Updated 800am CT – Tuesday / 16 September 2014
…. An Unsettled Weather Pattern ….
…. Passing Upper Air Low Pressure Disturbances with Better Rain Chances ….
On this Tuesday morning…. a weakening stationary front extends west southwestward from southern Alabama and Mississippi across southern and central Louisiana into southeast Texas and the Texas coastal plains. As a result of this surface weather pattern, our local surface winds are east northeasterly.
In the upper levels of the atmosphere… a broad trough.. or line.. of upper level low pressure is moving eastward through the eastern half of the USA with another trough of low pressure is situated off the west coast. The upper air reflection of tropical cyclone Odile.. with abundant high and mid level Pacific moisture.. is located over the central Baja Peninsula. Weakened upper level high pressure.. acting like a lid on the atmosphere.. extends eastward from eastern New Mexico and Texas east southeastward over the Gulf of Mexico and Florida. As a result of this pattern, the upper level winds over south central Texas and the Austin metro area, about 18,000 feet above the ground, are westerly less than 20 mph.
With the upper level trough to our northeast, the upper level high pressure area (think.. “the lid on the atmosphere”) has continued to weaken a little and shrink in size as upper level winds increase a bit from the west and the system itself settles southward a bit.
As the weakening front over south Texas drifts northward, more clouds and abundant low level moisture continue over the area today and tonight through tomorrow and Thursday. At the same time, upper air disturbances and mid and upper level moisture.. from the west.. traverse the area and result in the return to rain and thunderstorm chances over the next couple of days. With cloud cover and precipitation chances over the next couple of days, afternoon high temperatures remaining at or slightly below seasonal averages.
By Friday into the weekend, the upper level high pressure ridge (the “lid” on the atmosphere) will strengthen a bit with rain chances coming down and clouds thinning out a bit.
Guidance suggests that another cold front will move southeastward across the area by Monday with another better chance of rain showers and thunderstorms.
Regarding my forecast, my local forecast confidence: My forecast confidence over the next two to three days is high (still concerned with exact rain timing and amounts). My confidence is high to very high Friday through the upcoming weekend. My forecast confidence falls back to medium to high for Monday in reference to precipitation and frontal timing.
Have a good Tuesday….
Meteorologist Troy Kimmel
Contact me:
tkimmel@austin.utexas.edu
http://www.facebook.com/troykimmel