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First, there are the ongoing storms. Tropical Storm Nana struck Belize as a Category 1 hurricane around 2 a.m. Eastern time on Thursday with maximum sustained winds of 75 mph. Even as the winds quickly begin to subside, heavy rain could trigger flash flooding and mudslides inland across Belize, Guatemala and the Mexican state of Chiapas. The storm is predicted to weaken into a remnant low-pressure area on Friday.
Tropical depression Omar, meanwhile, is drifting aimlessly over the western Atlantic, clinging to life despite being located in a hostile environment with strong upper-level winds that are tearing apart some of its thunderstorms and preventing it from organizing further. The stubborn system has lasted longer than expected, and the National Hurricane Center wrote that Omar “refuses to give in.”
At the same time, three additional areas the Hurricane Center is watching are crowding the east tropical Atlantic. Two tropical waves are over the warm waters of the Atlantic in various stages of development. A third is still drifting over western Africa but could mature upon emerging overwater.
It has been an extremely busy hurricane season to date, with activity running about a third above average for this point in the season. Nana and Omar were the earliest N and O named storms on record, the latest dominoes to fall in a year that has also featured the earliest recorded C, E, F, G, H, I, J, K, L and M storms.
Barely halfway through hurricane season and with the season’s peak less than two weeks away, it’s probable we’ll exhaust the traditional list of hurricane names before long and be go to Greek letters.
Nana strikes Belize and moves inland
Tropical Storm Nana made landfall as a hurricane about 45 miles south of Belize City at 2 a.m. Eastern time as the first hurricane to make landfall in Belize since Hurricane Earl struck in 2016.
Now a tropical storm, Nana will continue to bring wind and rain to parts of Belize, Guatemala, and portions of southeastern Mexico. Localized rain totals of 8 to 12 inches could spark flooding.
Removed from its oceanic heat source and moving over hilly terrain, Nana is expected to become a remnant low on Friday. Infrared satellite imagery revealed thunderstorms blossoming even after Nana had moved inland Thursday morning, indicative of heavy rain falling.
Tropical Depression Omar
Tropical Storm Omar formed Tuesday morning over the open Atlantic, off the U.S. East Coast. It has since struggled to combat wind shear, or a change of wind speed and/or direction with height, that caused its thunderstorm activity to become detached from an exposed low-level center. The naked tropical cyclone had not succumbed to the shear as of Thursday morning, though it is expected to within the next 24 hours.
Three areas to watch in eastern Atlantic
Three tropical waves were swirling in the eastern Atlantic and poised to move off of western Africa as of Thursday morning. From west to east, the systems had a 40 percent, 70 percent and 20 percent chance of development, respectively, during the next five days.
The lead disturbance to the west, which was located midway between South America and Africa, was in no hurry to develop early Thursday. Instead, the tropical wave, which had a small number of showers and thunderstorms associated with it, will probably need help if it is to develop.
Computer models are struggling to simulate how the two tropical waves that have already exited the African coast may influence one another or interact. It is possible that one, both or none of them will develop into a named system.
Meanwhile, the third tropical wave — located inland over Nigeria, Chad, and Niger — appears innocuous right now. But things could change in a hurry late in the weekend as this area of showers and thunderstorms moves over the tropical east Atlantic.
Given the likelihood that conditions over the tropical Atlantic will be conducive to storm formation next week, it’s likely that we’ll see more named storms forming.
Concerns about U.S. impacts
While there are no systems of immediate concern for the Lower 48, there are signs that the upcoming weather pattern may put the United States at greater risk of a hurricane landfall than is typical.
We are into Cape Verde hurricane season, a name assigned to the part of the season when the eastern tropical Atlantic begins to awaken. Most monstrous hurricanes blossom there, maturing over the Atlantic’s Main Development Region — an imaginary rectangle of warm ocean waters where some of the most favorable air and ocean conditions overlap.
To what extent any systems that develop there are driven west, rather than curving harmlessly out to sea, hinges primarily on how strong the Bermuda High, or a semi-stationary zone of high pressure parked over the Atlantic, is.
Computer-model projections suggest that this high-pressure area may permit out to sea options for systems that develop through about Sept. 8 or 9, but thereafter — particularly toward the middle of the month — the Bermuda High could strengthen and build south and west.
That would increase the odds of any tropical systems affecting the East Coast or Southeast if any were to develop.
There is considerable uncertainty regarding the mid-September weather pattern, as it depends on factors as remote as the interaction between Pacific typhoons and the upper-level jet stream.
In any case, all signs point to more tropical storms and hurricanes forming in the tropical Atlantic during the next few weeks, and they will have to be watched warily.