Have we seen this hurricane season before?

Flooding from Harvey. Image from click2houston.com
Flooding from Harvey. Image from click2houston.com

On Wednesday, I blogged about the newest hurricane forecast from Dr. Phil Klotzbach of Colorado State University. He is forecasting 17 storms of which eight become hurricanes and four become major (Cat. 3) hurricanes.

A lot of research goes into his prediction and, as I discussed, a couple of important factors are the state of La Niña/El Niño and the temperatures of the Atlantic Ocean waters. Specifically, presence of La Niña = a busy season, and warmer than normal sea surface temperatures = a busy season. We have both a weak La Niña and warm water, thus, his forecast of 17-8-4 is above the average season of 14-7-3.

In addition to the many parameters Dr. Klotzbach pores over, he also examines the historical climate record. What years in the past looked a lot like this year from a climate perspective and just what kind of tropical activity did THOSE years have? Perhaps something is to be gleaned from the past. In his tropical meteorology report, he says specifically:

“Certain years in the historical record have global oceanic and atmospheric trends which are similar to 2021. These years also provide useful clues as to likely levels of activity that the forthcoming 2021 hurricane season may bring. For this early April extended range forecast, we determine which of the prior years in our database have distinct trends in key environmental conditions which are similar to current February/March 2021 conditions and, more importantly, projected August–October 2021 conditions.”

So what years compare to this year? Here they are:

Those years look familiar...

The years above had similar climate states as we find today, and in those years, the storm count ranged from 13-19 with the hurricane count ranging from 7-10. Such comparison to 2021 gives rise to the 17-8 number from Colorado State.

So what?

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