Researchers at highly respected Colorado State University (CSU) issued their hurricane season forecast for 2021 last week. Like the University of Miami, AccuWeather and others, they predicted an above-average season based on sea-surface temperatures, the presence of La Niña, and historical analogs. CSU used data and models going back 40 years. Factors considered also include: where sea surface temperatures are warmer/cooler, sea level pressures, vertical wind shear levels (the change in wind direction and speed with height in the atmosphere), accumulated tropical cyclone energy, and more.
CSU Forecast Compared to Others
Here’s how CSU’s hurricane season forecast looks compared to historical averages and other predictions.
|1981-2010 (Old Average)||12||6||3|
|1991-2020 (New Average)||14||7||3|
|2021 Predicted by AccuWeather||16 to 20||7 to 10||3 to 5|
|2021 Predicted by Colorado State||17||8||4|
Striking Recent Parallels
According to CSU, so far, the 2021 hurricane season is exhibiting characteristics similar to 1996, 2001, 2008, 2011 and 2017. “All of our analog seasons had above-average Atlantic hurricane activity, with 1996 and 2017 being extremely active seasons,” said Phil Klotzbach, research scientist in the Department of Atmospheric Science and lead author of the CSU report.
In case you’re new to the Houston area and the significance of those bold-faced years escapes you:
- 2001 was Tropical Storm Allison which dumped 38 inches of rain on Houston, so much that it caused flood maps to be redrawn. The storm meandered over Houston for 4 days due to slow movement and weak steering currents.
- 2008 was Hurricane Ike which destroyed tens of thousands of homes on the Bolivar Peninsula. It killed 195 people, came ashore as a Cat 4 storm with winds of 148 miles per hour, came straight up Galveston Bay, went right over Kingwood, and knocked down so many trees that the Lake Houston Area lost power for 3 weeks. It did $38 billion in damage and ranks as the sixth costliest storm in US history.
- 2017 was Hurricane Harvey. HCFCD’s report on the storm says it all. At the peak of Harvey, five times more water went over the Lake Houston Dam than goes over Niagra Falls on average.
But 2011 was the opposite end of the spectrum. It was the driest year ever for Texas and the start of a drought that lasted through 2014.
Playing the Percentages
The CSU team predicts that 2021 hurricane season activity will be about 140 percent of the average season. By comparison, 2020 was about 170 percent. The 2020 hurricane season had six landfalling continental US hurricanes, including Category 4 Hurricane Laura which battered southwestern Louisiana.
The report also includes the probability of major hurricanes making landfall:
- 69% for the entire U.S. coastline (average for the last century is 52%)
- 45% for the U.S. East Coast including the Florida peninsula (average for the last century is 31%)
- 44% for the Gulf Coast from the Florida panhandle westward to Brownsville (average for the last century is 30%)
- 58% for the Caribbean (average for the last century is 42%)
Keep your fingers crossed and make sure you’re prepared. It only takes one storm to make your life miserable if you are not prepared. And remember, Allison happened on June 4th…just three days after the start of hurricane season.
Posted by Bob Rehak on 4/10/2021 based on a report by Colorado State University
1320 Days since Hurricane Harvey