1st Atlantic system poised to bring heavy rainfall to South Florida
After what feels like an uncharacteristically quiet May (after all, it has been since 2014 that we have gone this late in the year without a named Atlantic storm), the tropics are beginning to percolate.
On the eastern Pacific side, Hurricane Agatha made landfall on Monday in Mexico as a Category 2 storm, the strongest May storm to impact the Pacific coast of Mexico since recordkeeping began in 1949. It has since weakened to a tropical depression over southwestern Mexico but continues to produce torrential rainfall and flash flooding.
Our computer models are in good agreement with peeling off some of Agatha’s remnants this week as it tracks inland over Mexico and merging it with a broader area of storminess over the Gulf of Mexico or the western Caribbean by late Wednesday into Friday.
As of 8 a.m., Tuesday, the National Hurricane Center is giving this area a 60% chance of developing into our first Atlantic tropical depression or named storm by week’s end.
The area outlined by NHC is over a favored part of the Atlantic for storm formation in early June. Agatha isn’t expected to maintain its status as a tropical depression over the rugged terrain of Mexico, so if a tropical storm forms of its remnants in the Gulf this week, it would be christened Alex – the first named storm of the 2022 Atlantic Hurricane Season.
Throughout May the Atlantic has been under largely dry, sinking air. This is part of a larger disturbance in the upper atmosphere called the Madden-Julian Oscillation.
May isn’t exactly a favored time of year for tropical formation, but it’s especially not so under the influence of sinking air, which dries out the lower part of the atmosphere. The yin to the yang of this sinking air branch of the Madden-Julian Oscillation is the rising air branch, which has recently made its way into the eastern Pacific, Gulf of Mexico, and the Caribbean Sea. This change in the upper air wind configuration has prompted the pattern flip we’re currently seeing.
As the Madden Julian Oscillation progresses eastward into the Atlantic this week, it will help to reduce somewhat the typically hostile early June wind shear across the Gulf of Mexico, which will serve to promote storm organization. The Gulf is also notably warmer than average for late May; in fact, with the exception of 2015, over the past week, it’s been warmer than any similar period since 1981. So the Gulf “feels” more like mid-June than late May, which should provide some kindling for the brewing disturbance.
That said, a dip in the jet stream over the western Gulf this week should keep our system in check, and typical of early June, our models keep it a sloppy, lopsided system as it moves toward South Florida this weekend. It’s worth mentioning that none of our current guidance suggests development into a strong storm. The upshot for South Florida will be a surge in tropical moisture with the potential for heavy rainfall and flooding, especially after recent rains over the weekend. The timing of heavy rainfall will be Friday into Saturday for the WPLG viewing area.
A concern for southwestern Florida may be the possibility of some minor to moderate storm surges and coastal flooding, depending on the strength of the system. Models indicate the possibility of a hybrid (or subtropical) system, which, due to the broader extent of winds, would also increase the coastal flood threat to southwest Florida, even if the system remains weaker. This is something we’ll want to watch for our friends on the Gulf side as we progress through the week.
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