Hurricane Michael moving into the Gulf of Mexico. Source: NHC
Hurricane season goes through the end of November, and with good reason. While we’re coming down off the peak there’s still quite a bit of time on the warm water clock of the Atlantic. As we head deeper into October, attention typically turns to the Gulf of Mexico and Caribbean as hot spots and that’s exactly where we find Hurricane Michael.
Current sea-surface temperatures in the Gulf of Mexico
The storm will be traversing very warm water over Tuesday and Wednesday leading up to landfall. And while some westerly wind shear may try to hold the storm somewhat in check, there’s a good chance of intensification as it heads toward the Florida panhandle. It will likely come ashore Wednesday near Panama City as a potent hurricane with damaging winds, heavy rainfall, and the always very dangerous storm surge.
What does it mean for us down the road? Rain, at the least. Michael will take a path into the southeastern U.S. and across the Carolinas before entering back out over the open ocean waters. At that point it will be moving pretty rapidly, but that doesn’t mean it can’t bring heavy rainfall to us here in New England. This type of setup often helps channel tropical moisture and that’s what I expect with Michael.
Animation showing the unusually high moisture content of the air over the next several days in the east. Source: Weathermodels.com
What we have for atmospheric players is the tropical cyclone, a cold front heading east, and a strong shortwave disturbance that will be diving down out of Canada. All this is happening underneath a huge ridge of tropical air in the east, so there’s no shortage of moisture. With Michael’s plume of tropical air getting sucked into this already anomalously humid air mass, there’s the risk of very heavy rain.
A jet streak at 250mb will be in the perfect position to enhance lift and produce a region of heavy rainfall as the tropical moisture moves north
These are pieces that sometimes produce a ‘PRE’ or predecessor rain event. A ribbon of heavy flooding rain that forms out in advance of a storm before the storm itself swings in. This isn’t a classic one since it currently looks unlikely that the storm itself will come up over the top of us on Friday. But it’s a similar idea. We have a jet streak overhead enhancing lift in the atmosphere. We have a front to focus the tropical moisture along a particular area. And we have an anomalously tropical air mass. These three ingredients will help produce some 3″+ rain totals. The question is exactly where those set up.
As of this writing on Monday, I’d say odds of 1-3″ of rainfall across our area is a good bet with the steadiest falling late Thursday into Friday morning. If all the ingredients come together perfectly over us, then we could see some 3″+ totals. We probably won’t know for sure where that ribbon of heaviest rain will be until Tuesday night or Wednesday…so expect some fine-tuning as we get closer.
The strongest winds of the storm are currently expected to stay offshore. But a little tick north and we could potentially bring tropical storm force winds into the Cape/Islands on Friday. We’ll need to keep a close eye on any trends in that direction over the next couple of days. The motion of the storm would keep the strongest winds overall on the eastern side of the circulation so that also helps limit our wind risk. If the incoming shortwave blows in quick enough the storm may pass out to sea on Friday with no further problems at all. Nevertheless, we have fully leafed out trees and it doesn’t take too much to cause issues.
Current probability of tropical storm force winds, per the National Hurricane Center on Monday