye of rainfall will straddle the Tennessee/North Carolina border as winds circulating counter-clockwise flow up the Blue Ridge mountains. These torrential tropical rains will instigate flooding over the same areas still recovering from Hurricane Florence, which made landfall less than one month ago.
Wind gusts will likely exceed 100 mph within a few dozen miles of Michael’s eye along the western Florida Panhandle. Tropical-storm force winds could extend over 200 mi from Michael’s center of circulation. Tampa, Mobile, and even Atlanta could experience Tropical Storm Force winds, despite the latter being roughly 200 mi from the coast. Michael will accelerate so fast that it will still maintain tropical characteristics as it plows across the Southeast. Millions across the region will undoubtedly lose power. Roads will become impassible due to flooding, debris, and fallen trees and power lines. Roofs will be torn from their structures near the eye of the storm. Some buildings may suffer so much structural damage that collapse may be inevitable. Fortunately, the quick progression of Michael will limit the extent of wind damage to such a severe extent.
Michael will gradually interact with the jet stream and nearby frontal systems throughout the week, becoming extra-tropical in the process. Undead Michael will re-intensify once ejecting the Mid-Atlantic coast Thursday night, possibly bringing powerful Nor’Easter like conditions to the Delmarva, New Jersey and Long Island Thursday night and Friday. Michael’s track is still uncertain at this point, so more will be discussed about impacts to the Northeast later this week.
Michael is already a life-threatening storm and is becoming more dangerous with each passing hour. Time is dwindling to make preparations before Wednesday’s landfall. Be sure to have plenty of water, non-perishable food items, batteries, and other emergency supplies, enough to last for at least one week without power, or at least two weeks near the vicinity of forecast landfall. Follow evacuation orders and other instructions from emergency management. Be sure to check back with WeatherOptics as we continue to provide updates on this upcoming disaster.