Snow Chances Continue

Now about 24 hours away from a potential winter weather event and snow chances continue for parts of Mississippi. Here is tonight's update:

Upper level energy is beginning to dive southward across the four corners and into the southern plains over the next 12 hours. As this happens, low pressure is still expected to develop in the Gulf of Mexico. Cold air will be coming in tomorrow night and the atmosphere should also cool as precip. begins to fall tomorrow evening. The big question tonight is where does the surface low track? The further south it goes, the less moisture we will have to work with. The further north it tracks, the more moisture we will have to work with and snow chances would potentially go up north of the I-20 corridor.
While there are some differences in the various computer models regarding the track of the surface low pressure system in the Gulf of Mexico, the general trend is for the low to track close enough to us that moisture will manage to get into our area. The first areas to see any precipitation will be southwest Mississippi (Natchez area) and this will be all rain albeit a cold rain. As the evening progresses, the temperature through the atmosphere will cool off. With deeper cold air in place, the rain will change over to snow. There may be a few sleet pellets mixed in as the rain changes to snow, but mostly snow is expected with deep cold air in place.

The next question is how much? This snow will be fairly wet, as it is often the case here. Wetter snows don't accumulate as much as a dry snow would. In the case for tomorrow night, snowfall to liquid water ratio will be roughly 10:1. This means if we got 1" of rain out of this system, it would equate to 10" of snow. Models indicate that this system will produce roughly .20" to .30" of precipitation across south Mississippi. This would translate into about 2-3" of snow. Again, there are differences in the models. Here are some snapshots from a program called Bufkit, which is a program that allows us to visualize and analize model data for precise points and times. The top image is the GFS model for McComb. The bottom image is the NAM model for McComb.

 In both of these images we are looking at precipitation amounts and type, represented on a bar graph. The time scale is at the bottom of the images and you read it right to left. The GFS model is in 3 hour increments, while the NAM is in hourly increments. The blue bars mean snow, the green bars are rain. On both models I have labeled only the total liquid accumulation of snow forecast by the model. You will notice that the GFS model 0.083", which would be less than an inch of snow given a snow ratio of 10:1. You will also notice the GFS model does not show any rain coming in before the snow.

The NAM model shows some rain coming in Friday afternoon into the early evening hours (green bars), then a changeover to snow (blue bars) from mid-evening Friday into early Saturday morning. The NAM also shows a total of 0.220" of liquid resulting from the snow. This would result in roughly 2"-2.5" of snow.

Right now it appears that the most snow will fall south of the I-20 corridor, where Winter Storm Watches are in effect. The metro area may end up seeing just a few flurries or light snow shower out of this. Again, the differences in snowfall amounts are tied to the position of the surface low and where it tracks. Any change in this will greatly impact the forecast.

This won't be a system to keep you snowed in for days on end, but could cause some minor travel problems late tomorrow night. Everything will be out of here by sunrise Saturday, so if you sleep late on the weekends, you may miss it!

I will post another update tomorrow and of course you can tune to WLBT for more information.

Eric - elaw@wlbt.com

Mississippi Snow?

The GFS computer model picked up on the idea of some snow for parts of Mississippi several days ago. At the time, it was the only model forecasting this. Over the past 24-36 hours, additional computer models have come on board with the idea of some winter precip. across central and south Mississippi from late Friday into early Saturday. It became increasingly hard not to mention snow in the forecast starting today, now that we have additional models headed towards a similar solution. 

Of course, regardless of the time of year, snow forecasts in Mississippi are always hard and almost always change. At this point, we're roughly 48 hours away from the start of the event and no forecast is certain at this point. Too much could go wrong.

The general set-up for this will be for a surface low pressure system to develop somewhere in the northwestern Gulf of Mexico just as a pretty decent upper level disturbance begins to move in from the west. This surface low pressure system will send moisture back our way in the form of rain, during the daytime hours Friday. No doubt any precip. Friday afternoon will be of the liquid kind as temperatures will be 15-20 degrees above freezing. The upper level disturbance will come in Friday night as temperatures begin to cool off in the atmosphere. This is what we have to watch since any moisture still in place could fall as snow. 

As I mentioned eariler, lots of things can go wrong. As always, the lack of sufficent moisture is often a problem around here. If that low pressure tracks too far south, there won't be much moisture for the upper level disturbance to work with. Also, in a way the cold airmass actually works against us since it is not only cold, but also dry. We could easily end up with snow in the clouds...but nothing make it to the ground because of the dry atmosphere. Right now my gut tells me this is likely what will happen.

Even if we do manage to see some snow, it will be light and it may not even accumulate. We've really not been cold for a long period of time around here. Remember, we had high temperatures in the 70s on Sunday. The ground temperature isn't all that cold and of course road surfaces are still pretty mild. Any accumulation would be very short-lived and likely on grassy surfaces and maybe some cars. Roads may be slick, but that would likely be due to them just being wet and not because of snow. So the bottom line is don't get your hopes up with this system. Don't run to the store to stock up on bread and milk. As new model data comes in, we'll be updating you on WLBT. I will also post an update here tomorrow.

