East Coast Winter Storm Expected To Develop This Weekend

Expected Temperature Departures For Saturday

Over the past couple of weeks, the forecast models have been in complete limbo. Even the European model, which is usually the model of choice for medium-range to long-range forecasting, has been all over the place in recent weeks. Initially, models had ridging building over the eastern United States to kick off November, which would have brought the area above average temperatures, but things made an 180 degree flip just a few days afterwards. I say that to point out that the atmosphere is acting in a way that has been difficult for models to handle, and it is showing in their outputs. I can’t say that I’m surprised, but that makes forecasting extra tricky. Once we get into the swing of winter, hopefully everything will get better. If you followed my forecasts at all last winter, you know that it’s common for me to disagree with forecast models especially in the medium and long-range.

What To Expect This Weekend: 

There is a trough that is going to develop and strength as it digs south over the eastern United States. A mid-level shortwave trough is then going to push south late this week and eventually close off as it makes it way to the Carolinas by this weekend. There is a strong model consensus that a surface low is going to develop over the Carolinas, and then strengthen off the Carolina coast. Now, don’t worry if you don’t understand any of the meteorology behind this.

Basically, this amplified trough is going to bring cold air with it. Areas such as the Great Lakes, the Ohio River Valley, the Tennessee Valley, the Southern Plains, the Southeast, and the East Coast will be experiencing the coldest air of the season so far this year. This is an impressive system for this time of year, although it’s not necessarily unprecedented. Places even into the panhandle of Florida will have temperatures dipping down into the 30s. You can expect areas further to the South experiencing their first freeze of the season this weekend. Strong winds can also be expected with this system, particularly in the mountains.

Expected Temperature Departures For Saturday

Expected Temperature Departures For Saturday

This will give you a taste of what I am expecting to come this winter. The weather across the United States will be volatile in November, meaning I don’t expect a cold pattern to set in for a long period of time for any particular region early on. I do expect wild swings in temperatures throughout the month, but I will discuss more about that in a few days.

What To Expect With This Winter Storm: 

Because there is a strong model consensus on the track of the upper-level feature that will be pushing south, it is hard for me to disagree with the overall track and where the surface low will develop. However, if for some reason the upper level low does not go as far south as forecast models are projecting, then we have a much bigger East Coast winter storm on our hands. At this point, I’m not ruling that possibility out.

Because the upper-level low is expected to push further south, the surface low pressure will be developing further south and eventually deepening along the Carolina coast. Now, the track of this system is key. If the current model projections verify, then this storm would produce a fairly decent snow event in the mountains, and amazingly, models even have enough cold air rushing in that there could be some wet snowflakes or snow showers outside of the mountains, possibly in the Charlotte area and even into northern South Carolina. Places even as far south as the southern Appalachians could get some snow.

Latest NAM Shows A Decent Snowfall Event In The Mountains

Latest NAM Shows A Decent Snowfall Event In The Mountains

Since this upper-level low is projected to go so far to the south, the surface low would stay far enough off the coast once it starts moving northward to prevent a major East Coast winter storm from taking place. Could this upper-level feature not go as far south? It’s possible, and future model runs need to be monitored just in case that were to occur. We would be dealing with a much bigger event along the East Coast if that were to happen.

Regardless, the mountains will most likely get their first big northwest-flow snow event, and places up in the Ohio Valley could see some snow. This low pressure eventually will move along the Northeast coast later in the weekend, and places like eastern Maine could get some pretty heavy snow.

So basically, storm track is pretty much everything. The cold air seems like it will be sufficient to support a winter storm, but how everything evolves will determine who gets what and how much. I always have a hard time trusting the forecast models particularly this time of year when we are entering the winter months and are in a transition phase. I always like to see how the models handle these pre-season storms.

Follow Firsthand Weather on Facebook: 

I will be posting future updates on any changes regarding the weekend winter storm on Facebook, so be sure to like the page if you haven’t already. If there were to be any significant changes, I will be posting a follow-up article, but otherwise, I will be working on Firsthand Weather’s final 2014-15 winter forecast that will be coming out this Sunday, November 2nd at 2 pm ET.

