Category: AO

Trying to Answer Questions When Winter Will Show Up…

Daily, we’re receiving questions around if and when winter will show up. While admittedly later than originally thought here, we’ve never been in the camp of “throwing the towel” in on winter. Our winter outlook that includes below normal cold and near average snowfall remains unchanged.

Before we get into some of our reasons why we think winter will show up (and likely make up for lost time), the upcoming week will remain much warmer than average.

We’re tracking (3) storm systems that will deal the region rain over the upcoming week:

  1. Southern IN this afternoon and evening
  2. All of the state Monday
  3. All of the state next Friday into Saturday

As a whole, rainfall amounts won’t be particularly impressive for most, with 7-day totals between 0.25″ to 0.75″ for central portions of the state. Heavier amounts can be expected across southern areas.

Now, let’s look ahead to some potentially colder times. Before moving forward, it’s important that we recognize models have attempted once already to drive in a wholesale pattern change to colder (originally thought to be underway now). Perhaps it’s a case of “delayed, but not denied.” There’s a lot going on behind the scenes:

  • Sudden stratospheric warming event and potential polar vortex displacement, etc.
  • SOI flipping from a Niña-like state to one we’d expect to see associated with an El Niño
  • Active MJO remains

There are significant changes brewing in the arctic/ higher latitudes that have to raise an eyebrow at the very least.

Today

Mid-January

Note the higher pressures building over the upcoming 10-14 days in the arctic regions.

Not surprisingly, the models begin to tank the AO.

The PNA rises…

Something that also lends credence to a potential pattern shift is the recent SOI drop.

This would tend to suggest that an active storm track may be in place as the more bonafide cold shift is underway.

The moral of the story? Despite the milder period being extended a couple weeks longer than originally thought, there’s still a lot on the table this winter. It’s far too early to think winter’s over before it’s really even begun for most. We expect to see increasingly wintry conditions show up around the middle of January…

Stay tuned.

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Deeper Look Into The Long Range…

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“Pulling The Curtain Back” On The Late December Pattern…

Late December through early January is a critical time period where most folks (even those maybe not normally interested in the weather) are glued in on the forecast.  For some, they’re rooting for a white Christmas, while others are preparing for holiday travel to see loved ones.  The idea here of a transitional pattern remains and this should promote active weather during the holidays this year.

Understanding things can change with respect to timing from this distance (in some cases 2+ weeks out), these are the dates we’re targeting for storm impacts across central Indiana:

  • Dec. 20-21
  • Dec. 24-25
  • Dec. 27
  • Dec. 30-31

Before we talk specifics, it’s important to look at some of the pattern drivers.  Some of these drivers include teleconnections such as the NAO, AO, PNA, and MJO.

Forecast indices with respect to the AO, NAO, and PNA are expected to be more or less neutral through the late month period.  This is what the respective teleconnection “state” would result in the temperature department across the country.

Arctic Oscillation

North Atlantic Oscillation

Pacific North American Pattern

The basis of our late-December forecast is built from the MJO, or Madden-Julian Oscillation.  We note the MJO is expected to rumble through Phase 4 before heading into Phase 5 around Christmas.  Phase 4 (image 2 below) is a warm phase and correlates well to what the week ahead will provide.  However, Phase 5 (image 3 below) is a colder phase and could “up the ante” for the potential of wintry weather around Christmas.

If the MJO amplitude remains, it’ll roll into Phase 6 to close the month and open January.  Here’s how that would correlate in the temperature department:

The upcoming week will run milder than normal- lining up perfectly with MJO Phase 4.

The first of our targeted holiday storm systems will come at the tail end of the warm Phase 4 and will likely deliver a wind-whipped rain in here as early as Wednesday night and Thursday morning.  However, as the storm pulls northeast along the Ohio River, it’ll deepen on its journey into the eastern Great Lakes region.  This will help pull colder air into the region, likely resulting in rain transitioning to snow Friday.  Given the path of the storm, this doesn’t favor some sort of prolonged backlash snow event, but it could be enough to result in accumulating snow across eastern Ohio Valley sections and downwind of the snow belt regions of northern IN, OH, and MI.

The pattern, as a whole, appears to be one of transition to close the month and open January and it’s not really until we get to mid-January where we think all of the drivers “align” to create more of a lock and hold cold pattern.  With that said, a stormy late December pattern can present problems, even in the midst of relatively mild times.  We’ll be here to dissect the storms as they come throughout the holiday season…

Permanent link to this article: https://indywx.com/pulling-the-curtain-back-on-the-late-december-pattern/

Here Comes March: What We’re Saying (And What We Aren’t)…

2018 is already flying!  As we welcome in March here are the weather statistics for IND (Indianapolis).

