FLORIDA HURRICANE FORECAST: With Fay away, all is calm – for now | WeatherTiger
On average, the third week of July is the hottest week of the year in much of Florida. This is a distinction without meaning in a state where June through early September are equally miserable, but perhaps it is some comfort to know that suffering ahead roughly equals suffering behind (from a temperature perspective).
Superfans of metric time and failed “Jeopardy!” contestants may recall the French Revolutionary calendar rebranded late July and early August as Thermidor, or literally “hot month.” Those seeking historical precedent should note that a hurricane struck New Jersey and New England in August 1789. This storm was likely set to a lyrically playful hip-hopera soundtrack, as was the fashion of the time.
Northeast U.S. landfalls are running ahead of schedule in 2020, as Tropical Storm Fay put its makeup on, fixed its hair up pretty, and came ashore last Friday in Atlantic City. Direct strikes on New Jersey are quite rare; Fay was just the second tropical system to make initial landfall there since 1851, though Hurricanes Irene and Sandy affected the Garden State in 2011 and 2012.
While Fay’s impacts on the Northeast were not severe, gale-force winds on the mid-Atlantic shoreline did bring some coastal flooding.
Today, the Atlantic remains quiet, with no organized tropical systems.
The only disturbed weather of note is a high-amplitude tropical wave in the far eastern Atlantic, just south of the Cape Verde islands. This wave would have a decent chance at developing without an outbreak of dry, dusty air just to its north, but instead has only the slimmest chances of brief organization as it moves west across the tropical Atlantic for the next week.
This wave again repeats the pattern of August-style growlers fizzling quickly over the eastern Atlantic. A lack of Main Development Region activity is not unusual, as a July storm forms there about once every six years, mostly in the second half of the month. Rather, this July is an odd juxtaposition of some environmental conditions that are favorable for development, and some that are highly unfavorable.
On the supportive side of the ledger, sea surface temperatures (SSTs) remain 0.5 to 1.5 degrees C above normal from west Africa all the way into the Gulf of Mexico. Low-level trade winds are lighter than normal: this both favors continued anomalous warming of the tropical Atlantic through August and September, and reduces unfavorable wind shear.
Finally, a developing La Nina is causing persistent rising air over east Africa, generating a Typhoon Lagoon wave pool of robust west-moving disturbances.
But just as you can’t bake cake just by putting flour and an uncracked egg in a hot oven, the Atlantic is missing two key ingredients for storm development: moisture and instability. Repeated, intense Saharan Air Layer outbreaks have flooded the Atlantic with air that is both less humid at the surface and warmer than normal aloft.
The result is that even big tropical waves are going poof when they move into open ocean.
Poor conditions are not unusual in July, but it is strange to have strongly favorable SSTs and low-level winds and strongly unfavorable thermodynamics cohabitating. Ultimately, SST patterns typically drive the bus in the peak season, and the next two weeks of trade winds only look to reinforce existing oceanic warmth.
Expect poor moisture and instability conditions to fold by early August, when those parameters climatologically trend more supportive for storm formation. Some model ensemble members are hinting at a chance of development down the road for waves emerging from Africa in three to four days and in six to eight days. Models have been too aggressive so far, but organization of the second tropical wave in particular would not be surprising.
There are three kinds of Florida summer weather: hot and wet, even hotter and less wet, and a third kind. You don’t want the third kind, and for the time being, there’s none in the forecast.
However, given July’s leading indicators of unusually warm SSTs and low shear, that might well change before the metric clock strikes 10 on this Thermidor. Keep watching the skies.
Dr. Ryan Truchelut, a failed "Jeopardy!" contestant, is co-founder and chief meteorologist at WeatherTiger, a Tallahassee start-up providing businesses advanced weather and climate analytics, forensic meteorology and expert witness services, and agricultural and hurricane forecasting solutions. Get in touch at firstname.lastname@example.org.