Siberian Snow Cover May Bring A Brutally Cold 2014-15 Winter

Siberian Snow Cover

Over the past several years, I have put out numerous early and final winter forecasts for the United States with some of them being spot on and some of them not. When doing my research for the upcoming winter, I always come across countless winter forecasts that have been put out by amateur and professional weather forecasters, and it doesn’t matter how much experience a weather forecaster has, the majority of winter forecasts end up being wrong.

Do Meteorologists Weigh Too Heavily On El Niño and La Niña?

The one thing that I have noticed over the last five years is that forecasters weigh too heavily on one variable: ENSO (El Niño/La Niña). Now don’t take that the wrong way! El Niño and La Niña can have huge impacts on the winter months in the mid-latitudes (United States winter), but there are MANY other variables to consider. Like you’ve heard me say many times, the strength of El Niño/La Niña and the placement of the warmer/cooler waters across the central and eastern Pacific can be a determining factor as to how heavily ENSO needs to be considered for that upcoming winter in the United States.

Most of you have heard of the NAO (North Atlantic Oscillation) and the AO (Arctic Oscillation). It’s something you hear more about during the winter months, and these are two indices that can heavily impact temperatures and precipitation each winter across the United States. NAO/AO are often considered by most meteorologists and long-range forecasters as wildcard factors, and something that can’t be accurately predicted beyond a 1 to 2 week period. If you’re relying entirely on forecast models to make that prediction for you, then that statement is generally true.

Can Siberian Snow Cover In October Be An Accurate Predictor of the United States Winter?

Since around 2009 or 2010, I have been following the work of Dr. Judah Cohen, the director of seasonal forecasting at Atmospheric and Environmental Research (AER). Dr. Cohen has numerous peer-reviewed publications on the impact that Siberian snow cover has on the upcoming winter months (December, January, and February), and his research shows that the rapid extent of snow cover over Siberia in October can impact the phase of the NAO/AO for that winter.

Snow Forced Cold Signal. Courtesy Judah Cohen - MIT

Snow Forced Cold Signal. Courtesy Judah Cohen – MIT

With that said, one must realize that the Siberian snow cover extent in October alone can’t accurately predict the upcoming winter temperatures across the eastern United States. When you just consider the snow cover extent, only evaluate the monthly value, and include all of Eurasia, the correlation between snow cover and the winter AO is not as strong. Notice the correlation coefficient on the graphic below is 0.41 (a correlation coefficient of 1 would be perfect positive linear correlation).

October Siberia Snow Cover Extent and Winter AO Correlation. Courtesy Dr. Judah Cohen - MIT

October Siberia Snow Cover Extent and Winter AO Correlation. Courtesy Dr. Judah Cohen – MIT

Dr. Cohen and his team have come up with an index called the Snow Advance Index (SAI). The SAI uses daily (instead of monthly) values of snow cover extent over the entire month of October and only considers the region south of 60 degrees north. Notice how the correlation coefficient is nearly 0.86, which shows a strong correlation between the SAI index and the winter AO. This index shows that the rate of snow cover change over this region has a bigger impact on the winter temperatures across the United States vs. the snow cover extent by itself. The negative values on the graphic below would indicate a snowier and colder winter in the eastern United States.

October SAI and Winter AO Correlation. Courtesy Judah Cohen - MIT

October SAI and Winter AO Correlation. Courtesy Judah Cohen – MIT

 

So How Is Everything Looking For the 2014-15 Winter? 

Siberian snow cover is already rapidly expanding, and based on forecast model guidance, that trend is going to continue throughout the rest of the month. Because the SAI considers daily snow extent values, Cohen and his team will not make any predictions until after this month is over. Remember how cold the 2013-14 winter was?? Well, October 2013 had the 4th highest snow cover extent over Eurasia (Siberia) since 46 years of records began. As of October 13, 2014, 12.2 million square kilometers of Eurasia were covered by snow compared to 10.8 million square kilometers around this same time last year. We’re already way ahead of what even occurred last year!

