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  • Shift Back To A Cold Pattern Awaits; What About Winter Storm Potential?

    December-to-date is running colder than normal (to the tune of 2.2 degrees at IND), but the past (7) days has seen a flip in the frigid 1st half of the month.

    December temperature anomalies, courtesy of Weatherbell.com.
    December temperature anomalies, courtesy of Weatherbell.com.
    Temperature anomalies the last 7 days. Courtesy of Weatherbell.com.
    Temperature anomalies the last 7 days. Courtesy of Weatherbell.com.

    The “relaxation” is temporary.  Modeling continues to advertise the recent “thaw” will give way to increasingly bitter times as we get deeper into the New Year.  By New Year’s Day we note the positive heights continuing to establish themselves across Alaska and Greenland (cold and stormy signal).  We also note the southeast ridge present, though to a lesser degree than over the past week.

    jan1By Day (10), the cold pattern is well established over the Lower 48.  This is a coast-to-coast cold signal (heart of the cold centered over the west and central) depicted by the European ensemble, along with other modeling.


    ecmwf-ens_t850amean_namer_6Teleconnections support a cold pattern returning.



    pnaThe agreement amongst teleconnections is nice to see and ups confidence in the overall direction of where this pattern is heading in regards to colder than average times looming.  The negative PNA correlates nicely with the SE ridge that continues to make itself heard from time to time over the next few weeks.  It should also be noted that the phases of the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO) become more of a factor for mid and late winter.

    As far as storminess goes, we’ll have to handle those as they come.  The overall pattern screams towards the idea of an active Ohio Valley to interior Northeast storm track as we move forward (continuing deeper into mid and late winter, as well).  That doesn’t mean one or two storms won’t bypass our local region to the south, due to strong, cold high pressure north, but the mean storm track should put areas through the Ohio Valley in the “sweet spot” from a snow perspective throughout the majority of January, and the rest of winter, for that matter.  Depending on the position and strength of the Greenland Block will have a lot to say about things.  Needless to say, storms cutting NW into the central Lakes should be few and far between after the New Year.  Speaking of storms, we have to continue to keep an eye on the second half of next week.  At the time of this discussion, the threat is still beyond the 7-day period, but circle late next week and weekend for the potential of wintry “mischief.”

  • 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…

  • Overwhelming Evidence On Mid Month Cold…

    The step-down cold pattern early January is ongoing, but we’ve been clear with our thinking of even colder air invading around mid month (Jan 10th-20th time period). We wanted to show the data that continues to come in supporting this idea.

    All three major teleconnections (AO, NAO, PNA) are aligning in a fashion that supports cold weather for our particular part of the country.

    The MJO suggests mid month cold rolls right through the next several weeks, as noted here.

    Ensemble data continues to support the cold idea.

    While individual storm systems with wintry potential will have to be dealt with as they come, it’s very easy and clear to see the shift towards a downright wintry feel in the days and weeks ahead…

  • A Word About What Lies Ahead…

    No need for model data or fancy graphs with this post, but instead we just wanted to level set with you on where we think we’re heading as we rumble into 2016 and deeper into winter.

    In short, we have zero change in our thinking since fall that though this winter would open warmer than normal in December, we would, in fact, have a winter to contend with (back loaded). Our reasoning behind this thinking has been laid out time and time again in our winter outlook and archived posts so there’s no reason to bore you again with those thoughts. 

    We think early January shifts colder from where we’ve been, but we’ve been saying it’s not until mid month where things can really lock in and crank. Though colder, the first half of January is likely to still be a bit transient. (By the way, there’s potentially a significant storm system waiting on deck week 2 that may be plenty capable of producing wintry mischief). That storm is the one that should precede the whole sale pattern shift to more sustained cold and snow across the Ohio Valley and Mid West region that carries us through the back half of the 2015-2016 winter.


    Week 2 shows an active southern stream and developing negative AO. Source: Tropicaltidbits.com

    To sum things up, we have absolutely zero changes to our ideas on the winter from back when we initially released our winter outlook. Winter is coming this year, despite what you may be hearing :-). 

    The transient 1st half of January will likely turn progressively colder in more sustained fashion for the 2nd half of the month. In the meantime, if you’re someone who likes to review each and every model suite as they come, have the dramamine handy, as wild swings will continue with operational model runs. Instead, we suggest leaning more towards the ensemble data as we work through this pattern transition (always tough on model data). 

    Much more later! As always, you can follow us on Twitter @indywx! 


  • Where We Stand…

    Some are beginning to grow tired of the seemingly unending warmth and lack of snow, particularly with an above normal stretch of weather coming that includes the Christmas holiday (though not nearly as warm as the European suggested as soon as only a few days ago).

    Month-to-date, December has been a warmer than normal month for most of the country. Source: Weatherbell.com
    Month-to-date, December has been a warmer than normal month for most of the country. Source: Weatherbell.com

    Our winter outlook stated we thought we’d get off to a warmer than normal start, but we were also very clear in stating we thought a rather marked shift to more sustained wintry conditions loomed for mid and late winter.  That period is drawing closer by the day and it’s time to “put up or shut up.”  By “mid winter” we mean mid January.  Yes, that means three weeks out.  Without holding back any punches, we’re fully expecting a colder than average period developing by then (and with staying power), along with plenty of opportunities for wintry precipitation.

