Archive for August 5th, 2012
North Alabama Storms Dump Heavy Rains
Storms are over North Alabama at this hour. You can see the SPC slight risk boundary (the yellow line).
That storm over Marion County has been dumping some copious ranfall. A blog reader reported three inches in 30 minutes with intense lightning.
That report is certainly supported by this storm total rainfall estimate.
The NWS has issued an aerial flood advisory for parts of Marion County. Flooding in poor draining areas is likely.
Be careful of the lightning as well.
Slight Risk Area Today/Tonight Over Northwest Alabama
Showers and storms were increasing in coverage and intensity this morning from northern Mississippi into Tennessee. They are just northwest of the very northwest corner of Alabama. They are forming in a convergence zone ahead of a cold front that stretches from southwest to northeast from near Dallas to Little Rock to Indianapolis.
Clouds are pretty thick northwest of a line from Hamilton to Athens across Northwest Alabama. South of there, skies are partly cloudy, with increasing sunshine the further south you go.
A peek at the Birmingham morning balloon release indicates a pretty moist airmass well up into the atmosphere. Preciptable water values are about 25% higher than yesterday. When temperatures reach the lower 90s as forecast for this afternoon, instability levels will be moderately high, around 2,500 j/kg. Scattered storms should develop across the rest of Central Alabama as soon as temperatures reach the middle 80s or so. There is very little shear, so the storms will be typical summeritme pulse storms that go up quickly and rain themselves out.
Storms will be more common and stronger over Northwest sections. The SPC has a slight risk severe weather outlook, their standard forecast for elevated chances of organized severe weather this afternoon and overnight north of a line from Hamilton to Decatur to Scottsboro. This is because of the proximity to the front.
TROPICS
No new big news on Ernesto and Florence. Ernesto is poorly organized and moving westward at a rapid clip. Top winds are 50 mph. The pressure was back down a bit, to 1006 mb. The system looks poorly organized on satellite imagery. It seems to be running into dry air and the fast forward motion can take a toll on a tropical system as well. Still expecting Ernesto to cross the Yucatan on Wednesday, move over the southwestern Gulf and make landfall in southern Mexico on Friday. Florence has stopped strengthening over the eastern Atlantic. Florence is expected to weaken over the next few days as it moves west northwestward to a point north of the islands on Thursday. It will probably dissipate after that.
Showers, Showers, and More Showers
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Our weather pattern will continue to be active for the foreseeable future with some pretty good chances for rain today and Monday thanks to the approach of a weak front. SPC even suggesting potential for severe storms especially in the Tennessee River Valley today and tonight with damaging wind and marginal severe hail possible.
The strong trough moving across the Great Lakes will be responsible for dragging a cold front into the Tennessee River Valley today and Monday. In the upper atmosphere, the Bermuda High to the east and the persistent ridge to our west will connect today, however, the connection is short-lived as another strong trough moves in quickly behind this first one to help to reestablish the trough over the eastern US. At the surface, there is the front approaching from the northwest which should help to add thunderstorm development in the heat of the day plus a weak inverted trough moving toward the west across the Gulf coast. So two distinct features each helping to improve rain chances for the northern and southern sections of the state.
This means that we should stay in a fairly active pattern for the next week or so with rain chances up due to the presence of the frontal boundary plus we get back into a northwesterly flow pattern. The atmosphere does not change much so we remain moist for daily shower chances.
Rainfall amounts are likely to be between 2 and 3 inches for some locations during the next 5 days. As we noted yesterday, many of the storms were slow moving resulting in heavy rainfall in isolated locations. The relatively slow movement of storms should keep this threat with us for the next several days, too.
Tropics are active with Florence and Ernesto. Florence defies forecasters by maintaining herself, but she remains a threat primarily to open waters of the Atlantic. And Ernesto continues to chug steadily across the Caribbean with some weakening. Ernesto seems to have a bead on the Yucatan Peninsula and could become a hurricane before reaching the coast there. Current guidance continues to show a slightly more southerly track which would bring the storm into the southwest Gulf of Mexico on Thursday and Friday. My concerns for the troughiness over the eastern US are not as high with a slightly more southerly track, but I am still wary of how the two might interact as they get closer. So for now it looks like the western Gulf remains the primary risk area.
Looking into voodoo country, the GFS shows a messy pattern with a continuation of the western ridge and a sizable storm in the Atlantic around August 20th.
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Thanks for staying tuned to the Weather Xtreme Video. James Spann should be up first thing tomorrow morning with the next edition. Stay with the Blog for the latest information on the weather across Central Alabama. Have a great day and Godspeed.
-Brian-