Map Showing Snow Cover Extent Over Siberia as of October 14th, 2014.

Map Showing Snow Cover Extent Over Siberia as of October 14th, 2014.

October 1976 holds the record as having the highest Eurasia snow extent of 17.2 million square kilometers! We all have heard about or remember the notoriously cold 1976-77 winter that broke countless records. In recent years, the 2009-10 and 2010-11 United States winters were heavily impacted by the negative phases of the NAO/AO, which caused bitter cold across a large chunk of the U.S and numerous East Coast winter storms.

We could be heading down that same road again this winter, but we still have two more weeks to go in October. A lot can change in two weeks, but as I stated above, model guidance suggests that this snowy trend over Siberia is going to continue.

GFS model shows snow depth and snow extent increasing in the coming days.

GFS model shows snow depth and snow extent increasing in the coming days.

 

What’s Next? 

I am planning to release my final 2014-15 winter forecast on November 2nd! Before that forecasts comes out, I am going to do a “part 2” of this article explaining exactly how Siberian snow cover expansion can lead to a negative NAO/AO winter, and therefore, bring with it a brutally cold and snowy winter for the eastern United States. Please understand that Siberian snow cover is only one variable that I consider when putting together my final winter forecast.

Please be sure to like the Firsthand Weather Facebook page, where I plan to keep everyone updated on whether or not the Siberian snow cover continues to rapidly expand the second half of this month!

Hurricane Gonzalo Heading Straight For Bermuda

Hurricane Gonzalo

Hurricane Gonzalo has rapidly intensified into a major hurricane with sustained winds currently around 115 mph, and pressure is down to 970 mb. Latest recon data shows that this storm has rapidly intensified over the last few hours so the pressure has likely dropped and the winds have increased since the last advisory at 5 pm ET. Gonzalo will continue to head northwest before turning north and eventually northeast towards Bermuda. Bermuda was recently impacted by Fay, and Hurricane Gonzalo could even be a bigger blow to the island.

Hurricane Gonzalo Projected Path

Hurricane Gonzalo Projected Path

Right now, there is nothing that is stopping Gonzalo from rapidly intensifying since it is not currently being negatively impacted by shear, and the sea surface temperatures are warm enough to promote further strengthening. The strong upper-level trough that is currently moving across the United States will keep Gonzalo from hitting the United States and will be responsible for making the storm take a northeast turn. This is the same trough that was responsible for the severe weather across the United States this week.

Hurricane Gonzalo Intensity Forecast

Hurricane Gonzalo Intensity Forecast

As Gonzalo moves further north, it could be impacted by some shear (that may or may not cause the storm to weaken), and the waters up towards Bermuda will be several degrees cooler. There is the possibility that this could cause the storm to weaken some, but still, this storm will still likely be a damaging hurricane. If you live or have friends and family in Bermuda, make sure prepare for this potential impacts of this storm. Gonzalo is expected to hit or come close to Bermuda on Friday.

We’ll continue to keep a close watch on everything at Firsthand Weather, and be sure to follow us on Facebook for the latest updates on this powerful hurricane.

Weekly Forecast: Tornadoes, Flooding, and Damaging Winds

SPC's convective outlook for Tuesday.

I have not done a weekly forecast like this in a long time, but since many of you have expressed interest in reading a weekly forecast, I have decided to do one. Please understand that these forecasts will improve over time, and I apologize in advance if I did not cover your area in this first outlook. It’s hard for one forecaster to cover the entire United States, but I did my best to hit the high points.

Short-range Forecast (Sunday evening through Wednesday morning): 

Sunday evening: A strong mid and upper-level trough will be moving from the Rockies and pushing south into the Southern Plains by tonight. At the surface, a low pressure system is going to continue to strengthen as it moves east over the Southern Plains tonight and will eventually move northeastward from the Southern Plains tomorrow. Storms should really begin to fire later this afternoon and early evening over the Oklahoma and Texas panhandles and continue to develop and push eastward ahead of the associated cold front into Oklahoma and northern Texas and eventually Arkansas into the late evening/early morning hours, which will continue through the morning hours.