    You can read our full winter outlook (published in October) here.

    The reasoning for our thinking has been outlined in previous posts and in our winter outlook, but, in short, it’s built on the idea of a weakening El Nino and a mean winter upper air pattern that includes W NA ridging (positive PNA regime).  Later in the season, a more sustained negative AO and NAO should establish itself that could carry the wintry regime into meteorological spring.

    Current Sea Surface Temperature Anomalies
    Current Sea Surface Temperature Anomalies

    We think we begin to progress into a “step down” process to the pattern explained above through the early stages of January, and the ensemble data is beginning to support this.

    GFS ensembles for early January. Source: Tropicaltidbits.com
    GFS ensembles for early January. Source: Tropicaltidbits.com

    The modeled W NA ridging is a far cry from what we’ve been dealing with over the past month.

    Now we caution that the initial step down to a more sustained wintry pattern won’t occur overnight.  We label it “step down” for a reason.  All the while, it’s a start in shifting away from the anomalous warmth we’ve been dealing with through the month of December.  Initially, cold air will only be marginal, but as things align into the mid/ late winter pattern and we expand snow cover, arctic air will grow in a more widespread fashion.  Something else we’ll begin to have to keep a close eye on?  A potentially active NW flow that features several clippers plenty capable of producing accumulating snow.  We note central-based Ninos are notorious for the clipper parade during the mid and late winter stretch.

    In the shorter term, a rather unsettled Christmas week looms.  Modeling will continue to “sure up” the handling of a rather complex storm system after Christmas, as well.  We note runs that have pumped out copious rain numbers and others that suggest wintry precipitation may fall as the cold upper low ejects northeast.  We’ll continue to monitor.

    In the meantime, gear up for a rather wet Monday.  We think one half inch is a good bet across the area, with locally heavier totals.  Our updated 7-day in the morning will be a rather busy one.  Talk with you in the AM!


  • Iron Bowl Saturday: December Rambles…

    This is a special day in the McMillan house.  Iron Bowl Saturday only comes around one day a year… Needless to say, the Auburn flags have been on the vehicles since Wednesday, we’re decked out in our orange and blue, and game faces are on for this evening’s matchup.  WAR EAGLE!

    As we get set to flip the calendar to December, we wanted to post some latest thinking.

    Let’s take a look at the latest teleconnections.  As we’ve been talking, there’s a lot of “noise” in model land, including conflicting signals.  The positive NAO and AO argue for warmer than average conditions, while the positive PNA suggests chillier than normal times should prevail.

    We wanted to post the latest model predictions of each teleconnections, courtesy of Weatherbell.com.  Additionally, courtesy of madusweather.com, here’s what each teleconnection “phase” would normally lead to in December.


    Screen Shot 2015-11-28 at 10.55.21 AMNAOpos_12dec


    Screen Shot 2015-11-28 at 10.55.07 AMAOpos_12dec


    Screen Shot 2015-11-28 at 10.55.34 AMPNApos_12decSimply based on the teleconnections, you would build a December forecast that would lean more warm than cold, as the short term positive AO and NAO should trump the positive PNA.  As we look at the month, as a whole, the AO and NAO are forecast to trend more neutral, while the PNA remains solidly positive.  Does this suggest colder air, relative to normal, would invade mid and late month?  – Certainly something to watch.

    Additionally, the latest Southern Oscillation Index (SOI), has begun to take a negative hit.  This is after weeks of positive SOI values- relative to the base state.

    Screen Shot 2015-11-28 at 10.47.52 AM





    While it takes a while to impact the pattern, locally, this negative hit does suggest mid and late month could be a bit more interesting from a wintry perspective.  We shall see.

    The CFSv2 remains very consistent on a warm month, relative to normal, particularly across the northern tier.

















    While we can’t post the European weeklies here, the latest run suggests colder, and stormy times around Christmas week.  Now, we should also note the overall performance of the Weeklies hasn’t been as accurate compared to normal over the past few months, but it’s another interesting trend to keep an eye on.

    The MJO will begin the month in Phase 3 before going into the “wheel house.”  All-in-all, we don’t get a “hat tip” from the expected monthly MJO forecast, with the exception of Phase 3 to begin (warm phase).


    Screen Shot 2015-11-28 at 11.53.45 AMTo sum up:  Long range forecasting is always a gamble.  Only the good Lord knows what the future holds.  That said, there are times when we feel more confident about our long range, monthly outlooks, more so than normal.

    We’ll lean warmer than normal for December (+ 1.5 at IND), and this really plays into our Winter Outlook (slow start expected with the emphasis on the cold and snow mid and late winter), but that doesn’t mean we’re expecting a “boring” month.  Keep in mind November has been both warmer AND snowier than normal, with a very busy 2nd half of the month.

    We’ll have plenty of challenges to handle as we rumble through the month no doubt, but we expect the positive AO and NAO to trump the positive PNA to start to the month.  As we progress into mid and late month, we’ll have to be on alert for potential impacts of that significant SOI hit to open the month.  We’ll also keep the Weeklies in check to see if the colder, stormy look Christmas week remains.  It’ll be fun, as always.

    To close, here’s one more emphatic WAR EAGLE from our home to yours! 🙂