Wind shear and Saharan dust could cause new turbulence in the Atlantic: John Morales
For the first time in three and a half weeks, the National Hurricane Center on Wednesday added a new system to monitor the Tropical Atlantic Main Development Region.
Since Tropical Storm Cindy dissipated on June 25, the MDR has remained quiet despite an overheated ocean. Outside the MDR, Tropical Storm Don made little headlines as it slowly meandered across the open ocean hundreds of miles west of the Azores.
Don is the fifth system to be classified as a tropical or subtropical storm in the Atlantic this year, notable in that the fifth storm does not usually appear until August 22.
The MDR continues to experience very high sea surface temperatures, averaging about one degree Fahrenheit above normal. In mid-June, this temperature anomaly was more than 2°F above average.
Thankfully, the unusual heat is no longer as extreme as it was just over a month ago. But it is still warm, and this continues to worry weather forecasters.
The lull observed in the MDR after Cindy was mainly due to stronger westerly winds in the upper levels. This wind shear, hostile to incipient tropical disturbances, is seen more frequently during El Niño years.
On June 8, the NOAA Climate Prediction Center officially announced that El Niño conditions are already in place and are expected to last until the end of the year.
The atmosphere is dynamic and wind shear will not be constant throughout the 2023 hurricane season. Forecast models indicate that these overhead westerly winds will ease next week, leaving room for a potential increase in the disturbance currently seen south of the Cape Verde Islands.
After months of gradual rise in sea surface temperatures in the tropical Pacific, NOAA officially issued an El Niño warning Thursday.
But there is another factor that can prevent the development of the disorder. The largest outbreak of Saharan dust this year today spans much of the tropical Atlantic from Africa to the Greater Antilles. The air layer of the Sahara is dry and stable, which is the opposite of what is needed for tropical disturbances to develop into tropical storms.
Depending on how closely the disorder interacts with dry air, it can impair its chances of developing.
For now, the NHC only gives the system a 20 percent chance of becoming a tropical cyclone over the next seven days.
Historically, the busiest part of the hurricane season is just around the corner. It will start in about four weeks. August 15 to October 15 is the time of year when we need to be on our toes when it comes to hurricane preparedness. The battle between hurricane-friendly hot seawater and hurricane-opposing wind shear will be played out at this site.
Keep in mind that while the MDR is cooling down a bit, the Gulf of Mexico is still as hot as it has been throughout the spring and summer compared to the norm. And the waters around Florida and the Caribbean are so hot that outbreaks of coral bleaching are already occurring — something that usually doesn’t happen in years when it happens through late summer and early fall.
Be strong, wind shear. We are all rooting for you.”
John Morales is a hurricane specialist for NBC6.
