Atlantic hurricane forecasts for the coming weeks revised — and not in a good way
NOAA predicts up to 25 storms, with at least 3 major hurricanes
Already smashing records, this year's hyperactive Atlantic hurricane season is about to get even nastier, forecasters predict. In the coming months, they expect to run out of traditional hurricane names and see about twice as much storm activity as in a normal year.
The National Oceanic and Atmospheric Administration on Thursday upped its seasonal forecast, now predicting a far-above-average 19 to 25 named storms — seven to 11 expected to become hurricanes and three to six of those to become major hurricanes with winds of at least 175 km/h.
That's a few more storms than the agency's May forecast. It also increased the chance of an above-average hurricane season from 60 per cent to 85 per cent.
"It looks like this season could be one of the more active in the historical record," but it's unlikely to beat 2005's 28 named storms because the oceans were warmer and other conditions were more conducive to storm formation 15 years ago, said NOAA lead forecaster Gerry Bell.
This year's forecast of up to 25 is the highest number the NOAA has ever predicted, beating the 21 predicted for 2005, Bell said.
Colorado State University, which pioneered hurricane season forecasts decades ago, on Wednesday amped its forecast to 24 named storms, with 12 expected to become hurricanes and five of those becoming major hurricanes — all higher than its June forecast.
An average year, based on data from 1981 to 2010, has 12 named storms, with six hurricanes and three major hurricanes.
Lead Colorado State forecaster Phil Klotzbach said all the factors that cause hurricane seasons to be busy are dialled up this year, including increased storminess in Africa that seeds the biggest hurricanes, warmer water that fuels storms and reduced high-level winds that kill storms .
"Everything looks ready to be a pretty huge year," said University of Miami hurricane researcher Brian McNoldy, noting it's likely that there will be more storms than names. There are 21 names assigned to a hurricane season. If there are more than 21 storms, meteorologists turn after Wilfred to the Greek alphabet — Alpha, Beta, Gamma and so on.
In a normal year, about 90 per cent of storm activity comes after Aug. 6, with mid-August to mid-October as peak season. So far this year, there have been nine named storms, with most setting a record for being early. The most destructive so far has been this month's Hurricane Isaias, which killed at least nine people and left millions without power.
"Nine storms to this date is crazy," Klotzbach said.
Since 1995, when the Atlantic started a more active period for hurricanes, the average season has seen 12 named storms forming after Aug. 5, he said.
The number of storms doesn't matter as much as where they go, Massachusetts Institute of Technology meteorology professor Kerry Emanuel said, noting the busy 2010 hurricane season barely touched the United States.
Pacific storm season expected to be quiet
While the predictions are about the number of storms and not where they will strike, Klotzbach's forecast says the more storms there are, the greater the chances of U.S. landfall. It says there's a 74 per cent chance that yet another storm will hit the U.S. coastline somewhere, with a 49 per cent chance of a hit on the East Coast and Florida peninsula and a 48 per cent chance of a hit on the Gulf Coast.
Most of this year's storms so far have been weak, decapitated by high-level winds and dry air, but Klotzbach said that's about to change.
Sea surface temperatures in the eastern Atlantic are nearly 1 C warmer than normal. That not only provides more fuel for storms but changes air pressure and winds to make favourable conditions for storms to form and strengthen, he said.
Emanuel of MIT pointed to an extra quiet Pacific storm season as another indicator for an active Atlantic. When the Pacific is quiet, the Atlantic tends to be much busier, as they tend to balance each other out.
At the same time, water temperatures near the equator in the Pacific are cooling, with a brewing La Nina, which is the flip side of El Nino. Research shows there are usually more Atlantic storms during a La Nina.
Even though studies predict that a warmer world means generally stronger and wetter hurricanes, Emanuel and the NOAA's Bell said there are so many complicated factors in an individual season that they can't say either way whether man-made climate change is a factor in active years like 2020.
Bell said the biggest climatic factor "that dominates the hurricane trend" is a 25-to-40-year natural cycle of busy and weak hurricanes connected to large-scale Atlantic ocean and air patterns. The current active cycle started in 1995 "and we don't know how long it's going to last," he said.