Archive for December 24th, 2012
WeatherBrains Episode 361 is now online (December 24, 2012). If you are crazy about weather, this is THE netcast audio program for you!
There are no guests or panelists for tonights show, so we use this opportunity to talk about a variety of weather sites that we find useful in a variety of topics.
Other discussions in this weekly podcast include topics like:
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From The Weather Center:
WeatherBrains 101: Troughs come in a variety of types including positive, neutral, and negative. So what determines what kind of trough it is. And especially what does a negatively tilted trough mean? We explore the characteristics of a negatively tilted trough.
Listener Surveys: Okay, we continue to drive this topic into the ground, but we really do like to hear from you. Many thanks to everyone who has taken the time to fill out the Listener Survey. The survey takes just a minute or two to complete and provides us with an opportunity to learn where you are and hear your thoughts and comments on the show. Click here to take the survey.
WeatherBrains Picks for Every Weather Enthusiasts
National Hurricane Center
The WeatherBrains crew includes your host, James Spann, plus other notable geeks like JP Spann and Brian Peters. They bring together a wealth of weather knowledge and experience for another fascinating netcast about weather.
I hope you and your family are enjoying a peaceful Christmas Eve. Parameters are still coming together for a high impact severe weather threat for Alabama tomorrow…
You can watch Brian’s morning Weather Xtreme video for a meteorological discussion of tomorrow’s threat.
Below are the SPC severe weather outlook maps for tomorrow and tomorrow night…
Note the “hatched” are on the second map; that means there is a 10% or greater probability of significant severe weather within 25 miles of a point. And, SPC defines “significant severe weather” as F2 or greater tornadoes, damaging winds with speeds greater than 65 knots, or large hail 2″ or greater in diameter. The “hatched” area runs from Southeast Texas to West Georgia, and includes basically all of North-Central Alabama.
But we stress the severe weather risk includes ALL of Alabama.
See the STP (Significant Tornado Parameter) index tomorrow night, as projected by the NAM model…
WHAT TO EXPECT: Storms tomorrow afternoon and tomorrow night could produce hail, damaging wind, and tornadoes. Considering the atmospheric setup, a few strong/violent tornadoes are possible, especially south of I-59/20, and west of I-65. But again, the risk of severe weather is statewide. Doesn’t make much sense to ask about any specific county, town, or neighborhood in this case.
TIMING: While severe storms could develop in West Alabama as early as 3:00 tomorrow afternoon, the primary threat will come from 4 p.m. tomorrow until 3 a.m. Wednesday.
Below is the RPM model output, valid at 9:00 CST tomorrow night…
TRAVEL: If it all possible, we recommend that travel tomorrow across any part of Alabama will come before 3:00. If you have to travel by car after 3:00, be sure you have a good source of getting severe weather warnings. And, remember, many radio stations could be “unmanned” tomorrow. You can always hear ABC 33/40 audio during our long form coverage on your smart phone via the ABC 33/40 app.
SNOW TO THE NORTH AND WEST: If you are traveling, here is the latest snow projection on this storm system from the NAM…
This will be a whopper of a snow storm in the cold air north and west of the surface low. And, here in Alabama, Wednesday will be cold and raw with falling temperatures. Some light snow, or snow flurries, are possible over the northern counties, but accumulation is not expected.
CALL TO ACTION: This is a challenging outbreak because it falls on Christmas Day. Many will be traveling, and we won’t be able to reach people effectively. First off, since many people aren’t as connected to the weather as you, please pass this along to your friends, neighbors, and anybody else you come in contact with today so they will be aware of the situation.
BE ABLE TO RECIVE WARNINGS: Never, never, never rely on an outdoor siren to let you know a tornado is coming. That is dangerous, and no telling how many Alabamians have been killed by this “siren mentality” over the years. They reach a limited number of people outdoors, and that is it. The baseline is having a NOAA Weather Radio in your home, properly programmed, and with fresh batteries in case of a power failure. Also, having a good smart phone warning app is even better. We recommend iMap WeatherRadio for iPhone and Android phones, and MyWarn for iPhone. Both will warn you ONLY if you are in a warning polygon (remember, warnings are not county based), you can program in fixed locations, and most importantly, you can watch live ABC 33/40 severe weather coverage within the app.
Yes, I am very active on social media, but remember on Facebook you won’t see all posts coming from me within your newsfeed unless you subscribe to my regular account (NOT friend request… subscribe) and choose to receive all updates from me. Here are all my social media accounts…
KNOW WHERE TO GO: If you live in a mobile home and you are in a tornado warning polygon, you must leave. Remember, tomorrow is Christmas and many typical safe places will be closed. Think about it and be ready. And, if you live in a site built home, the safe place is a small room on the lowest floor, away from windows, and near the center of the home. Have readiness kit that includes helmets for everybody in the house, flashlights, extra batteries, shoes, medication, etc.
Again, please do NOT be alarmed by this threat. Enjoy today and tomorrow with your family and don’t worry. But, be aware of the threat and have a way of getting the warnings, and have a plan, and we will all be fine. Stay tuned to be blog for running updates…
Just a quick update on Alabama’s weather on this Christmas Eve:
Visible satellite imagery shows that blue skies have broken through over much of the state. Skycams back up this thought. Looking at the imagery, you an see “streets” of stratocumulus clouds from south of Huntsville southward through Birmingham, Tuscaloosa and Montgomery down to about Greenville. These have formed as a result of sunshine warming the lowest layer of the atmosphere and making it slightly unstable. The streets form thanks to the low level flow which is west to east ahead of the surface trough and cold front.
That front is over Northwest Alabama extending back into Mississippi south of Jackson. Some deeper convection is located along the convergence zone of the front, but radars show that it has been unable to produce any precipitation.
