Dec 09
December so far has been a battle between the cold northern tier and warmth south. The so-called “battle zone” has been located over our neck of the woods and lead…
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Dec 16
During the late summer and early autumn months we were trying to look at the big picture and potential drivers in the overall weather pattern for the upcoming winter and openly admitted the challenges that were ahead. Here we are now into the second half of December and a much colder and snowier-than-average month is a virtual lock at this point. Furthermore, consider this has all taken place without the presence of a favorable NAO or PNA. Sometimes you have to look for other drivers in a pattern- in this case, the EPO, as well as a growing early fall snow pack across the border to our north. Additionally, we made mention of the likelihood of a southeast US ridge periodically making itself known through the winter of ’13-’14. You can read all of our thoughts posted earlier this fall here, or by clicking the Thoughts On Winter ’13-’14 page above.
As we look ahead towards the upcoming wintry challenge, we’re confident of the overall pattern, but the sensible weather that’ll ensue is still up for great debate. “Gut” tells me central Indiana will be looking at a rain to freezing rain scenario, but this is far from set in stone, and sometimes forecasters who go simply off their instinct can get burned. The pattern is one that (once again) will feature a pressing arctic front against resistance from the southeast US ridge. With this type of scenario, I would advise against looking at each and every individual operational model run, but instead invest time studying the ensembles- an average of several multiple model runs as opposed to just one operational model run. I can guarantee a variety of wild solutions ahead in the days to come, based off the operational runs. (Heck, just the past 24 hours have been reason enough to have the dramamine on hand :-)). That said, let’s take a look at the latest GFS and European ensembles, two models that we rely heavily on in the mid range weather pattern.
First, the GFS, valid Saturday through Monday.
Now, here’s a look at the latest European ensembles (left), again valid Saturday-Monday.
So what do all of these cool maps tell us? Simply put, that “wintry mischief” is brewing for the weekend. That much we know, but the details have to be ironed out. It’s likely heavy snow and a significant ice storm looms for some of the Mid West and Ohio Valley for the upcoming weekend. Is that Indianapolis or Chicago? Perhaps in between? It’s too early to know. Additionally, in the “warmer” sector, heavy rains are likely to combine with an impressive early season snow pack for some to lead to flooding concerns.
A couple of additional items to note. Many times at this stage in the game (still 5+ days out) with this type of pattern, forecast models really struggle with handling low level cold air. Cold air is very dense and, in this type of set up, can easily drain much further east and south than forecast at this juncture. Additionally, sometimes the modeling can put too much “umph” into the associated surface wave that moves along the arctic front resulting in a further north track than what may actually occur when the event draws closer. Just something to keep an eye on as we draw closer…
Needless to say, it’ll be particularly important to keep a close eye on the developing weekend forecast as we move forward. It’s likely folks in the Ohio Valley region have to deal with significant precipitation amounts in the Saturday-Monday time period, including rain, freezing rain, and snow.
Permanent link to this article: https://indywx.com/major-storm-brewing-this-weekend-but-details-are-murky/
Nov 24
As we approach the all-important holiday travel season, I thought it would be nice to review what some of the data suggests in the long range sense. While nothing is “set in stone” talking about weather 2-3 weeks out, we feel pretty confident in the overall idea of a colder than normal pattern and one that’s also potentially wintry- from a precipitation perspective. The specifics with each storm will have to be handled as they come.
Let’s look at some of the data. BTW, I want to give full credit to the awesome model suite that can be found at Weatherbell Analytics for some of these images. Be sure to check them out at weather bell.com.
First, we’ll take a look at the Canadian ensembles, centered on the 8-16 day period. Note the tongue of cold coming out of western Canada, extending southeast and encompassing the Ohio Valley region. Folks, this is significant cold forecast off the Canadian ensembles as temperatures are suggested to average 5-7 degrees (C) below normal.
The latest GFS ensembles also suggest widespread colder than normal temperatures over the upcoming couple weeks. Similar to the Canadian (above), the GFS suggests temperatures average 5-7 degrees celsius below normal.
