• Category Archives Jet Stream Discussion
  • 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…

  • July Outlook

    With only a few days left of June, thoughts are turning to the 4th of July holiday, getting those summer vacations taken care of before school starts back, and pre season football practice starting up.

    June will finish as one of the wettest on record, and coming on the heels of a very dry May, we’re actually right where we should be from a year-to-date precipitation perspective.

    Here are some highlights we’re focusing in on that’ll impact our July weather:

    • Highly amplified MJO
    • Very wet June through the Mid West/ Ohio Valley
    • Warm water off the East Coast
    • Persistent western ridging

    June will finish as a top 5-10 wettest June on record for many communities throughout our immediate region. With the wet conditions, it’s very tough to get any sort of long-lasting truly hot weather and while we’re certain to have plenty of warm, humid days during the upcoming four weeks (it is July, after all), we don’t anticipate any sort of significant heat wave. We fully expect being able to save on cooling costs when compared to normal.  We also note a highly amplified MJO, or Madden-Julian oscillation.

    In July, phases 6-7 are cool signals for our region.

     We note sea surface temperatures are quite warm off the eastern seaboard and in the Gulf of Mexico. While this doesn’t have a direct impact on our weather here in regards to temperature, it can suggest some southeast and eastern ridging at times. When we look at the upper air pattern below, we note the region will likely be in between predominant ridge positions east and west for July. The end result for our particular part of the country would be a cooler and continued unsettled time of things for the better part of July.

    *As a side note, this sort of water profile does “raise an eyebrow” for potential tropical activity in the Gulf and potentially along the east coast, and that’s something that we’ll have to keep a close eye on as we progress into the heart of the season.

    We sort through a variety of data to help build our weekly (client based) and monthly upper air charts. While we can’t share all of those forecast models here directly with you (due to licensing), a combination of GFS ensemble data, CFSv2, and European weeklies have helped us build this upper air pattern for July.

    July2015UAThis would provide continued cooler than normal times (particularly daytime highs, considering the wet ground) and a busy time tracking cold fronts and individual disturbances that will ignite frequent showers and thunderstorms.

    “Average” July weather for IND includes mid 80s for highs, mid 60s for lows, and 4.5″ of rainfall.  In summary, we anticipate July 2015 to run 2-3 degrees below average and precipitation to run above normal by a couple inches.  We think we just keep on rolling down the tracks from the wet and active regime put into place in June.  Time will tell!

  • Tuesday Evening: Cold Pattern…

    Quick couple updates this evening:

    Virtually all of today’s model data has jumped on a stronger storm system for the weekend as opposed to a flatter wave.  This leads to a more northwest track and would imply more “wet than white” for local precipitation types for the weekend.  One important difference between this upcoming event and those of recent past is that arctic air is now on the playing field and this can create all sorts of “havoc” in mid range modeling.  We’ll keep a close eye on things.

    The other HUGE item of business we want to get across is the prolonged and rather impressive cold pattern.  A series of arctic highs will come down the Plains and spread southeast the upcoming 7-10 days.  Despite a potential brief spike in temperatures Saturday, it’s a MUCH colder than normal pattern.  Eventually, we’ll have to closely monitor the potential of a couple of snow-producing clipper systems.  Sometimes these can be overachievers, depending on track and intensity and one of two clippers next week may be just that…

    More later!  Have a great evening!

    Jet Stream Forecast: New Year's Day 2015
    Jet Stream Forecast: New Year’s Day 2015


  • Talking Heat, Humidity, And Rain…

    Happy Saturday afternoon to all!  This evening’s video covers what continues to look like an active weather pattern, including multiple rain chances ahead for the upcoming week.  We also discuss the upper air pattern and the expanding area of heat.


