Scattered showers continue this week; tropics more active
Published 7:00 am Tuesday, August 8, 2017
By Skip Rigney
It has rained in most locations in south Mississippi and southeast Louisiana almost every day since last Wednesday. Most of the showers and thunderstorms were of the typical summer variety, but a few produced torrential downpours.
Saturday afternoon a thunderstorm dumped one to three inches of rain over the southern third of Pearl River County in less than two hours.
But, that was a light shower compared to the deluge that hit New Orleans on Saturday afternoon. Friends of mine who decided to spend a cool afternoon at the Aquarium of the Americas in New Orleans found themselves stranded for several hours because of flooded streets.
Over seven inches fell in some New Orleans neighborhoods in just a few hours.
The rain poured down faster than the below-sea-level city’s pumping system could pump it out resulting in a number of businesses and homes being flooded.
The numerous showers we have seen since the middle of last week have been the result of very moist, unstable air and a trough of low pressure that has been stalled along the Gulf Coast.
These recent rains continue the wetter-than-average pattern that we have seen along the northern Gulf Coast since May. Most locations in Pearl River County have received between one and one-half to double the average amount of rain over the past three months.
National Weather Service forecasters predict that high pressure in the upper levels of the atmosphere above us will become a little stronger the rest of this week. The sinking motion associated with the upper high should result in a slight decrease in the number of showers and thunderstorms over the next few days. They also should be more restricted to the afternoon and early evening hours.
Still, it is likely your location will have several showers and thunderstorms over the next week.
Low temperatures will be in the middle 70s, which is a few degrees above average. Highs will be in the upper 80s, which is a few degrees cooler than average.
Tropical Storm Franklin formed in the northwest Caribbean Sea Sunday night. Fortunately for us, the Bermuda High Pressure Ridge extends into the central Gulf, blocking any northward movement of Franklin.
Franklin is expected to move westward across Mexico’s Yucatan Peninsula and into that region of the far southwestern Gulf known as the Bay of Campeche before moving onshore in Mexico.
Franklin likely will be followed by a number of other tropical storms and hurricanes over the next two months. Last week the long-range hurricane outlook experts Philip Klotzbach and Michael Bell of Colorado State University issued the early August update to their 2017 seasonal outlook.
They expect eight hurricanes during the remainder of 2017, which is slightly above the historical median of between five and six.
Their updated August outlook is two higher than the six hurricanes they expected when they put out their June outlook.
Klotzbach and Bell cite two main reasons for why they think 2017 will be a more active season. One is that the large-scale atmospheric and oceanic phenomenon known as El Nino is absent this summer. When an El Nino is underway there tends to be fewer hurricanes in the Atlantic. The other factor is that sea surface temperatures in the tropical and subtropical Atlantic are now warmer than average, which enhances tropical cyclone development and strength.