August 31, 2011 Update

Early Taste of Fall: August 16, 2011

If you've stepped outside first thing in the morning the past two days, it has felt more like October than mid-August! Low temperatures have nestled into the middle and lower 60s across the Magnolia state and with lower humidity values, it has felt especially crisp in the morning and not as oppressive in the afternoons, even though we continue to top out in the mid 90s.

A "cold" front passage over the weekend brought us a few showers on Saturday afternoon, but more noticeably was the dry, continental air!

However, the pattern is beginning to transition back into one that is more characteristic of summertime in the Deep South. The relentless heat has returned to the southern Great Plains. Dallas, TX had an incredible 40 day streak of 100+ degree days, consecutively. With another expansive High Pressure center building over this area, the overall upper air pattern is becoming more amplified rather than zonal. For us in Mississippi, we are seeing a predominantly northwesterly flow aloft as we are on the eastern side of that heat ridge:

This type of weather pattern lends itself to upper level disturbances (MCS's) which ride the periphery of that heat ridge. At the time of writing, one of these disturbances is creating some showers and thunderstorms over central and southern Missouri, developing into northeast Arkansas. Over the past 2 days, these disturbances haven't made it this far south, but the "convective debris," (the high cirrus clouds) have filtered in, especially overnight and that has kept our temps from reaching the low 60s.

By the time Thursday arrives, there is poised to be broad troughing over the eastern half of the country. A big area of low pressure is expected to be centered over western Ontario, Canada and have an associated front which could drape all the way down the MS River Valley. This could bring us a better chance of  some showers and storms, but due to the standard summertime pattern we've just jumped back into, there is a chance every afternoon of a pop up storm or two, especially Wednesday through the weekend.

Tropical Storm Gert has weakened as the storm continues to venture over the open waters of the Atlantic, with max sustained winds as of 11am at 40mph. Gert will degenerate over the next day or so and will not pose a threat to the US.

There is another area of interest near the Lesser Antilles, on which the National Hurricane Center has placed a 20% chance of tropical cyclone development over the next 48 hours. This tropical wave will need to be watched closely as it migrates west into the warm Caribbean waters.