  • Historic Snow Season Keeps Rolling Along…

    The winter of 2013-2014 is off to a rip-roaring start and, as we’ve discussed in previous posts, the mid to long range data suggests we remain locked in an exceptionally cold and snowy pattern.  Officially, as of this evening, the Indianapolis National Weather Service has posted some impressive stats (the full report can be found here), including:

    • Through Jan. 21st, the 24.4″ of snow ranks as the 3rd snowiest January on record.
    • Through Jan. 21st, the season-to-date snowfall of 33.2″ ranks as the 2nd highest on record in the period Dec. 1st through Jan. 21st.
    • Through Jan. 21st, the season-to-date snowfall of 33.2″ ranks as the 8th snowiest on record for an entire winter season.

    As we look ahead to the upcoming 7-10 day period, we note a continuation of arctic reinforcements- each which will be plenty capable of adding to the snowfall total.  Additionally, our cold air mass will only grow even more severe and bitter over time, including multiple days during the aforementioned period where central Indiana will go below zero.  Finally, there have been many questions concerning a potential big storm centered on early February.  I’m not sure where this rumor started, but it’s far too early to say with any sort of confidence any specifics around a possible big winter storm early February.  That said, as we’ll get into briefly below, the pattern does appear to be aligning itself in a way where a widespread winter storm is possible somewhere across the eastern half of the country.

    Okay, okay, back to the near term…  Let’s start with tomorrow!  After a cold and dry start to the day, our next arctic front will blow into the region during the evening.  Arctic fronts are notorious for having bursts of heavy snow rates in a scattered fashion and this appears to be the case as the next arctic front moves through Wednesday evening.  We bracket the hours of 5p-8p for the possibility of heavy snow bursts racing through central Indiana.  While these won’t last long, they’ll likely be intense- capable of depositing a quick 1″-2″ of new snow on a gusty northwest wind within 30-60 minutes.  White-out conditions and extremely heavy snowfall rates will accompany the heavier bursts of snow.  Latest high-resolution model data shows the heavy snow bursts accompanying the arctic front tomorrow evening:


    Thursday will be mostly dry and frigid, but all eyes will then begin to turn to our next significant winter event Friday into Saturday.  The pressure gradient between high pressure across the Mississippi River Valley and the next approaching arctic front (and associated low pressure) will really being to kick up the wind across our region Friday.  We’re afraid we deal with another round of severe blowing and drifting snow Friday, especially Friday afternoon and night.  Areas most suspect to drifting and blowing snow will be central Indiana’s open country and may not be too different from the problems our region dealt with Sunday into Monday morning from blowing and drifting.

    As we approach Friday night into Saturday, snow will overspread the region and will likely accumulate to the tune of a “few inches” during this time period.  Strong winds will remain, shifting from the west to the northwest and eventually north.  Open country will remain the prime place for continued severe blowing and drifting problems.


    Just as soon as Saturday’s snow systems exits stage right, we turn our attention to potentially another significant snow maker for the second half of the weekend.  Latest model data remains consistent on moving another potent clipper system into our region Sunday, including the GFS and Canadian forecast models.  We still have time to fine tune the precise track of the storm, but just north of the low’s track an additional 3-5″ type snow is possible Sunday.  Note the GFS and Euro in relative agreement on the track of the low, with the Canadian currently a touch further north. We’ll fine tune in the days ahead…  Experience with similar patterns from the past suggests central Indiana should brace for more accumulating snow Sunday.


    As for the brutal cold, we note multiple pushes of fresh arctic air behind each snow maker.  We currently target Thursday morning, Friday morning, Tuesday morning, next Wednesday morning, and next Friday morning as having the most likely shot at dipping below zero. The “coldest of the cold” likely means Tuesday morning takes the crown, with lows potentially dipping into the double-digit below zero range for central Indiana.  The European forecast model (below) even shows sub-zero temperatures making it as far south as the southern Appalachians.

    As we look even longer term, there have been many questions centered on the potential of a big winter storm for early February.  Before we go any further, we want to stress it’s far too early to make any claim of certainty to the above.  That said, there are items we can pick up on to a least “raise an eyebrow” that something of significance may be brewing… Do we mean for anyone to take that verbatim and to the bank?  Absolutely not.

