December 2013 archive

Dec 23

Impressive Cold Pattern Looming; Beware Of The Northwest Flow…

We continue to be very impressed with the cold pattern that’s looming.  Even before the warm up and thaw last week, we made mention that the seeds were being planted for a very cold close to December and open to 2014.  Latest data continues to back this idea up.  Additionally, in the longer term, there are some goings on that would suggest we better hunker down for a colder than average January.  While December will finished colder than average, a colder than average January can really hurt the pocket book as “average” temperatures are obviously even colder than December.

Today’s 12z ensembles are locking in on the pattern than can deliver one shot after the other of arctic air in the 8-10 day range.

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As for the snow, we still think we need to watch the models around the New Year for the threat of some southern stream energy interacting with the available cold air.  That said, even without the southern stream, one must remain abreast of the challenge that a northwest flow pattern can produce.

Forecast models have a difficult time handling clipper systems in these type of patterns until within 24-48 hours within an event.  Many times what appears to be a rather “harmless” clipper 4-7 days out can suddenly turn much more robust once the model catches onto the track and ability to literally squeeze out any and all available moisture from a cold air mass.  Furthermore, the “normal” 10:1 snow ratio, many like to use, doesn’t apply in the least to these type systems.  In cold environments you can easily get what’s called the “fluff effect” and snow ratios are more in the 20-30:1 range.  Needless to say, it’s a challenging pattern that will keep us on our toes over the coming couple of weeks.

To summarize, we’re extremely confident on a colder than average close to December and open to January.  We’ll have to monitor fast moving clipper systems that modeling will struggle with until right up to the event.  Finally, we’ll keep a close eye on the potential interaction of the southern stream and cold air around the New Year time period for the possibility of a storm of “more significance.” Stay tuned!

Permanent link to this article: https://indywx.com/2013/12/23/impressive-cold-pattern-looming-beware-of-the-northwest-flow/

Dec 21

Dangerous Flood Event Developing

Widespread rainfall totals are approaching 1″-2″ since the rain begin Friday across central Indiana.  When you look at the big-scale radar picture (snapped shortly after 8 o’clock this morning), you can understand the concern that’s ahead later this evening into Sunday, from a flooding perspective.

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Latest projected rainfall numbers remain very consistent on the message we’ve been passing off  to you, the viewer, for a few days now…widespread 3″-4″ totals, with locally heavier amounts.

We think steady moderate to heavy rains continue for the better part of the day, but we note our short term, high-resolution, models targeting this afternoon and overnight for some extreme rainfall rates to develop.  Here’s a look at the simulated radar valid 7pm this evening:

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When you consider the snow melt and the rain that will have already fallen by this point, the stage is set for a very dangerous overnight flooding situation.  Flooding any time of the day is dangerous, but particularly so at night.  If you live in a flood prone area, PLEASE make sure to have a plan in place and consider perhaps spending the night with family or friends tonight as rapid water rise is certain to occur.

Permanent link to this article: https://indywx.com/2013/12/21/dangerous-flood-event-developing/

Dec 20

Colder Than Normal Pattern Set To Return

Before we go into the cold pattern that is looming, our current forecast of severe flooding developing across central Indiana this weekend remains.  Our projected precipitation numbers remain in the 3-4″ range for most of central Indiana, but there will be some higher totals reported.  Combine that with the recent snow melt and the stage is set for potentially a severe and dangerous flooding event.

As we look ahead to the next weather “challenge,” it has to do with temperatures.  As we’ve talked about in previous posts, our weather pattern flipped to one that has been predominantly colder than normal back in the middle of October.  Despite a handful of days, cold has dominated the pattern.  Before our current thaw temperatures were averaging 5 degrees below normal for the month of December.  While the recent thaw is certain to reduce the anomalous cold, the last week of December could send us right back to readings much colder than average, helping put the exclamation point on the month as far as cold goes.

The latest 8-10 day ensemble plots showcase a very cold pattern to end December.  Cross polar flow gets involved, helping lead to some bitterly cold air around these parts.  We note excellent agreement between the GFS and European forecast models, helping to further increase our confidence in the cold pattern ahead.

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But it doesn’t stop there…  We note long range data suggesting this cold pattern continues well into January.

The latest European forecast ensembles showcase the cold continuing to reload into the first week of the month.  This is an impressively cold look, considering we’re still a couple weeks out and that these are a multitude of individual computer model runs averaged together to come up with this solution.

