Archive for January, 2009

Winter Storm Chances for the Southeast go Bye-Bye. Light, Accumulating Snow Possible Tuesday Afternoon – Wednesday Morning

Posted in Severe weather, Winter weather on January 31, 2009 by stormstream

Well heck. For the first time this winter I actually felt confident enough in the models beyond five days to declare that a major winter storm was likely for the Southeast early next week. The medium range models from five days and beyond have sucked this winter, and because for the first time this winter I actually bought into them, I sucked with this forecast. It’s just doesn’t look like it’s going to happen folks.

Despite the fact that the system hasn’t even made it over the U.S. to be sampled by weather balloons, there is just simply to much overwhelming evidence in the models that this thing is going to stay weak and way down in the Gulf of Mexico. Most of us will be lucky to get a dusting of snow, and consider yourself amazingly fortunate if you pick up an inch or two.

Now having said that, I will also say that I am not ready to totally write this system off. I want to see what the models show at 0z today after the system has been fully sampled and real data has been ingested in the models. Thighs could dramatically change. I’ve seen it happen before. However, I do not think the chances are very good that we will see much of a change to bring significant snow chances back to the Southeast. I hope I’m wrong.. again. lol

But all is not lost for the snow-starved, snow lovers of the Southeast. The forecast models show a clipper system diving southeast in the northwest flow aloft on Tuesday. This system would zip across TN and enter northern MS and northwest AL Tuesday afternoon, then sweep across the rest of central and northern AL, central and northern GA and SC Tuesday night, and affect central and eastern NC on Wednesday. It will be plenty cold enough for the precipitation with this system to fall as all snow. It will be moisture-starved, but with high ratios of one inch of liquid water producing 15 to 20 inches of snow, you can 1 to 3 inches of powder out of not a whole lot of moisture. I will make mention of this, although it is a pretty extreme scenario.. the 06z GFS shows this system diving very far south, and actually bringing a dusting of snow to north Florida Tuesday night! That would be pretty interesting if it happened.

Winter Storm **UPDATE**

Posted in Severe weather, Winter weather with tags , , , , , , , on January 31, 2009 by stormstream

I normally don’t post and evening update, but there has been so much concern over what the models are showing today in regards to the system for early next week, that I felt compelled to post some thoughts.

First off, and this needs to really be stressed and understood, the energy in the atmosphere that is going to be the catalyst for this storm hasn’t even made it to the lower 48 yet. It is still out over the data-void Pacific. So, until this energy makes it over the U.S. and can be sampled, the models are not going to be all that reliable. I am seeing people embracing various model runs like they are the be all, end all models for this storm that hasn’t even formed yet. I am perplexed and somewhat amused by this.

I am certainly not saying that the models should be ignored until the energy makes it to U.S. atmosphere. There are definitely some trends that can be noted and used as possible predictors of the future of this system. The most notable trend today has been for a weaker, non-phased system that tracks farther south than models were indicating yesterday. Given the current look of the mid and upper levels and what is happening upstream and downstream of the Southeast in the atmosphere, I’d say a weaker, non-phased system looks reasonable at this point. I am, however, having difficulty buying into the extreme southerly track shift indicated by the NAM, and especially the 18z GFS. Track is difficult enough to be forecasted by the models 24 hours in advance, let alone 72 hours prior. And track is something that really cannot be determined very accurately without the benefit of sound, real-time data, which this system does not have yet since it is still out over the Pacific ocean. So, a weaker system that is not phased takes the storm out of the major winter storm category and places it in the normal winter storm category. Still a winter storm that is sure to cause some problems across parts of the Southeast, but not one that goes down in the history books as a really memorable or historic event.

Until the system gets better sampled and a true and substantiated track forecast begins to emerge on the models later tomorrow into Sunday, I will not change my thinking on where the most significant snow will fall. I will still say that significant snow of 3 inches is possible across central and southern AR, northern MS, much of TN, northern AL, northern GA. South of that to the I-20/85 corridor, I will continue to go with a possible accumulation of a trace to as much as 3 inches. I am not so sure about the certainty of a major snowfall in the mountains of NC and TN, so right now I’ll revise my thinking downward on that into the 4 to 8 inch range, instead of the foot or more that had been my previous thinking.

