• Category Archives Ensemble Discussion
  • Bet On The Cold…

    During wholesale pattern transitions, operational data will struggle at times, including some wild run-to-run swings.  Earlier this week, the European wanted to put early next week in the lower 50s.  At the same time, the GFS suggested lower single digits.  Precisely, it was a difference of 46° between the two models for a high?!  🙂

    We note the teleconnections (in particular, the EPO) are aligning in a manner conducive for widespread cold.

    The GEFS might be a bit quick on dropping the arctic hammer, but the consistency of the model is impressive.  Meanwhile, the European (even it’s ensemble data) has been much less consistent and has really been struggling the past couple of winters, overall, as a whole.

    While we can argue as to just how cold it’ll get through the early part of February, the overwhelming message is that a prolonged colder than normal pattern will develop during this time period.

    Let’s also keep in mind that the initial cold onslaught is coming in the face of the MJO still rumbling through the warm phases.  We note the European is consistently having to correct towards a more “amped up” MJO- swinging into the cold phases as we approach mid-month.  And it’s mid-February that continues to have us concerned for the potential of truly nasty, severe cold.

    As for snow, it’ll come in this pattern.  Again, don’t get caught up in the operational output, but understand that the pattern over the upcoming 7-10 days favors numerous fast-moving snow systems.  While most of these will be light, we’ll have to keep a close eye on things as the potential exists for one of these waves to spin up a moderate event.

    As we look ahead to Week 2, the potential is there for a more widespread significant phased interior threat prior to the dumping of the bitterly cold air for mid-month.

    As it is, both the GEFS and EPS “mean” paint a bullish signal for piling snow up over the next couple weeks…

  • Arctic Hammer Drops Down Around Christmas…

    While the evolution of how things transpire from a snow perspective are “murky,” at best, confidence continues to run very high on the prospects of a nasty period of bitter air arriving around Christmas.

    Before we dig into the cold details, the pattern is one that still screams “trouble” from a wintry perspective in the December 23rd-Christmas Eve period.  We posted over the weekend of the PNA-EPO going to battle Christmas weekend, and before the cold overwhelms, a consensus of the data continues to paint an interesting scenario as resistance will be present initially from the southeastern ridge. Modeling will continue to struggle with this evolution over the next few days, but we’re hopeful we’ll begin to gain more clarity by late in the work week.  Needless to say, a stripe of impactful wintry precipitation should fall in a southwest-northeast fashion given the pattern, but whether that’s to our northwest, over our region, or off to our southeast is simply impossible to call from this distance.  A glance at the individual ensemble members (GEFS shown below) shows this nicely, as well.  The European ensemble members also paint a similar picture.

    Hang in there as we continue to sort through the data over the next few days.  Once confidence increases (for or against an event), you’ll be the first to know! 🙂

    Now to the ugly stuff:  Bitterly cold air of true arctic origin will be dislodged southeast late week and encompass more of the country by Christmas weekend.  Eventually, this arctic air will make it across the Appalachians and reach the East Coast just after Christmas.

    Recent operational data (GFS and Canadian included) has suggested a sprawling high in the range of 1050mb+ descending into the eastern slopes of the northern Rockies.  Such a regime would be plenty capable of spreading sub-zero temperatures east into the Ohio Valley (with or without snow on the ground).  Add in a biting north wind and wind chill values would drop to levels of dangerous and deadly levels if any length of time was spent outdoors.  Some of the latest data paints a picture similar to shades of the famous ’13-14 winter (20° to 30° below zero chill factor).  If you have travel plans over the Christmas holiday, please plan in advance to have a winter survival kit packed and loaded.  It absolutely never hurts to be prepared.

  • Tuesday Evening Rambles: Wintry Weather And More Christmas Week Chatter…

    I.) The pattern we’re currently dealing with is one that presents multiple challenges in the near term.  East-central and northeastern portions of the state have gotten in on the snow act today, but, so far, most of central Indiana has missed out on the snowy goods. With such a fast-paced northwest flow, we have to remain on guard for potential “surprises” in this pattern.  Perhaps the HRRR is beginning to pick up on this.  Latest runs want to deliver a “pop” of snow Wednesday morning, associated with “warm” air advection (WAA).  We’ll monitor tonight.

    9a forecast radar Wednesday

    II.  The northwest flow will continue to provide disturbances plenty capable of producing periods of snow again Wednesday evening through the end of the week.  Are these monster storms?  Hardly, but they can “suddenly” become sufficient enough to create travel problems given the pattern.  For those who live across the northern half of the state, plan to keep close tabs to local forecasts if you have travel plans through the end of the week.

