Archive for December, 2010

Supercells are now becoming a problem in the Jackson forecast area.  These two tornado warned storms are just southwest of Jackson.  Nothing has been reported on the ground with damage at this moment, but these cells are exhibiting strong rotation. 

Tornado watches are in effect for virtually the entire state of Mississippi throughout the evening into the overnight.  Stay aware of the weather situation as this activity could spread into west Alabama…..especially west of I-65 during the overnight hours.  More to come…

I don’t like to hear of fatalities when I get up in the morning…..and we already have three in the small community of Cincinnati in Washington County, AR from and early morning tornado that has destroyed at least one brick home and several structures.  Tornado watches and warnings continue to be in effect for portions of Northern Arkansas and Southern Missouri at this hour.

These storms intensified rapidly as they pushed across the OK/AR state line this morning into the warm, juicy flow of air coming northward out of the Gulf of Mexico.  There is more potential for such an event to unfold further east today.

The 12z sounding from Jackson, MS indicates a loaded gun type setup with quite the inversion around the 775mb level of the atmosphere.  This dry air aloft will likely aid in developing potential instability that could be unleashed if this cap breaks.  Given the incredible shear values…. it is likely that storms/showers will spin from the near the onset ahead of a massive mid level trough that will shoot northeast later in the period.

Our in-house mesoscale WRF model indicates that the capping should be broken shortly after noon with convection firing across most of Mississippi and potentially into west Alabama.  Shear values will be supportive of super cell structures with the potential for tornadoes.  This is a developing situation and one that we will possible deploy on for a chase within the next hour or so.  Stay tuned for more updates regarding this potential.

The first shortwave of the week is traversing the western portions of the Gulf Coast at this hour with widespread rain developing across LA/TX/MS ahead of the main impulse.  A weak wave of low pressure has developed across the south-central plains. 

Some shower activity spreads as far north of Indiana and Kentucky, but the main bulk of the rainfall is located along the coastal sections of Louisiana and Mississippi where some isolated occurrences of severe weather been reported.  A few funnel clouds and severe wind gusts have been reported along coastal sections of the Lake Charles, LA area…..near Pelican Island.

This activity will continue to spread northeastward and could reach the I-20 corridor later in the evening hours.  The heaviest totals of 1-2” are expected across LA/S MS with lesser totals further north.  This activity is expected to weaken as the shortwave pulls out and most of Alabama and Tennessee should remain dry per some of the latest mesoscale modeling that we have in house.  The potential for a more potent rainfall situation is in order for the New Years Day holiday.  We will dig into some data and have another post on the potential for heavy rainfall and maybe an isolated severe thunderstorm across portions of Mississippi and West Alabama on Friday.  

A few days before Christmas we were pegging on a potential Christmas winter storm that could plague parts of the southland with there first white Christmas ever.  This all turned to fruition during the early morning hours of the 25th and gave most of us what we had all been waiting for.  To the setup…

The night before the short range models started coming in more aggressive with precipitation.  These models started showing accumulations throughout the southeast region including north and central Alabama.  Here is a model image of the 00z BAMS model that is derived from Baron Services in Huntsville, Alabama.  Baron Services provides broadcast media with in house computer graphics for radar and weather modeling.

This model began showing the 2” criteria snowfall that is border line for a winter storm warning in this part of the country.  So, now that things began locking in on a greater snowfall potential we were watching this system develop from our homes.

The morning of Christmas Eve, December 24th, our system was developing in western Texas and to the north across the Dakotas.  We watched from our in-house system as the upper air system strengthened and moved across Texas as snowfall continued to move southward from Illinois, Iowa, Missouri, and Kentucky.

The surface low began to crank in far south Texas and precipitation was much more expansive that forecast by the short term models over portions of Texas, Oklahoma, and Arkansas.  This led many forecasters to believe that even with a more aggressive approach that the models may be coming in a bit too weak with the system.  The European, the most aggressive model of them all, was beginning to look like a good solution to place your bets on.  By the late evening hours and early morning hours on Christmas…..winter weather advisories/warnings began to fly.

It is nearly unheard of to have winter weather advisories down to Dothan, Alabama any time of the year much less Christmas.  However, this was a good call as snowfall began transitioning southward the morning of the 25th as our surface low transitioned along the coast with new upper level energy moving in to bring the colder air aloft with it.  Local radars began showing the transition zone as a “bright banding” feature.