Something else that has emerged on today’s models is the chance for a fast moving upper impulse zipping across the Southeast Tuesday afternoon through Wednesday morning. If this happens it would bring a burst of snow lasting about 6 hours. Given the air mass in place it would fall as all snow, and the ground would be cold, so there would be no initial melting. Also, ratios as high as 15 to 20 inches of snow to one inch of water equivalent could yield an inch or two or maybe even three of fluffy powder for those under the fast-moving area of snow. Definitely something to watch.

All in all I would just advise the snow hounds of the Southeast to remain calm and patient and wait until Saturday night or even Sunday before buying lock, stock and barrel into a forecast model solution, especially in regards to track of the storm.

Major Southeastern Winter Storm Still on Track, but Many Questions Remain

Posted in Severe weather, Winter weather with tags , , , , , , , , , , , , , , , , on January 30, 2009 by stormstream

As has been the case since about the middle of December, it is model madness today in regards to the major winter storm that will affect the Southeast next Sunday night through Wednesday.

The GFS is trending faster and weaker with the system. If this model were to verify then most areas between I-40 and I-20/85 would see a minor to modest snow event, with the southern Appalachian mountains making out pretty good, and areas north of I-40 doing ok. Nothing rip snortin’ as my friends in Texas would say, but still a nice little winter event.

Meanwhile, the 0z run of the ECMWF (European model) shows a classic Southeast snowstorm track with plenty of cold air in place to create a heavy swath of snow from Birmingham to just north of Atlanta to Raleigh. With a heavy dumping of snow in the southern Appalachian mountains.

Then you have the NAM, our high-resolution short range model that is showing the low pressure system also taking a favorable route for significant Southeast snow, but without the cold air that the GFS and ECMWF show. Thus, you end up with rain for much of the duration of the storm south of I-40, with a changeover to flurries and snow showers on the back side as colder air dumps in. Again, the southern Appalachians get a heavy dump of snow.

So, based on what the “Big Three” are showing today, one can conclude that there is a pretty good chance for a nice dumping of snow in the mountains of TN and NC, with potentially a foot or more adding up between Monday night and Wednesday evening. Monday night and Tuesday being synoptic snow, meaning snow with the system itself, then Tuesday afternoon through Wednesday being a prolonged period of northwest flow snow and snow showers behind the system that adds yet another 3 to 6 inches on top of the 4 to 8 inches that has already fallen. The ski resorts will be lovin’ it! This part of the forecast one can feel somewhat confident about. However….

For most of us in the Southeast who do not live in them thar hills, the snow forecast for Monday and Tuesday is still a very difficult one. Now it would be a lot easier if the forecast models had been performing consistently well this winter, but that is not the case. All of the big three, the GFS, NAM and even the ECMWF (statistically the most reliable medium range model) have been performing consistently poorly since about the middle of December. So, what we have to do is look at the performance of each one over the past 50 days or so, and try to draw some conclusions on which one is going to do the best based on past performance.

The GFS has tended to be too fast with moving systems in the 1 to 5 day range. This was very much the case with the last system – the ice storm. I feel that it is again too fast with the movement of the current system.

The ECMWF has been inconsistent this winter in the 6 and 7 day period, but it has performed much better than the GFS in the 1 to 5 day range. Therefore, I would tend to lean more toward following the ECMWF solution with this particular storm.

Finally, the NAM had not performed well at all as a short range forecast model up until this past storm. It did pretty well with the ice storm west of the Appalachians, and I regained some faith in this model again. However, with the system that will be developing this Sunday I feel it is under-forecasting the cold air. There is a decent snow and ice pack north of the Southeast region, and this is going to help with the southward penetration of cold air into the Southeast. Also, the NAM does not show much of a surface high pressure reflection across the northern Plains, the source of the cold air for our early next week storm. It has a 1034mb high over Idaho. Meanwhile, the GFS and ECMWF both snow a nice over 1030mb high pressure system seeding the cold air for the Southeast. I’d tend to buy the colder models over the warmer NAM at this point.