Latest European ensemble data suggests a cold look as well, but one that also may feature a day or two above normal (over the next couple weeks). The latest ensemble control run highlights the threat of some bitterly cold arctic air plunging south towards the second week of December (posted below). We’ll continue to monitor this in the days to come.
Here’s a look at the latest CFSv2. While it’s in stark contrast to only a couple of weeks ago (in its December forecast), the model is now onboard with most other data in forecasting a colder than normal December for our region.
It has to be pointed out that all of the cold data is forecast during a time where the three “major” teleconnections really aren’t in the most ideal spots for eastern cold. Typically, cold lovers across the eastern United States want a negative AO and NAO with a positive PNA. The NAO and AO are forecast to be very “sporadic” over the course of the upcoming 7-10 days while the PNA is forecast to go back negative. That said, the NAO has the biggest influence on our weather from January through March (we’ve covered this in posts in the archives). The expansive early season snow and ice pack through western Canada is having it’s say with a couple of early season “brutal” cold shots here (it’s very rare to get this kind of cold so early in the season). We’ll continue to monitor these teleconnections moving forward for any sort of a more defined signal that may begin to come to fruition.
Speaking of snow and ice cover; look at how much more territory across the Lower 48 is covered with snow and ice compared to this date (November 24th) last year. Impressive, huh?
November 24, 2012 (11.8% covered in snow)
November 24, 2013 (37.8% covered in snow)
As we look closer at the near term, there’s a chance of some light snow moving in Monday evening (not a huge deal, but some light accumulations of a dusting to half an inch are possible). Scattered snow showers will also blow into central Indiana Wednesday as a reinforcing shot of fresh arctic air blows in prior to Thanksgiving.
In the mid range, both the GFS and European ensembles (below) suggest an “intriguing” look for the first 10 days of December for the potential of a more widespread winter weather maker. It’s far too early for details, but with arctic air being supplied into a pattern that looks to have a southern branch beginning to flex it’s muscle, we’ll have to remain on our toes as we go into December… Here’s wishing you a very happy and healthy Thanksgiving, complete with safe travels!
Permanent link to this article: https://indywx.com/data-suggests-cold-pattern-keeps-on-keepin-on/
Nov 12
As we progress into the second half of November and December, friends and family begin to hit the road for holiday travel. It’s also at this time where winter weather enthusiasts begin to wonder when that first “true winter storm” will arrive. As we look towards this period, it becomes more important to note the state of the “big three” teleconnections. These include the PNA (Pacific North America pattern), NAO (North Atlantic Oscillation), and AO (Arctic Oscillation). While it’s impossible to predict, with 100% certainty, the weather based solely off these teleconnections, they can be very good indicators of where the pattern may be heading in the next couple three weeks.
In a “perfect world” for those wanting cold and wintry weather here across the Hoosier state you want to see a positive PNA, which promotes western ridging and eastern troughiness (associated with cold weather). Additionally, you want to see a negative AO and NAO (promotes high latitude blocking and corresponding cold, arctic, air is shunted south into the Lower 48). What do the teleconnections currently show?
Taken at face value, this suggests a cold and potentially wintry pattern may ensue to close out November and as we go into December. We’re looking at an AO and NAO trending negative and a PNA trending positive. *It should be noted that, at times, a negative NAO can be so strong that it supplies the cold air, but can also lead to a suppressed storm track- south of the available cold air…
Each storm provides it’s own set of challenges and must be dealt with as they come. We can look at past storms and patterns (called analog forecasting) to help get an “idea” as to what patterns and storms in front of us may produce, but no storm is identical to the other. At this early stage in the game, it appears as if a pattern is setting up that could provide “wintry mischief” just at the time when most folks want it- for the Thanksgiving and Christmas season.
Stay tuned…
Permanent link to this article: https://indywx.com/pattern-showing-signs-of-more-sustained-wintry-weather/
Oct 21
Right on cue, the well advertised cold pattern is settling in and looks to remain entrenched over the region to close October and open November. Note the eastern trough and…
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