Archive for January 10th, 2013
It has been a wild night of high winds across Central Alabama as a dying convective system triggered a gravity wave and wake low setup.
The result was widespread 40-50 mph sustained winds with some higher gusts. Winds just off the surface were roaring at near hurricane force. Luckily, we didn’t have any convection to bring those high winds to the ground.
But the 40-50 mph winds with frequent gusts above 60 mph did cause numerous reports of trees and power lines down. The result was scattered power outages.
Many trees fell on houses. Fortunately, we haven’t received any reports of injuries. There was significant damage to the roof of an apartment complex on Princeton Avenue in southwestern Birmingham.
The winds are slowly diminishing, but gusts in the 40-50 mph range could affect eastern sections of Alabama. Higher elevations could see higher gusts.
An interesting notes from Steve Jones at the Alabama Quake Center. He reports that the wind actually caused vibrations in the ground that were picked up by their seismographs.
“Thought you might be interested in what the passage of tonight’s gravity wave looked like at the AlabamaQuake seismic station here in Huntsville. It appears on the seismogram that there were THREE main pulses of winds in the wave’s passage thru Huntsville, with the first being at 8:27 pm, and the last at 9:09 pm, the seismic signature being created due to the pressure impact of the gusty winds on the surface of the local terrain and the trees rooted there; the ground’s vibrations are of course detected on the seismograph.”
And thanks to our skywatchers tonight for their excellent reports!
Tomorrow will be showery but mild, with highs around 70F.
Crazy winds are blowing across Central Alabama, including the Birmingham Metro now.
John Talbot says Homewood PD reports transformers blowing and power going out in parts of the city.
John Talbot and Bryan Falls report a tree down on a vehicle on I-22 at the Flat Top exit.
Windows are reportedly blown out of homes in Pleasant Grove.
Hoover PD reports tree down at Woods of Riverchase Drive and Summit Drive.
Hoover Fire reports tree down in 1200 block of Chester Street.
Be in a safe place as these strong winds blow across eastern Jefferson and Shelby and Chilton Counties, pushing into St. Clair, Talladega and Coosa Counties.
Peak wind gusts from our SKYCAM network so far…
Tuscaloosa (atop the Tuscaloosa County Courthouse) 74 mph
Oak Grove (Cliff’s Natural Resources) 57 mph
Birmingham (atop the Daniel Building downtown) 41 mph
Cullman 36 mph
Jasper 29 mph
The period of highest winds with this gravity wave/wake low event lasts about 15 minutes, but strong winds are lasting about 30 minutes in most areas.
We have reports of trees and power lines down over Tuscaloosa, Sumter, Pickens, Fayette, and western Jefferson Counties. Power is out in some places.
Winds in the Birmingham metro will average 35-45 mph over the next 30-45 minutes, but gusts could be higher. We don’t have much skill in forecasting these kind of events since there is nothing to show on radar, generally speaking. And, the intense pressure fall/rise couplet is hard to track since there is no real dense surface reporting network.
Scroll down for the details, but this event is not directly related to thunderstorms, and there is no threat of a tornado. A non-preciptation, high wind event.
Stay tuned for updates as needed…
Winds just gusted to 57 mph at the Oak Grove Skycam according to James.
The 40-50 mph winds with gusts to 60 mph will continue to spread across much of Central Alabama including the Birmingham Metro over the next hour.
Be ready for weaker trees to be blown down. Some powerlines will be affected. Try to be inside away from the threat of falling trees when the winds approach.
A high wind event is moving across Central Alabama tonight.
It has caused numerous reports of downed trees and powerlines, especially across the Tuscaloosa Metro.
A tree was just reported down by the Jefferson County Sheriff’s Office on Warrioir River Road near Steve’s Grocery according to John Talbot.
Ryan Stinnett, one of our meteorologists, reports power is out in parts of western Jefferson County.
Richard Viola reports tree down in Duncanville by the Eagleville FD station. Trees were reported down Samantha in northern Tuscaloosa county.
Winds gusted to 63 mph just before 8 p.m. at East Edge Apartments in Tuscaloosa, on the eastern side of the UA Campus.
Be ready for winds of 40-50 mph with some higher gusts as this gravity wave/wake low pushes east across Central Alabama.
The winds will mainly affect parts of Bibb, Blount, Chilton, Dallas, Hale, Jefferson, Marengo, Perry, Shelby and southeastern Tuscaloosa Counties through 9:30.
Winds have gusted to 57 mph at the Tuscaloosa County Courthouse tonight due to a wake low/gravity wave on the back side of a departing rain mass.
Power is out across parts of the city of Tuscaloosa, and many reports of trees and power lines have been received via social networks.
Scroll down for an explanation of this kind of event… the winds are not the direct result of a thunderstorm, and there is no risk of a tornado. The winds are happening, in fact, with no rain.
Winds are averaging in the 35-45 mph range, with gusts to 50-55 mph. The peak winds last about 15 minutes, and then they begin to die down.
The higher winds will impact the Birmingham metro, if it holds together, by 8:45 or so. But remember, this is not a thunderstorm event, it is an entirely different situation, and it remains to be seen how long the high winds will last as the band moves east across Alabama tonight.
Strong winds are reported over much of West Alabama this evening… on the back side of a departing rain mass…
Trees have been blown in a few spots over Sumter and Pickens Counties; from most reports it seems like winds are averaging 35-45 mph, with higher gusts.
LATE NOTE: We just recorded a peak wind gust of 57 mph atop the Tuscaloosa County Courthouse. Now getting reports of trees down across Tuscaloosa and Fayette Counties…
The band of high winds will move east, and could possibly impact the Birmingham metro by 8:45-9:00 p.m. The period of high wind lasts about 15 minutes, followed by a slow decrease in wind speed.
These highs winds are NOT related to thunderstorms directly…
The winds are the result of a wake low/gravity wave combination… I think Kirk Mellish has a good simple explanation…
“A big complex of rain and thunderstorms can push up a lot of air, it then falls back to earth, which causes a rapid change in temp and air pressure over a short distance putting the atmosphere out of balance, the wind accelerated as nature tried to get the atmosphere back in balance or equilibrium. A small mountain of air (high) was followed by a hole in the air (low). The wind rushed from the mountain to fill the hole. The steeper the grade or gradient between the two the harder the climb or the harder the wind. Nature trys to equal out the two to reach a flat known as a stasis. Ocean waves are another example. A rock dropped into a lake and the resulting splash and waves that radiate out from it are another example.”
We are better at identifying wake low/gravity wave setups, but often it can happen without any warning. This is an entirely different process than winds directly from thunderstorms.
The winds will die down later this evening…
Thunderstorms that have been severe sporadically across Mississippi and Louisiana have weakened as they have moved into the more stable air over West Central Alabama this evening.
They are mainly affecting southern Pickens, Greene, Sumter and Choctaw Counties. They will move into Tuscaloosa, Hale and Marengo Counties in the next hour.
Other heavy showers have formed ahead of the main line, from southern Shelby and Coosa through Chilton and into Autauga and Lowndes Counties.
We can’t really call these showers thunderstorms, since they don’t seem to have much if any in the way of lightning. No lightning was observed at Meridian as they passed. Winds did gust to 35 mph though.
And winds gusted to 40 mph at Tupelo on the back side of the rain area. There was some tree damage in the Tupelo area.
LATE REPORT AT 6:24
NWS says there are reports of winds of 45 mph in Sumter County.
BACK TO ORIGINAL POST
Interestingly, the winds will be mainly on the back side of the rain area, unlike our typical storms that feature the wind on the front side.
So, rain and some gusty winds will be the only impact. There is no threat of severe weather.