So, with all this said, my forecast for this system at this time follows closely what the ECMWF is showing in terms of surface low track and cold air, although I do feel the track of the low will be a bit more north and west of where the 0z ECMWF is forecasting it. I am also using the NAM as my forecast model of choice in regards to the speed of the system. This all translates into the potential for a swath of significant snow stretching from northwest MS middle TN, northern AL and north GA, and into western and central NC. The mountains of NC and TN will also see a heavy snowfall of a foot or more in some locations. By “northern AL and north GA” I’m talking about a line from Tupelo, MS to Cartersville, GA to Taccoa, GA. Still too early to pin down amounts in the potential swath of significant snow, but amounts could be over three inches. South of that more significant snow, I’d say accumulating snow will be possible along I-20/85 for cities like Birmingham, Atlanta and Raleigh. Again, it is too early to pin down a specific amount forecast so I’ll give a range of anywhere from a trace to 3 inches.

Finally, we cannot forget there will be a severe thunderstorm component to this storm. First for southeast TX and southern LA on Sunday, then along the Gulf coast of MS, AL and the Florida panhandle on Monday. Parts of extreme south GA and the Florida peninsula on Monday night. Then the eastern Carolina’s on Tuesday. Main threats will be damaging winds and some hail.

I just took a look at the 12z NAM, and here are some quick thoughts on that. First off, the NAM continues to show a slower speed with this system. I am even more confident now that the faster solutions shown by the GFS and ECMWF are less likely to verify than the slower NAM. So, I think the NAM is definitely onto something in regards to speed. Next, the 12z NAM is snowing the surface low tracking across the Gulf of Mexico, well south of the coast. This has resulted in a deeper southward penetration of the cold air, so the 12z NAM is definitely colder than its predecessor. Based on what I am seeing, I’d still say a swath of significant snow is possible for much of central and southern AR, northern MS, northern AL, much of TN and western and central NC. Maybe not so much of a dumping for the mountains of TN and NC if the low tracks that far south. I still buy the ECMWF track of the surface low more than I buy into the southern track depicted by the NAM. It’ll be interesting to see what the 12z ECMWF shows.

Bottom line: Still more questions than answers, but we are definitely starting to get some answers now, and more will come into focus later today and especially tomorrow, so stay tuned!!

Major Winter storm WILL Impact Parts of the Southeast Next Monday and Tuesday

Posted in Winter weather with tags , , , , , , , , , , , , , , , , , , , , on January 29, 2009 by stormstream

I normally do not make such a declarative statement so many days in advance of a weather system, but based on my thoughts on how the weather pattern would evolve all month, and based on overwhelming model support, I feel 100% confident in saying a high-impact winter storm will affect parts of the southeast on Monday, February 2 and Tuesday, February 3, with the worst of the storm happening in the noon Monday to 6am Tuesday time frame based on current models.

Of course nothing is set in stone with this system, and much can change between now and Monday.  The most likely things to change would be the strength and track of the surface low pressure system.  These changes, even if slight, can and will translate into major changes in the forecast since the synoptic heavy snows associated with the low pressure system are likely to be confined to a rather narrow corridor.  So, pinning down exactly where the heavy snow will set up this early in the game simply cannot be done with any kind of accuracy.  Sure, someone could throw a forecast out there, and they could very well get lucky and have it verify, but it would truly be a case of “skilled luck” as I call it.

In general terms, the areas that are most likely to see snow Monday would be northern MS, western and middle TN, northern AL and northwest GA.  On Monday night and Tuesday morning the snow would affect the remainder of north GA, the upstate of SC, eastern TN and western and central NC.  The central and northern mountains of TN and NC look particularly interesting as they could see a burst of heavy synoptic snow early Tuesday morning, then a prolonged northwest flow upslope event that lasts from Tuesday morning to Thursday morning that will add to their snow depth.  The ski resorts will be loving it by next weekend.

Finally, there will likely be a severe thunderstorm component to this system.  A severe squall line with damaging winds being the main threat could sweep across southeast AL, southern GA and much of FL Monday afternoon through Tuesday morning.  Depending on the track of the surface low, central and eastern South Carolina and eastern North Carolina could get in on some severe storm activity as well.

Many more finer details regarding this storm will come into focus this weekend, so keep checking in for my latest thoughts on this major system.

Major Southeastern Winter Storm Early Next Week?