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As we watch the evolution of the cold pattern, it’s important to turn to the “goings-on” with the upper air pattern.  Note the reorganization of the polar vortex and, equally as important, the placement of the polar vortex.  For the purpose of giving you a couple of different viewpoints of the evolution of the pattern we’ve pasted a Northern Hemisphere and North America perspective.

Note how the polar vortex reorganizes itself and decides to set up shop over Hudson Bay and Baffin Island by early January.  This is significant in that it promotes multiple reinforcing shots of arctic air into the eastern half of the country and backs up what the data above would suggest in the cold pattern that appears to be looming as we move forward…

Sunday, December 22nd

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Friday, January 3rd

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What does all of this mean?  That the current “thaw” is very brief.  The seeds were being planted for a return of the cold pattern earlier this week and it all begins Sunday night.  As the data above would suggest, the arctic cold appears to reinforce itself as we go through time and an overall prolonged colder than normal pattern appears to be setting itself up.

Additionally, we’ll have to handle winter storm systems as they come (and they will), but the pattern is one that very well may promote fast-moving clipper systems moving southeast out of Canada.  While most of these clipper systems don’t drop tremendous snowfall totals, the more potent clippers can deposit several inches of snow and serve to “feed back” and turn what’s initially a cold, dry pattern into one that’s suddenly snowy.  We’ll keep an eye on that.  Furthermore, the southern stream may also decide to add a little “excitement” into our forecast late December or early January.

Needless to say, there’s a lot of weather to talk about in the days ahead…

Permanent link to this article: https://indywx.com/2013/12/20/colder-than-normal-pattern-set-to-return/

Dec 20

Model Data Not Backing Down On Flooding Rains Ahead

A scan over multiple computer models this morning shows that forecast models remain consistent of the idea of a weekend deluge across central Indiana.  Unfortunately, when combined with the snow melt, if even the numbers are half right, we’ll have to deal with significant flooding this weekend, especially Saturday afternoon through Sunday.

Here’s a look at the data.  We average multiple computer models together to come up with our precipitation forecasts (both rain and snow) that you see in our daily 7-Day Video Forecasts (available to the right of this post).

CAN1EC1gfs_total_precip_east_11hires_ptype_acc_indy_20NAM1plotter

Needless to say, when looking over all of the data above, we still feel confident in the forecast we have out…widespread 3-4″ rainfall with locally heavier totals.  Preparations should have already begun if you live, or work, in a flood prone area, but if not, please do so today.  The question remains not if we’ll see flooding, but how severe the flooding will be.

Permanent link to this article: https://indywx.com/2013/12/20/model-data-not-backing-down-on-flooding-rains-ahead/

Dec 19

Thursday Morning Weather Rambles

As always, your latest 7-Day Video Forecast can be found to the right in the video player.   1.) A milder southerly air flow allowed us to remain above freezing…

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Permanent link to this article: https://indywx.com/2013/12/19/thursday-morning-weather-rambles/

Dec 18

A Lot Of Weather To Talk About…

Mother Nature seems determined to put us weather forecasters to hard work as we get set to head into the Christmas season and welcome in 2014.  We’re tracking a major flood situation that will unfold across central Indiana over the upcoming weekend, followed by a reload of the cold and potentially a storm with a more wintry component as we get closer to the New Year.

First things first and that’s the significant flood threat in the short-term period.  Without trying to go into scare tactic mode, current model data would result in a downright dangerous flooding event for many low lying and flood prone areas this weekend.  Rainfall numbers are extremely impressive with this event and with a deep tropical connection, widespread 3-4″ totals are certainly likely, including some localized higher amounts.  Note the latest European chart, courtesy of the model suite off Weatherbell Analytics.  Needless to say, the Gulf of Mexico is officially “open for business” and will help contribute to excessive rainfall totals and, as stated above, potentially a dangerous flooding event this weekend across central Indiana.

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Latest numbers averaged off a variety of computer models would place just under 4″ of rainfall down by noon Sunday, most of which falls between Friday and Sunday morning.  We note (2) waves of enhanced rainfall intensity set to impact the region.  As of now we’re targeting Saturday afternoon and again late Saturday night/ Sunday morning for extremely heavy rain, shown below.