  • Average highs start off in the middle 40s on the 1st and rise to the upper 50s on the 31st
  • Average lows are in the upper 20s to begin the month and increase to the upper 30s by month’s end
  • We average 3.56″ of precipitation, including just under 3″ of snow

Before we look forward to March, let’s review where we’ve been in February.  After a very cold start to the month, eastern ridging really flexed it’s muscle and resulted in spring-like conditions for the better part of the past couple weeks.  As we type this up late on the 28th, IND is running 5° warmer than average.  (It’s been a wet month, too, as we’re close to 2.5″ above normal in the precipitation department).

The early spring “fling” has lulled many into believing winter’s finished.  While the worst of the winter is certainly behind us, we continue to think a dose of “reality” awaits as we progress through the better part of the first half of March.  To be more specific, we feel the period March 6th through the 20th will offer up below average temperatures and an active pattern- capable of producing wintry threats.

We note the (2) main drivers this time of year (the AO and NAO) are running negative through mid-month, which favors cold.

Sure enough, modeling is going to the pattern that will produce below normal temperatures (doesn’t appear to be anything particularly frigid, but colder than average, nonetheless) through mid-month.

With blocking in place, an undercutting jet will serve to deliver an active storm track.

Keeping in mind March winter events need multiple items to come together to create impactful situations, it’s also important not to simply “buy in” to the idea that just because it’s been warm lately that winter is finished.  March can be a wild month, as long-time Hoosiers are aware.  The pattern we’re heading into over the next 10-14 days is one that’s been void most of the winter (high latitude blocking in place) and can serve as the player needed to flip a “nuisance” variety late-winter event to one that’s much more significant.  We’ll need to remain on guard for the potential of one or two “more significant” wintry events as we move through the first couple weeks of the month.

Finally, looking ahead, there’s an argument that can be made that we flip the script towards milder times through the last (10) days, or so, of March.  We note (as shown above) the AO and NAO trend neutral-to-positive mid and late March.  Secondly, the EPO is also expected to flip positive for the second half of the month and this is warm signal, locally, as shown.  Majority of guidance also takes the MJO into the “null” phase late month.

The end result is one that should promote colder than average times over the next couple weeks, overall, along with an active storm track.  With blocking in place, the potential of one or two more significant late-winter events are on the table, and we’ll have to fine tune specifics as the individual storms come.  While confidence is high that someone within the Ohio Valley region is likely to still deal with a big-hitter event, there’s no way to get specific until the individual players are on the field.  Thereafter, the pattern should begin to transition to one more conducive for “stick and hold” spring conditions during the latter portion of the month.

Permanent link to this article: https://indywx.com/here-comes-march-what-were-saying-and-what-we-arent/

Saturday Morning Rambles: Periods Of Heavy Rain Early Next Week…

I. A weak weather maker will help spread a mixture of light rain and snow across the state later today, particularly this afternoon and evening.  Precipitation amounts will remain light and insignificant, but serve as a nuisance as you go about your weekend plans.

II.  We’re hopeful for much needed sunshine Sunday as we’ll be in between storm systems, however any sun that we see won’t last long.

A rather ominous setup for heavy rain will take place Monday into Wednesday.  This will include a combination of ingredients as a strong southeast ridge will prevent much forward motion of a “wavy” front that will drape itself across the Ohio Valley region.  Additionally, the subtropical jet will transport moisture-rich air northward into the area (true Gulf of Mexico connection).

While this is an unseasonably warm pattern (we forecast highs of 50°, or above, 5 out of 7 of the upcoming days, and at least 2 60°+ days), it’s one that will likely result in periods of heavy rain not only next week, but in waves over the upcoming 10 days.

Widespread 10-day rainfall numbers of 3″ to 4″ will be likely in this setup, including locally heavier amounts of 5″ to 6″ in spots.  Certainly, if you live near waterways we suggest having a plan in place as it’s not a matter of if, but when flooding takes place in spots across the region with such a setup.

III. Longer-term, we still need to be wary of the potential of a colder pattern returning as we get into March.  That forecast deep negative arctic oscillation (AO) has to raise an eyebrow for the possibility of making up for lost time in the cold weather department before we can signal “all clear” on winter…

Permanent link to this article: https://indywx.com/saturday-morning-rambles-periods-of-heavy-rain-early-next-week/