After a record-setting onslaught of early season tropical storms in the North Atlantic (9 storms have been named to date), following a brief pause due to a monolithic hurricane-suppressing Saharan dust storm in late June, and then the recent Hurricane Isaias, which hove swell and havoc at the northeastern US, hurricane season looks to be on pause for now. But probably not for long.
Last week, NOAA issued a press release predicting an "extremely active" hurricane season for the Atlantic Basin. According to recent NOAA models, sub-season forecasts look to be pretty tame through the next week or so. Beyond that, though, NOAA's lead seasonal hurricane forecaster, Gerry Bell, Ph.D., says "This year, we expect more, stronger, and longer-lived storms than average, and our predicted ACE [(Accumulated Cyclone Energy)] range extends well above NOAA's threshold for an extremely active season."
"This is one of the most active seasonal forecasts that NOAA has produced in its 22-year history of hurricane outlooks," U.S. Secretary of Commerce Wilbur Ross said in a briefing.
According to NOAA's Accumulated Cyclone Energy (ACE) index, which is a measurement of the combined intensity and duration of all named storms during a given season by NOAA's Climate Prediction Center, we're looking at an 85 percent chance of an above-normal Atlantic hurricane season, with only a 10 percent chance of a near-normal season and a 5. percent chance of a below-normal season.
What's the cause? "Warmer-than-average sea surface temperatures in the tropical Atlantic Ocean and the Caribbean Sea, reduced vertical wind shear, weaker tropical Atlantic trade winds and an enhanced west African monsoon," NOAA writes.
That press release also discussed the possibility of a La Nina developing in the months ahead. That would mean cooler-than-average sea surface temperatures in the equatorial eastern Pacific (i.e., the west coast of the Americas), which would further weaken the hurricane-buffering vertical wind shear along the Atlantic basin. A wind shear, or wind gradient, is a difference in wind direction and works to shield tropical storms from developing and intensifying along the Atlantic seaboard of the US.
In effect, it is not two, three, or even four, but five converging factors that are opening up the floodgates to burgeoning tropical storms this season. And in all, the NOAA estimate is that we'll see somewhere between 19 and 25 named storms this season. Considering that hurricane season in the North Atlantic runs from June 1 to November 30, and that we're not even halfway through with 9 named storms to date, it's not hard to fathom. The metamessage from NOAA? Be prepared.
Let's just hope this seaboard and nation, already reeling from the effects of one natural disaster in the form of a pandemic, can gear up in the way of preparedness for another.