Eric - elaw@wlbt.com

Atlantic Hurricane Season Ends

The 2009 Atlantic Hurricane Season came to a close yesterday and as mostly expected it was a pretty quiet season. Here is how it shaped up by the numbers:

• Named Storms
• 2009 - 9
• Average - 11
• Hurricanes
• 2009 - 3
• Average - 6
• Major Hurricanes (Category 3 or higher)
• 2009 - 2
• Average -2

This graphic from NOAA shows the tracks of this year's storms. This year only two storms impacted the US mainland. This included Claudette and Ida, both of which made landfall only roughly 100 miles from each other. Both systems were tropical storms at the time of landfall, making this the first time in three years that a hurricane has not hit some part of the US coast. This year also had the fewest named storms since 1997. One other interesting tidbit, there were 38 hurricane hunter flights this year. In 2008 there were 169. This really gives you an idea of how less active it really was. The slow hurricane season was due to the El Nino that formed early in the hurricane season. El Nino is when the waters over the over the eastern tropical Pacific are unusually warm. El Nino has big impacts on global weather, including the hurricane season the Atlantic. El Nino causes there to be strong winds in the upper part of the atmosphere blowing against systems that try to become tropical storms or hurricanes. These strong winds are called wind shear and they make it very hard for systems to develop and mature. This is why the season was not very active El Nino conditions will continue through the winter months, but it is uncertain if it will still be going on as we go into the 2010 hurricane season.

Eric Law - elaw@wlbt.com

Ring Around The Moon

If you thought the world was ending last night because of the halo that appeared around the moon for few hours, you were not the only one! The WLBT newsroom was flooded with calls by worried viewers wanting to know what was going on in our sky. In case you missed it, here is a photo that was sent in from a viewer in Hattiesburg, MS and forwarded to me by Tanner Cade at WDAM-TV, our sister station in Hattiesburg.

(Please note that this picture appears very distorted in Google Chrome and FireFox web browsers.)

In addition to the phone calls, we had dozens of e-mails and several posts were made to the First Alert Weather Facebook fan page.

So what caused this unique feature in the sky? Well, believe it or not, it isn't that UNcommon. Here is how the halo is formed.

Last night we had a deck of high, thin clouds in our sky. These are called cirrus clouds. Specifically they were cirrostratus clouds, meaning they they were sheet-like and high in the sky. These type clouds are composed of ice crystals, rather than water droplets, because the temperature is below freezing that high in our atmosphere. When these clouds are present, light, in this case moonlight, gets bent by the ice crystals. The net result is a halo around the moon. You can even get halos around the sun, but those are much harder to see since the "background" is blue. Halos at night are much easier to see since the "background" is black. Last night's halo was very visible since the moon was almost full. I think this is what prompted the large number of calls to the station. Halos are actually fairly common. We usually see them ahead of weather systems that bring rain (in colder climates snow), like fronts. In fact, there is a weather saying that goes something like "Halo around the moon, rain or snow soon." And of course, what did we wake up to today? Rain! After a couple of hours yesterday evening, the clouds thickened and the halo disappeared.Next time you look in the sky and see a bright circle around the moon, don't sweat! The world isn't ending. It just means there is probably some rain in the near future.

Eric - elaw@wlbt.com

Rainy For A Day or So

Wouldn't you know that rain would return just in time for the weekend? Low pressure has developed in the northwest Gulf of Mexico. This low pressure will track east-northeast and remain south of our area today. The low will still be close enough to bring us lots of clouds and some showers. Rainfall amounts look light in most areas. Rain will be heaviest in south Mississippi/Coastal areas...closer to the low pressure area. Here is map showing the low pressure area by this afternoon.

The low pressure will move east of our area tomorrow morning, taking the rain with it. We should see some sun by afternoon.
Eric - elaw@wlbt.com

Remembering Woodie

On Friday former WLBT-TV Weatherman Woodie Assaf passed away at the age of 92. Woodie started working at WLBT when the station signed on the air back in 1953. He continued to work at the station giving weather until he retired in 2001. He was a TV weatherman longer than any other in the country.

I never had the opportunity to meet Woodie as I didn't come to WLBT until several years after he retired. However, almost everywhere I've gone since working at WLBT, someone has always passed along to me how much they miss Woodie, or how watching him tell the weather was a part of their daily life. It is clear that he had many dear fans and he is part of why WLBT is what it is today.

Woodie did more than just give the weather. He donated a lot of time to charity work, raising large sums of money. Before coming to WLBT, Woodie worked in radio. In a business where a lot of people don't last 20 years, Woodie stayed with broadcasting for over 60 years. He was clearly dedicated and loved his job. Most of all, he loved people. He will be missed.

I wanted to take a moment to refelect on this good man and ask that everyone pray for his family.

Eric - elaw@wlbt.com

Ida A Tropical Storm

Good news this morning as Ida has lost strength over the last 12 hours. After topping out as a strong Category 2 storm with max sustained winds of 105 mph yesterday, this morning Ida's winds are down to 70mph. This makes Ida a strong tropical storm.

As I talked about last week, Ida is now starting to move into cooler water and this will continue to be the case as the storm heads north. Also, as noted on this satellite imagery, strong winds aloft are shearing the tops of the storms around Ida off. The deep oranges on the satellite imagery are the higher, colder cloud tops associated with the system. As you can see, most of that is now north/northeast of the center of circulation (shown by the tropical storm symbol). There is not much storm activity around the center. These strong winds aloft are not going to let up. So that, along with the storm moving into cooler water, means that Ida's days as a tropical cyclone are just about over. The storm will then begin to transition from a tropical system, into more of a hybrid type storm and eventually lose all of its tropical properties in the next 24 hours.
Regardless of the weakening, there will still be some nasty weather along coastal areas of Alabama and the Florida Panhandle. Here is the official track from the National Hurricane Center. You can see that the center of the storm is expected to come ashore near Mobile Bay very late tonight or early Tuesday. All Hurricane Warnings and Watches have been dropped, and now only a Tropical Storm Warning is in effect from southeast Louisiana eastward across the Florida panhandle. Once Ida is inland, heavy rains will be the big threat across east Mississippi, Alabama, Georgia, the Carolinas and parts of Virginia.

Eric - elaw@wlbt.com