A couple weeks ago, it was 4 days of rain and gusty wind from Francine. This week, the remnants of Major Hurricane Helene will bring additional rain to the Mid-South. Well… partially from Helene.
Helene will be getting all the attention in weather-casts for the next couple days, and for good reason! Currently a Category 1 storm north of Cancun, Helene is forecast to traverse a very warm Gulf of Mexico under nearly ideal atmospheric conditions and explode to a category 4 storm by tomorrow afternoon before smashing into the Florida coastline in the Big Bend area near Tallahassee Thursday evening. Forecasters at the National Hurricane Center are warning of dire circumstances for the Big Bend region as life-threatening storm surge of up to 20 feet combines with hurricane-force wind of over 100 mph and flooding rainfall to create a miserable scenario, one that residents are being urged to evacuate from.
And the impacts don’t stop at the coast. Due to it’s level 4 intensity at landfall and quick forward speed, Helene will likely still be a hurricane well into southern Georgia and remain classified as a tropical storm as it nears Nashville on Friday afternoon! Along the way, strong wind gusts and copious rainfall will likely lead to widespread power loss, downed trees, and flash, urban, and river flooding over large areas. In fact, the southern Appalachians, particularly western North and South Carolina into northern Georgia, could see exorbitant rainfall amounts of 12-18″ in some spots, which the National Weather Service describes as such: “Extreme rainfall rates (i.e., torrential downpour) across the mountainous terrain of the southern Appalachians will likely inundate communities in its path with flash floods, landslides, and cause extensive river and stream flooding.”
So what about locally? Helene’s motion after reaching the Tennessee Valley slows down considerably and basically stalls/washes out this weekend near the confluence of the Ohio and Mississippi River to our north. It’s path will be directed by a strong upper level low pressure that will drop over the Mid-South on Thursday, causing the remnant low pressure of Helene to rotate around the Mid-South upper level low, finally coalescing into a single large low pressure system. This “dance” of the two lows whirling around each other is called the “Fujiwahra effect” and is more common in the Pacific Ocean when two tropical systems in close proximity have a similar effect on one another.
The fact that the two systems interact and ultimately combine means elevated rain chances for us, primarily driven by the pre-existing upper low, but enhanced by Helene primarily due to the influx of tropical moisture it brings. Rain will arrive in the Mid-South Thursday night from the east and largely remain in place for much of Friday. As the lows combine and Helene weakens a great deal, we’ll be left with scattered showers Friday night and into Saturday, ultimately dwindling by Saturday night as the resultant low pressure center starts to push off to our east.
Rainfall totals of 2-3″ will be possible especially for the northern half of the metro, from Thursday night through Saturday morning. In addition, wind will be somewhat gusty (to 25-30 mph) on Friday as the influence of Helene brings stronger wind. Thankfully, this should not necessarily result in a lot of power outages. But plan ahead for those Friday activities as rain could fall much of the day – and also keep temperatures in the mid 60s all day long!
Erik Proseus
MWN Meteorologist
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