    III.  A period of brief moderation will come in this pattern early Christmas week, but all eyes continue to focus on the period between December 22nd through December 26th for the potential of impactful weather across our region.  For model “worshipers” out there, we suggest paying more attention to overall trends, and a blend of ensemble data, as opposed to specifics associated with operational runs.  It’s a “jailbreak” pattern of sorts as true arctic air will be pouring down the Plains while the southeastern ridge tries to fight for a time.  The resistance from the southeastern ridge and associated tight thermal gradient should promote a very stormy regime for the interior (Ohio Valley into the interior northeast) as we head into the true holiday/ Christmas stretch.  As of now, we favor the idea of multiple waves along the pressing arctic boundary, as opposed to one big storm.  Looking back through the records shows some of the heaviest snows at IND have come from similar set-ups.  Understanding each set-up is unique, the overall pattern does have to raise an eye brow for potential of wintry weather in, or around, our region as Christmas approaches…

  • Intriguing Look As We Move Closer To Christmas…

    Temperatures will attempt to approach seasonal norms Monday (average high this time of year is 40°) before arctic reinforcements blow into town Monday night and Tuesday.

    This will keep highs in the middle 20s Tuesday with wind chill values in the single digits and teens most of the day.

    Scattered snow showers and embedded lake-generated squalls will accompany this arctic surge Tuesday.  As the wind trajectory sets up shop Tuesday afternoon, lake effect snow bands will impact portions of northeast and east-central Indiana.

    4a forecast radar Tuesday
    10a forecast radar Tuesday
    5p forecast radar Tuesday

    Cold weather will continue to dominate through the work week and an additional upper level disturbance may try to ignite snow showers Thursday.

    As we push into the 8-10 day time frame, a “relaxation” of the cold is anticipated, but, as we’ve been discussing, any sort of moderation will be brief in this weather pattern.  Cold looks to continue to dominate, overall.  With that said, there will be a window of opportunity early next week where temperatures will go above normal for a change and the European ensemble shows this brief moderation nicely.

    This doesn’t last long as the pattern begins to reload as Christmas week approaches.  As the evolution to a fresh cold pattern takes place, there’s a window of opportunity present for a more significant wintry system to potentially impact the Ohio Valley into the Mid Atlantic region.  Notice the relatively “flat” ridge across the southern tier and associated tight thermal gradient.  This look suggests we need to be on guard for the chance of a storm system to ride the thermal gradient in a west-to-east fashion, and has wintry implications for our region.  Far too early for specifics; just know the possibility looms of a wintry event, locally, as Christmas week nears.

    Speaking of Christmas, it sure appears as if cold will overwhelm the pattern for Christmas, itself, and the overall cold regime doesn’t show signs of letting up (with the exception of potentially a day or two) into the new year.

  • Colder Pattern Ahead To Close October; Open November?

    October, month-to-date, has been nothing short of a blow torch.  Officially, IND is running +9° through the 11th.

    In coffee shops and my travels around the great state of Indiana, I’ve overheard lots of talk centered on because October has been so warm, another lackluster snow season awaits.  Let us remind you that the infamous snow season of ’13-’14 featured a very warm first half of October.

    The upcoming 7-10 days will feature more of a transitional period of weather that we’ve come to know and love around these parts.  Warmth will spread northeast this weekend ahead of an approaching cold front (around 80° Saturday) before falling temperatures Sunday afternoon behind the frontal passage.  The chilliest air so far this season will descend upon the region early next week. That said, the chill won’t hold and another surge of above normal warmth will spread northeast by the latter parts of next week.

    A more significant pattern change appears dialed up prior to Halloween and this is one that seems suited to lead to more prolonged and significant cold to wrap up the month and head on into November.  Notice the evolution of things from October 21st to the 25th, courtesy of the GEFS off the fantastic tropicaltidbits.com.  Other model data is in general agreement, leading to a rather high confidence level for this time period.

    It should also be noted that analog data and research also would lean heavily in the cold direction to wrap up October and these findings also favor a chilly November… More on that later!  Speaking of later, an updated 7-day will be posted this evening.  Make it a great day!

  • Winter Returns…

    January got off to a frigid start.  Remember this coast-to-coast cold, including sub-zero temperatures across central IN, during the first week of the month?

    t0-1024x818After the past week to ten days, that frigid open to the month seems like forever ago!  The past 7-10 days has featured a significant January thaw, and temperatures now, MTD, are warmer than average across the Ohio Valley.  Warmest anomalies can be found across the southeast region.

    conus_mtd_t2max_anom_2017That said, the pattern is shifting back to winter for the last week of the month and while the duration, longer-term, can be argued, the next 2-3 weeks appear to offer an opportunity to play “catch up” in both the snow and cold departments.  Note the developing eastern troughiness.  This will bring colder air back into the east as we close January and open February.  The GFS ensembles, courtesy of Tropicaltidbits.com, also develops an interesting “blocky” look towards the end of the period in Week 2.  Should this verify, it would lead to a better chance of the cold, active pattern locking in.