Above is the transition zone around 10 am across portions of Jefferson, Shelby, and Talladega County Alabama on the leading edge of the precipitation.  This bright banding was due to some evaporation of the heavy precip. aloft.  It was reaching the surface in the form of sleet and snow as the column above cooled to isothermal.  In other words…..the heavy precipitation brought the colder air down with it to the surface allowing the mixture or changeover to all snow.  Basically….here was the end result for most areas.

Snowfall totals varied across many locations with Central Alabama receiving 1-2” in most cases with heavier totals of 4”+ in the Huntsville area.  Portions of Jackson County took 6” with power flickers being reported before the snow ended.  Black ice also became a problem when all was said and done as the cold air and windy conditions settled in.  Another winter weather advisory was required on 12/26 due to a large upper level low dropping in and bringing in colder air aloft allowing the low to wring out all over the moisture available in the atmosphere.

As the low moved northeast…..the BAMS models was pinpointing a potential major blizzard for the northeast.  Parts of NJ, NY, MA, etc. expected to get 2’ of snow!  Here is the BAMS model assessment of the situation from 00z 12/26.

Now…..here are the results from Vimeo user Michael Black of New Jersey.  These are images shot from a DSLR in a 5 minutes sequence during the blizzard.  Amazing 20” snowfall for these folks.

This is likely something that many of us in the south may never see again in our lifetime.  This is the first recorded white Christmas for parts of the Birmingham CWA since records have been kept.

Temperatures this evening just are not budging in parts of northeast Alabama.  The temps are still running below freezing from Heflin to Huntsville where icing is a major problem from the earlier freezing rain and sleet that we received.  Numerous motor vehicle accidents have been reported along with injuries.  Plain and simple…..if you don’t have to be out tonight stay indoors. 

We still expect this thermal boundary to move to the north eventually and bring everyone in the area above freezing….along with bringing some rain to us tomorrow.  The rain should be on the light side but temperatures will rebound into the 50’s and some places in the south will certainly get into the 60’s. 

We are now monitoring the potential for some winter mischief on Friday night as another compact  mid level wave comes across the region when temperatures will be conducive for frozen precipitation.  We don’t expect a major event AT THIS TIME.  I will say…..expect the unexpected when it comes to mother nature…..or plan for it at least.  We will bring you more up to date information following tomorrow mornings data.  We should have a better handle on the situation by then.

Alot of issues are ongoing and have already occurred with icing across the area from Troy on to the north.  The Freezing Rain Advisory has been allowed to expire west of I-65, but it’s still in effect until 3PM east of 65.  A total of 3 deaths have been reported thus far with many serious injuries.  Parts of I-59 have been closed as well.  Here is a look at surface temperatures and what to expect for the rest of the afternoon.

Icing potential should end for all areas including the far northeast counties by 5PM.  Warmer air is moving in from the SW and Jackson, MS is hovering near 60°!!  We should warm up even into the overnight hours and reach a temp near 60° tomorrow in Central Alabama.

Here is some video of the sleet/freezing rain from Childersburg.  YouTube didn’t convert very well, but you can see the traffic continuing with the icing ongoing as well as the ice bouncing off of vehicles and accumulating on stepping stones. 

Stay safe during the rest of your Wednesday afternoon.  Conditions will improve this evening.

We are watching the snowfall expand across the area now.  The low levels are still dry, but some reports have come in from areas such as Coker, Trussville, Cullman, and Huntsville.  The snow level is expected to continue to drop and some folks will experience some pretty decent snow bands this afternoon.  We will continue to watch the trends this afternoon and update with any potential for accumulations.

At this time….it looks as if the main shot at some snow really creating a dusting or so is in northeast Alabama.

La Nina is in full force as our forecaster, Fred Gossage, has explained in the post below concerning our potential weather effects ahead for most of the country.  Surface temperatures are well below normal and the waters below the surface continue to cool.  These temperatures are likely to reach the surface as we get “trade wind” bursts near the equator that occur every so often.  These bursts allow the water to churn or “upwell” just the same as the waters upwell during hurricanes.  This could have a rather large impact on our severe weather season down the road and we are monitoring it with a close eye in the forecast center.