• Category Archives Ensemble Discussion
  • 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…

  • Warm & Windy This Weekend; Changeable Weather Next Week…

    Central Indiana will enjoy a nice open to the weekend. High pressure will scoot off to the east and allow a warmer, but blustery return southwesterly flow. Though we’ll be warmer tomorrow, winds will increase and gust to 30-40 MPH late in the day. Highs will top out in the middle to upper 70s.

    Sunday will feature an increase in cloudiness, but most shower activity should remain across northern and north-central parts of the state. Even in areas that receive rain Sunday, amounts will be light and insignificant. Here’s a look at what the radar may look like Sunday afternoon. It’ll be another unseasonably warm day as highs top out between 75°-80°, despite the increase in cloud cover.

    Speaking of warmth, that will be the major story for early and middle parts of the work week. Highs around 80° and warm overnight lows in the 60s (where our average high should be) can be expected with dry, but windy, conditions in play. Extended summer, anyone?!

    Changes are brewing for the latter portion of the week and that will require most of our attention over the weekend as far as sifting through the various details. While confidence is high in a transition to drastically cooler conditions, the evolution of specifics concerning rain chances results in a much lower level of confidence. As it stands now, we’ll increase rain chances for the late week period (late Wednesday into Thursday), but the duration of wet weather is up in the air. The GEFS (below) shows the wetter pattern returning.

    Note the various ensemble solutions (above) of how the upper air pattern may look in the 8-10 day period. Solutions range from a drier and downright chilly look (European) to one that’s cooler, but still unsettled (GFS, GEM). Time is required to continue to fine tune things.

    All of that said, as previously mentioned, we’re much more confident in the cooler look to close October. The GEFS sees that, as well.

  • Mid Week Showers Followed By A Pop Of Cool Air…

    Mid and high level clouds are streaming overhead this evening and will help set up a brilliant sunset across central IN.

    screen-shot-2016-10-10-at-6-57-58-pmTuesday will remain rain-free across the region, along with pleasant temperatures and humidity levels (mid 70s after a low in the lower 50s).

    Moisture will continue to be transported northward Wednesday, courtesy of a gusty SW breeze at times.  As the approaching cold front interacts with the moisture return, scattered showers will “blossom” across the area Wednesday night into the wee morning hours Thursday.

    wednightshowersRainfall amounts don’t look particularly impressive; generally 0.10″-0.25″ during the Wednesday night-Thursday morning time frame.

    17The cool air flowing in behind the front is impressive though.  In fact, highs both Thursday and Friday will likely only reach the lower 60s (if that).

    12Despite the chilly air that will be with us to wrap up the work week, ensemble data is in excellent agreement on a significant warmer than average regime developing under a big eastern ridge in the 6-10 day.  This will likely promote highs into the lower 80s next week for a few days.  Impressive, no doubt, considering we’ll be rumbling through the second half of October by that point.