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We still have time to watch the data and monitor the track of the storm.  It’s possible the “heaviest of the heavy” axis of rain shifts somewhat in the days ahead,  but it’s also important to note that even a light to moderate rain event combined with a frozen ground and a solid snow pack still in place will lead to flooding problems here across central Indiana.  The question of whether or not we’ll deal with flooding here this weekend shouldn’t be asked, but instead the question that remains is just how severe will the flooding be?  Stay tuned and if you live or work in a flood prone area, we would recommend preparing now for flooding.

Now, as we look ahead and focus on the Christmas to New Years period our thoughts will shift from a flood threat in the near term to one that’s more wintry.  We’ll turn dramatically colder Sunday afternoon behind the big rain storm and that will set the stage for a colder-than-average run up to Christmas. In fact, latest raw numbers off some forecast model guidance has some frigid readings ahead next week (upper single digits not ruled out for lows).

The upcoming 10 days off the European forecast model charts show an interesting scenario with the coming thaw, but the key word is brief.  Note days 6-10 are back into a colder-than-normal regime.

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Additionally, we think we’ll have to deal with another storm prior to the New Year period and with the colder air back in place, there’s the threat we could have to contend with a wintry side to the next storm.  The details with storm number two will have to wait until we finish dealing with the first storm and associated serious flood threat it’s presenting.

Permanent link to this article: https://indywx.com/2013/12/18/a-lot-of-weather-to-talk-about/

Dec 18

Significant Flood Situation Ahead…

Your latest 7-Day video forecast can be found in the video player to the right of this post.

We’ve known for over a week now that we’ll have to deal with a pre-Christmas storm. Latest guidance suggests our region undergoes a 3-4 day thaw with a decidedly warmer southwest flow ahead of this storm.  Additionally, with the more northern track of the surface low, we’re looking at nearly all of the precipitation associated with this storm falling as rain.  Combine our frozen ground with a significant early-season snow pack and multiple inches of rain ahead in the Thursday night through Sunday time period and the stage is set for a significant flood situation this weekend.

Here’s a look at what the latest forecast models show.  We’ve posted the GFS, Canadian, and European models below to display total rainfall between Thursday through Sunday.  The majority of this rain falls in two waves- Friday and again late Saturday into early Sunday.

gfs_total_precip_east_22cmc_precip_by10_east_1ecmwf_tprecip_indy_21

If the rainfall numbers are even half of what is projected above, we’re looking at a significant flood situation.  Needless to say, if your property is in a low-lying area, or one that is prone to flooding, I would begin to prepare now for major water rise in the days to come.

Much more later!

Permanent link to this article: https://indywx.com/2013/12/18/significant-flood-situation-ahead/

Dec 16

Major Storm Brewing This Weekend, But Details Are Murky…

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.

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Now, here’s a look at the latest European ensembles (left), again valid Saturday-Monday.

Geopotential32at32500hPa_North32America_120Geopotential32at32500hPa_North32America_144 Geopotential32at32500hPa_North32America_168

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/2013/12/16/major-storm-brewing-this-weekend-but-details-are-murky/

Dec 16

Have To Love “Over-Achieving” Clippers…

Good Morning, Hoosiers!  We’re awaking to a snowy commute, as promised, but our little clipper could certainly be called an “over-achiever.” We’re receiving many reports of snowfall amounts of 1.5″…

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Permanent link to this article: https://indywx.com/2013/12/16/have-to-love-over-achieving-clippers/

Dec 15

Tracking Two Light Snow Producers

Following on the heels of another early winter weather maker, we’re tracking renewed cold blowing into the region and two light snow producers the next couple of days.  The first clipper system will likely deliver some light snow accumulations (generally 1″, or less) tonight into the wee morning hours Monday.  The latest short-term, high-resolution, model data is picking up on this nicely.  While we’re not looking at significant snowfall, it’ll be just enough to lead to a slick Monday morning commute for some, especially from the city and northern ‘burbs.

Here’s a look at the simulated radar valid for this evening at 10 o’clock.  Light snow is spreading back into central Indiana.

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Additionally, we’ll keep an eye on yet another fast-moving clipper Monday night and early Tuesday that will also have the potential of dropping a quick light accumulating snow (again, most likely 1″ or less).  All-in-all, we’re still locking tightly into Old Man Winter’s grip the next few days.

Permanent link to this article: https://indywx.com/2013/12/15/tracking-two-light-snow-producers/

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