Good afternoon Arkansas, hope you all are enjoying what the watcher ordered, wetter and cooler. Definitely a nice break from what we have had this sizzle summer. Well as promised from last week, we will dissect the pattern for the rest of “SUMMER”
Normally for August the three “Hs” come into play, Hazy, Hot, Humid. We have seen plenty of that this summer that started early and often. As we roll into the last half of August, we can forget those three words. First let’s start with the current setup that will affect us through Wednesday. As I write this, there is a low in Southwest Arkansas pumping continuous amounts of rainfall into the state. This same low is responsible for record breaking rainfall across the Gulf Coast. This low has been forced west by the Bermuda High to the east and the heat ridge to the west is now forcing it north. At the same time a stalled out cold front is supplying the lift needed for a long slow rain. This setup is normal for late April early May not mid-August, unless associated with a tropical storm. With the highs on either side of the state, there is not much steering in the atmosphere for the front or the low causing it to meander around. Given the amount of moisture in the atmosphere, almost 3 inches, which is nearly record levels for this time of year, heavy rain is unavoidable as well as flooding. The Bermuda high to the east will gradually break down and move south allowing the low to ride up the front to the Ohio Valley. With the front still around through mid-week, rain chances will continue and provide several inches of rain with these highs providing a plume of moisture. The good thing with this pattern is that the temps will be very low for August. Our normal high is about 94 degrees. Highs early week will be in the 70s and 80s under the rain and clouds
Now a lot of you have asked me recently about severe weather season and tropical outlooks and of course fall. With El Nino pretty much gone and La Nina weak this year, this could have adverse effects on our weather. As we head into the end of August and early September the normal pattern is a gradual decrease in temps and an uptick in rainfall and severe weather as well as tropical systems. This year looks to be different. We are currently in a fall like pattern as I write this and long range global models as well as atmospheric patterns, continue this into the fall. Will there be at least one more 90-degree day? Possibly. One thing no one can predict is how strong the highs will end up being. The Bermuda high tends to shift back out to sea and the western ridge back to northern Mexico. Some data indicates one last surge near the end of the month. Most indicate a continued fall like pattern with lower humidity. I do believe we will see a return of humidity and moisture by months’ end as well as into September. Early on we may see a few 90s but nothing like what we have had. 80s will be the norm from here on out as well as rainfall. After a top 15 wet spring, top 15 wet summer, I don’t see why that pattern will break now. The downfall with increased moisture and cold fronts moving through, is the increase in severe weather. September through Thanksgiving is our typical 2nd severe weather season. Some of our most prominent outbreaks have occurred in the fall and winter months. That being said, La Nina is known for active fall seasons. We are in a weak La Nina state so therefore our severe weather episodes could start early in the season. Based on my experience I will call it a slow uptick in severe weather due to the consistent cooler air working into the region, shunting Gulf Moisture south. Eventually the two will meet and the track of storm systems will eventually move from Texas to the Ohio Valley providing the ingredients for severe weather. I do not see this happening until later in the month and later in the fall.
The wrench in this idea will be any tropical development. La Nina will begin to make the shear in the Atlantic subside, providing the environment needed for development. As we head into the fall, tracks favor the Gulf Coast as well as Arkansas. The US has not had a major land falling hurricane in 10+ years and we are way overdue. Gulf waters are very warm for this time of year. These warm waters supply the fuel for tropical development. In the weak La Nina state we are in, the tropics will begin to pick up. Even the National Hurricane Center has increased their prediction on storms for the year. I fully agree with this decision. The next 6 to 8 weeks are the peak of the season. Will any of these tracks take them to the Natural State? History serves us with the answer that yes, it is very possible. When we get these systems, flooding rains and tornadoes are common. This would be the only reason that severe weather would start earlier. There is nothing on data right now that indicate this scenario, however that can change very rapidly this time of year. If the low this weekend had stayed in the GOM longer, then It would have been a tropical system. A lot of these details all depend on overall atmospheric patterns that will be ran by the Equatorial Pacific which is where El Nino and LA Nina originate.
Before I forget, for the kiddos first week of school, umbrellas and rain coats are a must. Highs in the 70s and 80s morning lows in the 60s and 70s. with rainfall all week. Hope all of the kids out there have a blessed first week of classes.
~Senior Forecaster Derek