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Category: PNA
Permanent link to this article: https://indywx.com/2019/11/19/video-updated-short-term-and-longer-range-thoughts-into-early-december/
Nov 12
VIDEO: Looking Ahead To The Thanksgiving Pattern…
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Permanent link to this article: https://indywx.com/2019/11/12/video-looking-ahead-to-the-thanksgiving-pattern/
Nov 05
January-Like Cold Inbound Next Week; What Awaits Thereafter?
“Normals” for January includes highs in the middle 30s and lows in the upper 10s to lower 20s across central Indiana. Early to middle parts of next week are forecast to feature highs in the upper 20s to around 30 and lows in the middle 10s. Yes, these temperatures will challenge records as a truly impressive arctic invasion claims next week’s weather headlines.
A lot of this has to do with the sea surface temperature (SST) configuration across the northern Pacific. We’ve been focusing in on the warmer anomalies across the north and northeastern Pacific and tendency for this to drive a persistent ridge across NW NA since late summer. That persistent NW NA ridge leads to a persistent trough downstream and the associated cold pattern we’re now looking at. As our Winter Outlook suggests, we think this overall pattern repeats itself throughout the majority of the months ahead.
As we look more “immediate term,” what do teleconnections and the MJO tell us about the overall pattern moving past the middle of November? Well, to start, the highly amplified MJO is forecast to roll into Phase 7 around mid-month. This suggests the colder than normal pattern persists.
The EPO is forecast to remain negative while the PNA remains positive into and through the mid month period. Both argue for continued cold.
To no surprise, the latest long range data continues to drill unseasonably cold air south into our portion of the country and a large majority of the eastern portion of the Lower 48 in the Weeks 2-3 time period. Snow opportunities will undoubtedly follow with this kind of pattern.
Buckle up…
Permanent link to this article: https://indywx.com/2019/11/05/january-like-cold-inbound-next-week-what-awaits-thereafter/
Oct 17
Pattern Evolution Through Late October…
The teleconnections are aligning in a manner that favors a colder than average period of weather by late-October standards. Note the PNA trend positive while the EPO heads negative. The AO and NAO also follow suit.
The sum of all of the above should feature a predominant western ridge for late month with a persistent eastern trough- at times deeper than others.
Add in the fact that the MJO is anticipated to swing into Phase 2 and this further serves to increase confidence in the colder shift.
The models are focusing in on the colder close to the month and though specifics will continue to vary from run-to-run, the primary message that we want to convey is to expect a colder than average 2nd half of the month with an active storm track. As pops of more “winter-like” air get involved behind one or two of the late month storms, pre-Halloween flakes may fly across a portion of the Ohio Valley.
Given the pattern progression and anticipated teleconnection states, we think it’s wise to ensure the kiddos have a warm Halloween costume this year!
Permanent link to this article: https://indywx.com/2019/10/17/pattern-evolution-through-late-october/
Oct 14
Taste Of Winter Before Month’s End?
A cold front will whip through central Indiana Tuesday evening. Showers will accompany the frontal passage, but we still don’t anticipate much in the way of significant moisture across central Indiana. Heavier rainfall totals in excess of 0.50″ will likely fall across drought-stricken areas downstate.
Colder and blustery conditions will be with us Wednesday and Thursday, including wind chills in the upper 20s at times Wednesday morning.
A moderating trend will get underway this weekend as a gusty southwesterly breeze takes hold on the backside of retreating high pressure. This will lead to a couple of days of above normal warmth early next week (not quite done with the 70s just yet).
We’ll continue to monitor for a wet and stormy time of things Monday PM into Tuesday. The severe threat is to be determined and will require fine tuning as we push ahead over the next several days.
Once this area of low pressure and associated cold front blow through, colder air will arrive on gusty northwest winds by the middle to latter portions of next week.
This will set the tone for a rather significant colder shift as we get set to put a bow on the month of October. A secondary and more significant trough will descend into the region just after Day 10. With a developing negative EPO, positive PNA, and MJO heading for Phase 2, it’s time to start “beating the cold drum” a bit harder. In fact, latest 500mb charts would indicate there’s the potential of at least a little wintry mischief present to go along with the colder shift.
This should at least kick up the lake effect snow guns for the first time this season, and we’ll have to monitor things for the possibility of “backside” energy digging south at the base of the trough that would present the possibility of a little early season snow across parts of the Ohio Valley region as Halloween week nears…
Times, they are, indeed, ‘a changing…
Permanent link to this article: https://indywx.com/2019/10/14/taste-of-winter-before-months-end/
Oct 14
VIDEO: Frosty Midweek; Colder And Active Stretch Of Weather For Late October?
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Permanent link to this article: https://indywx.com/2019/10/14/video-frosty-midweek-colder-and-active-stretch-of-weather-for-late-october/
Oct 10
Cool 6-10 Day Period Ahead, But Then What?
