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September is Peak Hurricane Season for the United States

By Tom Ross

picture is worth a thousand words and the graphic shown in this month’s article depicts the historical frequency distribution of hurricanes and tropical storms for the last 100 years according to NOAA.

The official hurricane season for the Atlantic Basin (the Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico) is from 1 June to 30 November. As seen in the graph, the peak of the season is from mid-August to late October, with the highest number of storms occurring around September 10. However, deadly hurricanes can occur anytime in the hurricane season. As mentioned last month, it’s not how many storms you have but how many make landfall in the U.S. that counts. Nevertheless, the graph points out that we are in the midst of the Hurricane season, and it is best to keep track of all these storms. NOAA’s National Hurricane Center is the organization responsible for keeping us all informed and can be found at nhc.noaa.gov.

What a Difference a Year Makes

Turning to our current weather and climate across the region, what a difference a year makes. Last year in late summer we could not buy rain and were in the midst of a drought. Remember our brown yards and crunchy grass because of the lack of rain? Well, that pattern has certainly turned around. I can actually say that the slogan “Cool, Green Asheville” has had more truth this year than last, and we are heading into the fall with a precipitation surplus, not anything like what we had to deal with last year.

Another feature of September weather is the “end” of the summer. Actually, meteorological summer — which is defined by the three warmest months of the year, June, July and August, has already ended. The amount of solar radiation, hence the length of day, starts out at 12 hours 54 minutes on the first of the month and is down to 11 hours 50 minutes by month’s end — a decrease of an hour or so of daylight. The temperatures also show a marked decrease as well and follow the trend of decrease heating; normal high and low temperatures start out at 80 F for a high and 60 F for a low and drop almost 10 degrees on average, to 72 F for a high and 50 for a low by month’s end.

On a forecast note, we have enjoyed quite a few cool spells this summer thanks to cooler air or a trough in the eastern half of the U.S. making inroads over part of the Carolinas from time to time. In contrast, the western states were quite hot this summer because of an upper level ridge over portions of the Rockies and the Southwest a good part of the summer. If this pattern holds, with a trough in the east and a ridge in the west, it could lead to a colder fall and winter — or at least portions of those seasons — but we may be getting ahead of ourselves at this point. More on the winter outlook in the October and November reports.

August Trivia Answer

What is the main instrument used by Hurricane Hunters to collect data?

During flight, weather data is continuously collected and sent to the National Hurricane Center via satellite. While penetrating the eyewall, a weather instrument called a dropsonde is released to determine maximum winds at the surface, and another “sonde” is released in the eye to detect the lowest pressure at the surface. This instrument gathers data including wind direction and speed, pressure, temperature, and humidity from the plane’s altitude to the water’s surface, creating a vertical profile of the atmosphere. After exiting the eye, the a vortex message — including latitude and longitude of the center as well as maximum winds, maximum temperature, and minimum pressure — is created.

Meteorologist Tom Ross managed the Climate Database Modernization Program at the National Climatic Data Center.