    The European Weeklies suggest we need to keep an eye on the first week of February.  They show a potential phasing of the jet (where the northern and southern streams of the jet stream phase together- often times resulting in a big storm)… That said, we want to again stress this is far too early to be discussing with any sort of certainty.  Heh, the next week will keep us busy enough!

    Keep the shovel handy!  Snow removal companies, thank you for your service and hard work…hopefully you have plenty of coffee on hand!

  • 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.


    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!

  • Rambling Around Between Games…

    As we alluded to in the post earlier this morning, the weather pattern is beginning to get more active. As “seasoned” Hoosiers know, this is only the beginning of a rather “vamped up” weather period through the next 7-8 months around these parts. Yes, the lazy, hazy days of summer in the weather office are over.  Speaking of the weather office, I’m continuing to get settled into the new “home base” office. As I get settled, more and more products will begin to hit the site to help keep central Indiana Hoosiers abreast of what lies ahead in the weather department.

    As we look at the upcoming week, we’ll note the trough and dominant northwesterly flow of the weekend begins to “relax” by mid week and weak ridging takes it’s place. This will lead to a warmer and more muggy (though nothing close to as oppressive as last week) feel to the air by mid week. We also note another dip in the jet by next weekend. While details still have to be ironed out, there’s a good shot of rain due in here by week’s end along with another cool down by next weekend. I also want to point out the re-curving typhoon out in the western Pacific.  This is in association with upper level ridge placement in the Pacific Ocean and we can actually use this tool to help us forecast weather here on the “home front” in the 6-10 day period. That would bring us roughly to 09.25.13 (give or take a couple of days) and would line up nicely with the cool end of the month we’ve been talking about for some time.  Recall that we’ve said we anticipate a warmer than normal month to continue (in the overall pattern sense) up until the last 5-7 days of the month. Does this help set the stage for a colder than average October ahead? Stay tuned…

    Here’s a look at our precipitation outlook, compiled this afternoon using a variety of short and mid range forecast models.


    Watch how the troughs (cooler air) and ridging (warmer air) correlate with the temperature pattern in our official forecast (posted earlier this morning).









  • Wednesday Jet Stream Discussion

    We use the Jet stream as one of many tools to help us forecast the weather in the days to come. A new feature here at IndyWx.com will be a Jet Stream Discussion, updated a few times every week to help you, the viewer, get a better idea of what to expect in the week ahead!








    Note that the upcoming (7) day period will feature many “ups and downs” in the jet stream pattern.  This is indicative of the changing of the seasons and very typical of the approaching fall season.  Unseasonably cool air will be associated with the dip (known as a trough in the meteorological world) in the jet stream Thursday through Saturday. Temperatures will fall through the day tomorrow, after morning highs in the middle to upper 70s, and Friday and Saturday will feature air temperatures well below normal (by some 10 degrees).  That said, the cool weather is “transient” and will be out of here almost as quick as it arrives.  We’ll warm back to seasonable and above average levels during the early to middle part of next week as ridging builds into the Mid West and Ohio Valley region.  In fact, temperatures well into the 80s to near 90 degrees can be expected by the middle/ latter part of next week.

    As for precipitation, we anticipate a broken line of showers and embedded thunder to push into the region with the cold front later tonight and Thursday (not a big deal and most won’t get wet). On average, those that do see rain will only muster a couple tenths of an inch.  The next best chance of precipitation isn’t until late next week.

    We hope you enjoy these hand drawn maps.  The way weather information is provided to you, the viewer, seems to become more and more digital with less of the “human influence.” Our goal, as always, here at IndyWx.com is to keep the human element in the forecast products you see here.

    Our full forecast package will be updated later tonight.  Have a nice and relaxing Wednesday evening and be sure to follow us on Twitter- @indywx or like us on Facebook (IndyWx.com).