The only rain left in the state is down around Dothan in the southeast corner.
Temperatures are in the middle 50s in the I-20 corridor and will warm a couple of more degrees for the afternoon highs. Most locations will be back in the upper 40s to near 50F by morning. Skies will be partly cloudy overnight, although I suspect some low clouds and fog may fill back in as the moisture is not going to be really scoured out by this front, that will stall across Central Alabama.
The threat of severe weather seems more like a cruel April Fools Day joke than a Christmas present, but damaging winds and tornadoes are a very real possibility for tomorrow and one that everyone in Central Alabama must take seriously.
Scroll down for more information on tomorrow’s severe weather situation and check back frequently for updates this afternoon, overnight and all day and all night Tuesday night.
Here are a few notes or random thoughts about the upcoming weather situation. This is not an organized post but rather some thoughts swirling through my head.
Now: Most of the rain has cleared the Interstate 85 corridor, so little additional rain is expected across Central Alabama. Some spots especially across the western half of the state are seeing some sun, a bit earlier than I thought we would. But there is also another mass of clouds back across northwestern Mississippi that may curtail some of the sunshine. Temperatures are mild with readings ranging from the mid 50s in the eastern areas to the lower 60s in the west central counties.
Models: The various computer models continue to be in good agreement on the track and development of the low pressure storm system that will affect us Christmas afternoon through early Wednesday. I have some concerns that the latest models, those that work in the shorter terms, are coming in somewhat stronger with the strength of the surface low. If the surface low is stronger, then conditions are likely to become even more favorable for severe weather and they are already favorable.
One model concern I have is that the GFS may not be initializing well. I was looking over the MOS numbers and dew points are not projected to get above about 53 degrees in Birmingham. But the current dew points are already higher by about 5 degrees than the MOS numbers for noon today! It also appears that the GFS MOS numbers are too low on the strength of the wind flow especially if the surface low is stronger. One of the short range models, I think from SPC, was showing a 994 millibar low. That kind of strength could mean severe weather conditions push into the Tennessee River Valley.
Severe weather parameters: Looking across the severe weather parameters, it appears that we have a low CAPE and high shear environment. While CAPE which provides information on instability is low with values at or below 700, those values are sufficient for severe weather. The high shear means that storms will be rotating. We should see high low level moisture values with dew points reaching near 60 or perhaps edging into the lower 60s. And it also appears that the storms will be rooted into the boundary layer with LCL (lifting condensation level) values low.
Serious: There is no doubt in my mind that this is a serious situation. Everyone needs to take it seriously. People are going to be distracted due to the holiday as we should, so it is imperative that everyone be aware of the severe weather threat and have a way to receive weather warnings tomorrow. And whatever that method is, do not be turning it off for Christmas dinner or other activities. And remember, don’t rely on outdoor weather sirens.
An all new edition of the ABC 33/40 Weather Xtreme video is available in the player on the right sidebar of the blog. You can subscribe to the Weather Xtreme video on iTunes by clicking here.
Rain and embedded thunderstorms should come to end across much of Central Alabama late this morning. At this writing, most of the radar echoes were from Birmingham east and south. By late this afternoon around sunset time, we might even see a few peeks at the sun if we can get some breaks in the clouds.
The next trough, and a significant one at that, comes our way from the southern Rockies on Christmas Day. A surface low will form in Southeast Texas and then move northeastward across the Tupelo/Muscle Shoals area to near Nashville by Wednesday midday. Both the ECMWF and the GFS are in good agreement on the positioning and strength of the surface low which generates good confidence in the unfolding weather scenario. Looking closer at the severe weather parameters, instability is not tremendous but it is sufficient for severe weather to occur. Surface dew points are expected to climb to around 60 or so Christmas afternoon, giving us plenty of low level moisture for the strong storm system to work with. Shear is abundant with Bulk Shear values well above the 40 threshold for rotating storms. And while I did not mention it in the video, the LCL levels are low which the NWS in Birmingham has found to be a favorable element in severe weather events in Central Alabama.
After the surface low moves into Tennessee on Wednesday morning, cold air arrives as the moisture is departing, typical for us. There may be enough moisture as the cold air arrives to see the light rain mixed with some light snow or perhaps the precip to change over to snow flurries before ending completely. See the video for the parameters for this including 850 temperatures and precipitable water.
Winter weather is going to be a factor for the Central US from Oklahoma into Ohio. Winter storm watches have already been posted for the swath of the US where 2 to 4 inches of snow is likely to occur. If you have travel plans north and northwest of Birmingham, you may want to check on road conditions so you can make your travel as safe as possible.
The upper trough and the surface low move into the Mid-Atlantic states on Thursday allowing us to dry out for Thursday and Friday. It will be chilly with lows dipping into the 20s and highs in the 40s warming into the 50s Friday. Rain returns to the forecast on Saturday with the approach of another upper level short wave. This one zips by so the rain should be confined to Saturday with dry conditions returning on Sunday and Monday. Temperatures do stay seasonal as we head to the end of 2012.
The big message from the GFS long range projections is that the overall pattern remains pretty dynamic with quickly moving troughs providing us with weather systems about every two to three days. There does not appear to be any really cold or really warm patterns for the first week of January, although, the pattern around the 8th would suggest a substantial cold shot perhaps for the 10th or so, but then that is really far out!
And you can follow news and weather updates from ABC 33/40 on Twitter here. Stay in the know by following the whole gang – here’s the list…
|James Spann||Charles Daniel||Ashley Brand|
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Just a reminder that we remain on a one-a-day schedule until the start of 2013. But stay up with the latest weather information by checking with the Blog for later posts. You can also catch my weather forecast on ABC 3340 at 5, 6, and 10 pm today. Be safe and Godspeed.