Is a weekend winter storm brewing?
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Category: GFS
Permanent link to this article: https://indywx.com/2019/02/27/all-access-video-model-differences-on-potential-weekend-winter-storm/
Feb 20
It Was A Case Of Delayed, But Not Denied…
While arriving later than originally expected (recall we originally thought the cold, wintry pattern would start on the 18th), it sure appears as if this was a case of “delayed, but not denied.”
The latest GFS and European ensembles are keying in on a significant pattern change as we put a wrap on February and open March. (Looks like we were about a week early in jumping on the cold bandwagon).
First and foremost, there’s excellent overall agreement amongst data (increases confidence significantly during the medium to long range period).
Days 1-5: Southeast ridge continues to dominate during the short-term period and there’s no high-latitude blocking to speak of. This suggests storms will continue to “cut” northwest of the region and place central Indiana in the “warm” sector, with transient, backlash cold/ snow potential.
Days 6-10: Significant changes begin to take place as heights (ridging) builds across AK. This is important as it can help “dislodge” late season cold air (and send it southeast). The SE ridge is also in the process of getting squashed during this period. We’ll likely transition away from the moisture-laden storm systems and replace with faster, overall weaker, systems that will be more capable of producing wintry precipitation.
Days 12-16: A total transformation of the pattern has taken shape since the Day 1-5 period. The new ‘mean’ trough position takes up shop across the East with the AK ridge continuing to dislocate late season arctic air southeast. The GEFS also shows a reflection of a southwest ridge which can be helpful in the overall storm track that could potentially deliver more “meaningful” wintry systems across the OH and TN Valleys as we get into the first couple weeks of meteorological spring.
Side notes: We’ve reviewed the crashing SOI index and this increases our confidence in a much colder pattern developing (typically takes place around 10-12 days after the crash begins). We’ve noted the deeply negative values against the base state which would suggest the cold pattern should continue for some time. We still believe the pattern remains colder than average, overall, through the 1st half of March.
The latest deeply negative EPO adds fuel to the fire in the idea of a cold open to March.
Given this, there should be no surprise to see the cold anomalies showing up on the latest medium-long range ensemble guidance:
It sure appears March will come in like a lion; will it go out like a lamb?
Permanent link to this article: https://indywx.com/2019/02/20/it-was-a-case-of-delayed-but-not-denied/
Jan 07
Weekend Threat: Subtle Differences Make All The Difference…
We wanted to take a quick opportunity to discuss the weekend snow threat. While certainly on the table, it’s far from etched in stone. We note the models doing their usual “herky-jerky” moves 5-6 days out. At the end of the day, there’s a notable threat present, but we prefer to watch things unfold over the next few days before beginning to get too excited.
Subtle differences between the European model (image 1) and GFS (image 2) are seen in the handling of the 500mb pattern. The GFS is quicker to phase the upper energy and leads to a more robust system. The European isn’t nearly as excited and instead dampens the energy coming east. These seemingly minute differences can make all the difference when it comes to the sensible weather that may (or may not) impact your weekend plans. If the European is correct, this is a rather non-event, locally. However, should the GFS idea be correct, this will be a widespread Ohio Valley snow event that’ll require gassing up the snow plows…
The European model weakens the energy coming east needed to fuel a more substantial storm Friday into Saturday.
The GFS model bundles the upper energy and phases things- leading to a more significant wintry threat by Saturday.
Stay tuned as we’re still a few days out from having confidence needed to begin to sound the alarm. 😉
In the longer range, tonight’s data continues to head in the direction where winter will make up for lost time to close January and head on into February. Delayed, but not denied…
Permanent link to this article: https://indywx.com/2019/01/07/weekend-threat-subtle-differences-make-all-the-difference/
Dec 26
Rain Arrives Tomorrow…
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Permanent link to this article: https://indywx.com/2018/12/26/rain-arrives-tomorrow/
Dec 22
Pre-Christmas Weather Rambles…
I. While we certainly aren’t talking about significant weather events between now and Christmas Day, there will be a couple of impulses of upper level energy that may be just strong enough to produce snow showers and flurries at times. We’re tracking (2) weak disturbances that stand a chance to get a couple of snow showers going Sunday evening and again Christmas Day. The one on Christmas, itself, will be a bit stronger and may have a shield of more organized precipitation- likely that would start as wet snow before transitioning to rain before ending.
II. A much stronger storm system will wrap up to our northwest Wednesday night and Thursday. We’ll notice an increasingly strong southerly breeze during this time period and rain will be on the increase as we progress through the day Thursday. The trade-off? Highs between 55° and 60° to close the week- though those temperatures may actually come Thursday evening before cooler air begins to slip in here during the day Friday.
As things stand now, both the GFS and European models, courtesy of Weathermodels.com, aren’t overly excited on rainfall amounts with this storm system, but I think they’ll trend wetter as time goes on. We’ll continue to forecast amounts between 0.50″ and 1″.
III. All attention is squarely focused on a significant pattern change that takes shape as we head into the new year. As mentioned in previous posts and discussions, the transition is likely to be a stormy one, but it’s far too early to talk precipitation types. A combination of ingredients appears to be aligning to create a colder than normal (and potentially significantly so) pattern at the traditionally coldest time of year (mid-Jan).
In the more immediate term, we note the latest GEFS showcases a classic “horse shoe” block that will favor a wintry regime across the east to open the new year- thanks to Tropicaltidbits.com.
Permanent link to this article: https://indywx.com/2018/12/22/pre-christmas-weather-rambles/
Dec 16
“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/2018/12/16/pulling-the-curtain-back-on-the-late-december-pattern/
Dec 13
Damp At Times Into The Weekend; Christmas Pattern Change?
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Permanent link to this article: https://indywx.com/2018/12/13/damp-at-times-into-the-weekend-christmas-pattern-change/
Nov 26
Cold Gives Way To Milder Air And Rain…
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Permanent link to this article: https://indywx.com/2018/11/26/cold-gives-way-to-milder-air-and-rain/
Nov 20
Quiet And Chilly Thanksgiving…
Quick update on the go with what will be a chilly, but dry Thanksgiving holiday. Our next storm will begin to impact the area Black Friday.
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Permanent link to this article: https://indywx.com/2018/11/20/quiet-and-chilly-thanksgiving/
Nov 18
Looking At The Thanksgiving Week Forecast And On Towards Early December…
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Permanent link to this article: https://indywx.com/2018/11/18/looking-at-the-thanksgiving-week-forecast-and-on-towards-early-december/