There is going to be a window of opportunity for isolated tornadoes to develop later tonight going into the early morning hours in northern Texas including the Dallas area, portions of eastern Oklahoma, and extreme western portions of Arkansas. Especially if discrete storms develop ahead of the main area of convection, this could lead to some trouble, so this needs to be watched. The severe weather threats that I am more confident will occur are flooding and damaging winds. Flood watches have already been issued for portions of eastern Oklahoma, southeastern Kansas, and western Arkansas, since these areas could get several inches of rain in a short amount of time. Even regions around the watch area need to also monitor the flooding situation.

Projected radar for early Monday morning from the HRRR model.

Projected radar for early Monday morning from the HRRR model.

Monday and Monday evening: As the surface low pressure system moves northeast and the trough becomes more amplified and moves eastward, the severe weather threat will continue to be a problem on Monday and Tuesday out ahead of the associated cold front. I’m currently keeping a close watch on the lower and mid Mississippi River Valley region, where environmental conditions could become favorable for tornadoes. Although CAPE values (instability) will not be impressively high, high deep-level wind shear will be plenty sufficient with this system to produce an environment that is favorable for discrete supercells to develop and produce tornadoes. In fact, a couple of these tornadoes may be strong. The Storm Prediction Center is considering upgrading some regions to a moderate risk in their next outlook. The region that really needs to watch the tornado threat on Monday will be eastern Arkansas, northern Louisiana, northern half of Mississippi, western Tennessee, and southeastern Missouri. Please note that tornadoes will not be the only threat, but that damaging winds will also be a big threat as a squall line will likely move through all of the mentioned regions.

Flooding will also be an issue in many of these regions on Monday, including Arkansas, Mississippi, Alabama, Tennessee, and Kentucky, and flood watches could definitely be issued for many of these areas later on.

SPC's latest convective outlook for Monday.

SPC’s latest convective outlook for Monday.

Tuesday and Tuesday evening: Tuesday gets a little more difficult to forecast, and I’ll explain why. The mid and upper level system will continue to race eastward, pushing the severe weather threat into eastern Alabama, Georgia, Florida panhandle, Upstate and Midlands South Carolina, eastern Tennessee, and western portions of North Carolina. Most of these regions will likely experience strong winds due the a squall line that will be pushing through the area. Where things get a little more uncertain is the tornado threat, and because I feel that there could at least be isolated tornadoes on Tuesday, I wanted to mention it so that you all aren’t caught off guard if this occurs. This is an example of a low CAPE/high shear setup, meaning that the environment may not be particularly unstable but the high shear environment may compensate for the lack of instability. I have seen cases where this region can get several tornado touchdowns due to this kind of setup, and the people living there be caught off-guard by it. I would not even be surprised if a tornado or two occurred within the squall line of storms that moves through the area. So the area I am watching most closely is Georgia, Upstate South Carolina, and the Southern Appalachians. It could really go either way, so I just wanted to mention it.

Even if no tornadoes occur that day, the damaging wind and flooding threat will be in place over most of these areas. Flooding rains is a danger that is often overlooked by forecasters and the general public.

SPC's latest convective outlook for Tuesday.

SPC’s latest convective outlook for Tuesday.

Conclusion: I’m going to go ahead and end this article since it is already getting a little long. Again, I know that there are regions that I left out that I will try to include in future weekly forecasts. This weekly outlook was completely about the expected severe weather, but on weeks when we don’t have any big weather events occurring, I should be able to extend this outlook to 5 to 7 days and cover more regions.

Please share this article to indicate to me that you want similar forecasts in the future. Please also let me know anything that you want me to include in these forecasts and any changes that you would like me to make. Be sure to sign up for my newsletter that will start up again this winter (over 3,000 of the 5,000 slots are already full), and be sure to like the Firsthand Weather Facebook page!