    You’re corresponding temperature anomalies show the shift back to a colder than normal regime.

    Days 2-6
    Days 2-6
    Days 4-8
    Days 4-8
    Days 6-10
    Days 6-10
    Days 12-16
    Days 12-16

    A fast northwest flow will also result in multiple “pieces” of energy rotating southeast and we’ll forecast a period of snow showers by mid and late week, continuing into the weekend.  There’s the chance of a stronger clipper system sometime in the Sunday-Tuesday time frame that we’ll have to keep a close eye on.  We want to stress that global modeling will struggle with the specifics (timing and strength) of these clipper systems until within a couple days.

    Longer term, while confidence is high on the evolution to a cold, wintry regime through the medium range, the longevity and sustainability of the cold is in question.  For instance, by Day 10 (as the GFS continues to drill cold into the region), the European ensembles are much less impressed and suggest the overall transient pattern we’ve dealt with for the balance of the winter continues:


    ecmwf-ens_T850a_namer_11Thinking here at IndyWx.com believes the European is likely rushing the warmer central look.  Time will tell…

    **We do note the NEW European Weeklies lock a period of cold into the east from mid-February through early March, including a stormy (snowy) look.  Will Old Man Winter have the final say?

    Updated 7-day later this evening!

  • A Word (Or Two) On Where We Think This Pattern Is Going…

    Before we get into the updated thinking on the pattern, lets review what we have out:

    • Step-down process to cooler/ colder weather begins in mid-November.
    • Thanksgiving-Christmas period, as a whole, turns wintry and is snowier than average.
    • Our complete 2016-2017 Winter Outlook can be found here.

    The first week of November has featured an incredibly warm start to the month. (Image courtesy of MRCC).

    month-tdevSpeaking of warmth, 2016 has been a very warm year.

    ncep_cfsr_t2m_anom_ytd(The cold of 2014 seems so long ago…)

    ncep_cfsr_t2m_anom_2014Back to present.  We’ve targeted the middle part of November to finally beginning “bucking” the recent warm trend.  This won’t happen overnight and will be a battle of back and forth, initially.  Thus, the “step-down” label.  To be clear, November, as a whole, will finish much warmer than average.  It’s virtually impossible to counter the incredibly warm start.  That said, we do anticipate “jabs” of colder air working in here over the next couple weeks. For instance, this weekend will feature lows in the 20s for most and highs not making it out of the 40s Saturday afternoon.  (The average low and high at IND Saturday are 37 and 54).

    Despite being in a weak La Nina, the pattern is taking a while to respond.  Remember, we’re coming off one of the strongest El Ninos on record.  Until we slow the PAC jet, significant, long-lasting, changes won’t occur.  We can lean on the AAM (Atmospheric Angular Momentum) forecast for clues as to when this may occur.  You can read more about the AAM here.  My fellow local weather compadres, Michael Clark, Ed Valley, and Kirk Hinz have also written/ blogged extensively about the AAM and resulting impacts.


    gfs1When we look at the AAM forecast (above), we note the westerlies may begin to slow (indicative of the negative values) in the 8-10 day period.  This is crucial and, simply put, has to happen for the pattern to begin shifting into more of a position to allow sustained cold to enter the equation.  We want to reiterate that this, in and of itself, doesn’t create the cold, but instead allows the pattern to begin shifting away from the Nino-like (warm) regime into more of a La Nina pattern, as a whole.  – Hey, you have to start somewhere.

    If we can finally get the westerlies to slow, other elements are in play that could (and should) lead to a colder pattern as we move forward.  Our (3) big teleconnections are in a position favorable for cold for mid/ late November, into early Dec.

    cw5yrrsxaaefhiy-jpg-largeAdditionally, the EPO is forecast negative off the GEFS and EPS. (Images courtesy of Weatherbell.com).


    gefs_epo_12Again, this is a cold signal. (Image courtesy of Madusweather.com).

    eponew_neg_11novThe ensemble data is also beginning to key-in on higher heights (blocking) developing over the top.  Notice the significant changes in the overall look to the pattern between now and days 11-16. (Images courtesy of Weatherbell.com).

    cw5qrw0wgaaphxr-jpg-largeIn summary, and in the face of *most* seasonal data that is screaming warm, warm, warm, we still don’t have any significant changes to our overall thinking of “step-down” mid-November giving way to more sustained wintry-like conditions in the overall sense from the Thanksgiving-Christmas period.  Time will tell and only the Good Lord knows what the future holds, but we’ve done far too much work and research to throw the “game plan” in the trash before the game even begins…