A closer look at a rough hurricane season


With two historic hurricanes in the period of a couple of weeks, it's been a brutal time for folks across the southern United States. First Harvey, with its 130 mph winds and painfully slow progress, devastated Houston and Coastal Texas.

Harvey was the first major hurricane (Category 4) to hit the U.S. since Wilma in 2005. It was also the wettest storm on record in the contiguous United States. Hot on its heels came Irma, at one time a Category 5 hurricane with 185 mph winds. When it hit Florida over the weekend, it had "weakened" to a Category 4 storm with similar 130 mph winds. Its remnants are only now slowly moving off to the east, setting the stage for what should be a mostly sunny and warm weekend for us.

How did we have two such incredible storms back-to-back? Well, conditions were almost “perfect.” The storms took southern tracks that kept them over the warm waters from which they draw their strength. The air above was unusually moist, which also fueled the intensity of the rotating bands of thunderstorms that comprise a hurricane.

What’s more, there was no wind shear or other weather conditions that can cause these storms to weaken or fall apart. And, finally, it’s the middle of the Atlantic hurricane season, which runs from June to the end of November and tends, statistically, to peak around the second week of September. Still, it was the first time on record that two such storms have hit the United States in the same year, let alone back-to-back.

Next up is Tropical Storm Jose, which looks like it will strengthen back into a hurricane by the weekend, but the projected track keeps it from striking the southeast as it rides up along the east coast, generally well off shore.

An average hurricane season has 12 named storms., with a maximum of 21 pre-ordained names. (The letters Q, U, X, Y and Z are omitted). If there are more than 21 tropical storms in a season, they move on to the Greek alphabet. (Alpha, Beta, etc). Storms get their names when they become tropical storms, with sustained winds of 39 mph. So far we’ve already had 11 in 2017. Six of these became hurricanes, meaning sustained winds of 74 mph, and two of these were “Major hurricanes:” Harvey & Irma.

By the way, there’s a 6-year rotation of names in place for tropical storms and hurricanes and they do not come from NOAA’s National Hurricane Center. There’s a group called the World Meteorological Organization that compiles the list, which incorporates both male and female names. In the event of major damage, cost or loss of life, those names are then retired, never to be repeated. Harvey and Irma will be added to the list that already includes names like Andrew, Katrina, Sandy, Ike, Hugo and Fran, which I covered, along with the unretired Edouard, back in 1996. Here’s a link to the names you won’t see again.

Did forecasters see all this coming? As a matter of fact, they did. While seasonal hurricane forecasts are subject to revision, an update in early August projected 14-19 named storms, with 5-9 hurricanes and 2-5 major hurricanes. So we are on track so far. Hopefully the remainder of the season will not see a repeat of these. I've heard it asked whether storms like Harvey and Irma are a product of global warming. While there's still some debate over the impact of global warming when talking about specific severe weather events, there does seem to be a growing consensus that future storms may be "stronger and wetter."