August begins on a drier note
By Skip Rigney
A weak cool front passed through on Wednesday, ushering in three days of lower humidities and slightly cooler mornings. The total water vapor in the lowest twelve miles of the atmosphere, as measured by weather balloons launched Thursday morning and evening by the National Weather Service in Slidell, was drier than 95 percent of early August observations for our region.
The much drier air brought a break from the daily showers and thunderstorms that have soaked Pearl River County this summer. Frequent rains during June and July have pushed rainfall totals so far in 2021 in the southern part of the county to near or above the 65-inch amount that is average for an entire year.
The northern part of the county has received less rain, but has still been significantly wetter-than-normal, accumulating 50 to 60 inches since January 1, 2021.
The rainier-than-average start to the year, and especially to the first two months of summer, has affected most areas within 100 to 250 miles of the coast across the southern states from Virginia all the way to south Texas.
That’s in marked contrast to the drought in the western United States. In regions that, even in normal years, are much drier than we are, the drought is fueling a historic wildland fire season. Already this summer 100 large fires have burned almost 2 million acres in 14 western states according to the National Interagency Fire Center, which is located in Boise, Idaho.
Back here at home, the post-frontal northerly winds that brought us drier air shifted back to southerly on Friday and are forecast to continue gently blowing onshore from the Gulf during the upcoming week.
That means a return of muggy humidity levels and, beginning today, a return of a chance of scattered mostly afternoon showers. With rain chances between 30 and 50 percent, any given location can expect rain one or two days out of every three.
With the approach of mid-August, an increase in the number and strength of tropical disturbances in the Atlantic, Caribbean, and Gulf is to be expected. This week two of the top organizations in the field of long-term seasonal hurricane prediction issued updates to their outlooks for 2021 tropical activity.
The National Oceanic and Atmospheric Administration’s Climate Prediction Center (NOAA CPC) estimates that there is a 65 percent chance that this season will be more active than average with 15 to 21 named storms (14 was the average for the last 30 years), 7 to 10 hurricanes (7 is the 30-year average), with 3 to 5 of those with winds above 110 miles per hour (3 is the 30-year average). NOAA CPC expects that lower wind shear, weaker trade winds, and a stronger than average West African Monsoon will continue the high-activity era that began in the Atlantic in 1995.
Colorado State University’s (CSU) Tropical Weather and Climate Research group nudged their estimate down just a little in the outlook they issued on Thursday compared to the forecasts they issued earlier this summer.
Based on observations from July of sea surface temperatures in the northeastern Atlantic, high level winds above tropical Africa, and the strength of the trade winds in the Caribbean Sea, Dr. Phil Klotzbach and his CSU collaborators now expect that this season will have slightly above-average activity.