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Another Above-Average Hurricane Season Predicted

This is the time of year when meteorologists start predicting how many hurricanes we will experience in the Atlantic Basin. Frank Billingsley at Click2Houston.com issued his prediction for an above-average hurricane season Friday. He also predicts that other meteorologists will predict the same. Here’s why.

Official Averages Out of Date

The official window used to calculate the average number of storms has been 1981 to 2010. But when Brian McNoldy of the University of Miami looked at the more recent 30 years from 1991 to 2020, he found an increase in the number of storms. Also, AccuWeather has already come out with its prediction, showing a substantial increase.

Year(s)StormsHurricanesMajor Hurricanes
1981-2010 (Old Average)1263
1991-2020 (New Average)1473
2020 Actual30136
2021 Predicted by AccuWeather16 to 207 to 103 to 5
Sources: Brian McNoldy, AccuWeather, NHC

Other Contributing Factors

Sea-Surface Temperatures

Sea-surface temperatures are slightly above normal for this time of year. Despite the polar outbreak in February which cooled the Gulf somewhat, the Caribbean and Atlantic remain higher than average. See anomaly map below from NOAA’s Climate Prediction Center.

Seven day average as of 4/3/2021
La Niña

Billingsley’s prediction also takes into account La Niña, which is part of ENSO (El Niño Southern Oscillation).

NOAA describes El Niño and La Niña as the warm and cool phases of a recurring climate pattern across the tropical Pacific. The pattern can shift back and forth irregularly every two to seven years, and each phase triggers predictable disruptions of temperature, precipitation and winds.

The El Niño phase usually means fewer hurricanes in the Atlantic.

Typical influence of El Niño on Pacific and Atlantic seasonal hurricane activity. Map by NOAA Climate.gov, based on originals by Gerry Bell.

The La Niña phase usually means more hurricanes in The Atlantic.

Typical influence of La Niña on Pacific and Atlantic seasonal hurricane activity. Map by NOAA Climate.gov, based on originals by Gerry Bell.

Why? In short, the warm, wet air of El Niño in the tropical Pacific produces stronger vertical wind sheer which discourages hurricane formation in the Atlantic. The cool, dry air of La Niña produces less wind sheer which lets hurricanes form more easily.

National Hurricane Center

The real question is: How long will La Niña last? La Niña was strong last year. That meant one of the busiest hurricane seasons ever. (See table above.) But will it fade by the start of this hurricane season or the end? The Texas Water Development Board predicted it would begin to fade after this month. But some models show it lasting through the end of the year.

Bermuda High

AccuWeather predicts three to five hurricanes will make a direct hit on the United States this year. That’s partially due to another factor – the position of the Bermuda High. A weak Bermuda High means storms forming in the Atlantic would most likely aim at the Eastern Seaboard as opposed to coming into the Gulf.

Bottom line, “Be prepared. Anyone who has been through a hurricane can tell you it only takes one.”

Frank Billingsley, Click2Houston.com

Valuable Resources During Hurricane Season

For the full AccuWeather forecast, click here.

Colorado State University’s hurricane forecast comes out next week. It’s one of the most respected in the world.

During the season, the National Hurricane Center provides the most frequent updates of storm activities. They will start issuing tropical updates on May 15. And their reports will have more features than ever this year. See the list of new features including storm surge inundation values, weather forecasts for “blue-water” mariners, wave heights, cumulative maximum winds over 5-days, and more.

Posted by Bob Rehak on 4/3/2021 based on information from Click2Houston, AccuWeather, and NOAA

1313 days since Hurricane Harvey

“Above-Average” Hurricane Season Predicted This Year

USA Today has reported that hurricane experts from Colorado State University (CSU) have predicted an above-average hurricane season this year. How much above average? About 140%, they say. In addition, CSU predicts a 69% chance for a MAJOR hurricane (Cat 3, 4 or 5) to strike the mainland U.S.

Warm Atlantic and El Niño Seen as Main Factors

Reasons: unusually warm seawater in the Atlantic and the likely LACK of an El Niño in the Pacific. El Niño in the Pacific usually sets up wind shear that tears apart storms in the Atlantic. Said another way, they help keep tropical storms from developing into full-force hurricanes. But without El Niño, the lack of shear allows more storms to develop and creates active hurricane seasons.

Source: NOAA, From April 2, 2020. Shows most of Atlantic has above-normal sea-surface temps, and that temps immediately offshore the upper Texas and Louisiana Coasts are now 4-5 degrees above normal.

CSU predicts 18 named storms will develop.

AccuWeather released its hurricane season predictions a week earlier. They predict 14-18 names storms. Of those, seven to nine will likely become hurricanes, and two to four are likely to hit the U.S. mainland.

NOAA should issue its forecast in late May.

Hurricane season extends from June 1 to November 30.

March Warmth Unrelated to Hurricane Season

Jeff Lindner, Harris County Flood Control’s meteorologist, says that the unusually warm March that south Texas just experienced (about 8 degrees above normal) will have little effect on tropical storm formation. “There is some correlation with a warm Gulf of Mexico and severe weather and flooding along the Gulf Coast during the spring months. But there is little to no correlation to tropical activity in the Gulf during summer months.”

3-4 Inches of Rain Possible in Next 5 Days

Speaking of Spring rains, Lindner also predicts a stormy weather pattern will set up over our area for the next 5-7 days. He says “some severe weather and heavy rainfall will be possible.”

“Widespread rainfall amounts of 1-2 inches with isolated totals of 3-4 inches will be possible between this afternoon and Saturday,” says Lindner. He predicts the heaviest rainfall across area north of I-10. Storms could train, producing the higher rainfall amounts. But Lindner also adds, “It has been dry of late and the soil can take several inches of rainfall as long as it is not all at once.” So no one is talking about flooding at this point.

NOAA predicts a slight chance of severe storms Friday evening, mostly west of Houston.

Here’s where NOAA predicts the heaviest rains to fall during the next 5 days and what the total accumulations should be.

Posted by Bob Rehak on 4/2/2020

947 Days since Hurricane Harvey