Posted in Winter weather on January 28, 2009 by stormstream

Well, the biggest and most widespread winter storm of the season is winding down today and tonight.  Parts of northeast AR, southeast MO, northwest TN and western KY were absolutely crushed by a major ice storm.  There is a lot of tree and property damage around this region, and it will be years before the trees recover and look full again.  Ice storms are really sad events in terms of the damage they do to property, as well as the trees.

Now we look to the next potential winter storm for the Southeast, and that is being forecasted by the models for next Monday and Tuesday (Feb. 2 and 3).  I guess we can call it the “Groundhog Storm of 2009″ if it comes to pass.  We have to be very careful buying onto any forecast model at this piont.  It was this time last week that the models were showing either a major winter storm or severe weather maker for the Southeast for the end of this week.  Neither of which is going to happen.  However, I do feel the models are now finally adjusting to the pattern evolution that has been underway for the past four weeks, and are now starting to come around in their ability to accurately forecast the state of the atmosphere in the 3 to 6 day range.  Even the NAM, which has not been a very reliable short-range model this month, did a decent job forecasting the current ice and snow storm.  So, I am mildly optimistic that the GFS, ECMWF and the ensembles may actually be on to something for early next week.  Plus, all month I’ve been forecasting a major winter storm to impact the Southeast along and north of I-20 and I-85 at the end of January or very early in February.  This MAY be my storm.  We’ll see.

It is still way too early to talk specifics, but IF this storm were to happen, there is a chance for significant snow impacting northern AL, north GA southeast TN, the upstate of SC and western and central NC.  This would appear to be more of a wet snow threat than an ice threat at this time, and temperatures will be very boarderline at the time most of the more significant, deep moisture is over the region.  It could very well end up trending toward yet another situation where the good moisture scoots out before the cold air moves in.  We’ll see.  At least we have something interesting to watch, and my gut tells me this will not be a system that the models taketh away, but one that remains intact, but shifts track a few times between now and the weekend.

This entry was posted on January 28, 2009 at 3:11 pm and is file

Major Ice Storm This Week, with Significant Snow North of the Ice

Posted in Winter weather on January 25, 2009 by stormstream

A long duration winter storm will impact areas from the eastern Plains to the TN and OH Valley between Monday and Wednesday of this week.

A major ice storm could impact areas from southeast KS and northeast OK, eastward across southern MO, northern AR, extreme northwest TN, much of KY and into parts of VA.  North of that zone of significant ice will be a zone of significant snowfall.  This has the potential of being the most far reaching high-impact winter storm of the season.

Then, yet another high-impact winter storm is being depicted by the operational GFS model for this Friday and Saturday.  This one is being shown affecting parts of the Southeast, Mid-atlantic and Northeast.  I have my doubts about this ending up being a true threat due to the poor performance of the GFS beyond five days this winter, however, it does lend some validity to my thoughts all this month that a major winter storm could impact parts of the Southeast in the final days of January, or very early in February.  So, I’m at least willing to give the GFS some measure of love on this until it takes the system away later today or tomorrow, then I am back to hating on it.

My disgust about the operational GFS this winter is only in the forecast range beyond about four days.  I actually think it has performed rather well in the one-to-three day range, and in fact, has beaten the NAM on several occasions.

Active Weather Pattern – Three Storms Possible Over the Next Two Weeks

Posted in Winter weather on January 21, 2009 by stormstream

Looking into my crystal ball of medium range forecasting I see a lot of potential, and I mean a lot.  Then again, there has been a lot of potential most of the winter so far, and for the most part it has been wasted here in the Southeast.  So, we’ll see I suppose.

All month I’ve been thinking we would eventually see a high-impact winter storm across parts of the Southeast arising out of this generally cold weather pattern we’ve been in for several weeks.  The medium range models are showing the potential for a sleet or freezing rain system for mainly North Carolina on Sunday.  Then a much bigger storm, either rain or snow, possibly heavy, toward the end of the next work week.  Then yet another major storm around the 3rd or 4th of February that could be either a severe thunderstorm producer, or major snow and ice producer, or both.  So, the models do show a lot of potential, but the details have yet to be worked out.

I’ll be watching both the Plains and Southeast with great interest over the next few weeks, as both areas are targets for possible chases.