A strong cold front will sweep through the area tomorrow and help usher in the coolest air so far this autumn. This will set the tone, combined with the recurving WPAC typhoon, for a chilly upcoming 6-10 day period, but what lies beyond this period later in the month?
We turn to a couple of our more trusted teleconnections for advice.
Note the PNA “bobbing” up and down through the medium range period, with more of a negative look around the 20th. This argues for a milder stretch of weather around that time. (Further out, we’ll keep close eyes on the PNA to see if a more consistent positive signal develops as we inch closer to November).
The EPO pops strongly positive mid month which, too, argues for milder times, locally. That said, similar to the PNA above, the EPO is trending towards a scenario that would present colder times as we rumble towards November. We’ll monitor for consistency.
To no surprise, given the two primary teleconnection drivers above (remember these can change as the seasons evolve), we see the pattern set to turn milder just beyond Day 10. Note the strong agreement between the European, Canadian, and GFS ensemble data below.
Permanent link to this article: https://indywx.com/2019/10/10/cool-6-10-day-period-ahead-but-then-what/
Oct 05
Saturday Morning Rambles…
I. Our Saturday will get off to a stunning start. Despite some patchy fog here and there, look for plentiful sunshine and chilly temperatures in the low-mid 40s rising into the low-mid 70s for afternoon highs with increasing clouds.
II. Those increasing clouds will deliver showers by tonight across central Indiana and then more concentrated heavier rain downstate Sunday evening into the predawn Monday. Southern Indiana is needing a good soaking in a bad way and this system will at least help things slowly begin to improve…
Rainfall totals with this system across central Indiana should accumulate to the tune of 0.20 to 0.40 for most with heavier amounts approaching 1” across the IN-KY border.
Note this is where things are driest across the state per Thursday’s drought update.
III. Our next storm system will swing through here late in the work week. We’re timing Thursday PM into early Friday for a round of showers and potentially gusty thunderstorms as a cold front pushes through.
Behind this boundary, the coldest air of the fall so far will blow into town. We’re continuing to think many of the area can expect the first frost of the season next weekend.
IV. As we look ahead, it’s time to start putting more stock into other tools in the box. Case in point, the MJO is showing signs of less amplitude over the upcoming couple weeks followed by a strongly positive PNA. This supports colder signals in the period. We’ll dig in further in the days ahead.
Permanent link to this article: https://indywx.com/2019/10/05/saturday-morning-rambles-10/
Oct 04
VIDEO: Welcoming An Autumn Like Feel; Fairly Active Pattern In The Week Ahead…
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Permanent link to this article: https://indywx.com/2019/10/04/video-welcoming-an-autumn-like-feel-fairly-active-pattern-in-the-week-ahead/
Sep 23
Something Doesn’t Jive…
I want to give a couple examples of significant conflicting signals- both short and long-term. The end result is a situation where long range, climate, and seasonal models are likely to have a very tough time not only in the medium to long range (2-4 week period), but thinking seasonally, as well (winter and next spring).
Short-term
To start, let’s look at the EPO. While strongly positive at present, both the EPS and GEFS pictured below take the EPO, or East Pacific Oscillation, negative in the coming couple of weeks.
A negative EPO pattern favors a trough across the eastern portion of the country, especially here in our neck of the woods, with western ridging.
All well and good, right? WRONG. The MJO, or Madden Julian Oscillation, is forecast to stall out into early October in Phase 1.
This time of year, Phase 1 argues strongly for eastern ridging and well above normal warmth while the western portion of the country can experience early wintry conditions.
Talk about contradiction! That’s what makes weather so fun and fascinating. Expect to be humbled often and to always learn! At various times of the year, select teleconnections can mean a lot more than other times of the year. For example, during the summer and fall, we lean heavily on the EPO, PNA, and MJO (if amplified). During the winter and spring, it’s important to take into account what the AO and NAO have to say. It’s important to know when to “pick and choose” when to use particular teleconnections… Furthermore, the various MJO phases (1-8) mean drastically different things at different times of the year. While lovers of chilly fall conditions have grown to hate an amplified Phase 1, they have to love it come winter (shown below). Just look at that difference!
Before jumping ahead to another example of “contradicting signals,” we’re confident the amplified MJO Phase 1 will carry the day through the short to medium range period. Note the strong agreement between the EPS and GEFS below with respect to temperature anomalies in the 6-10 day period.
With that said, there will be challenges within (the big difference as early as this weekend between the GFS and European operational data). A lot of that has to do with the “fight” between the EPO and MJO to take control.
As all of this unfolds across the East, the west will begin to cash in on early winter. Well below average cold and snowy conditions will begin to make headlines over the weekend into next week across not only the Rockies, but some of the low ground, as well. Should the MJO swing into Phase 2 (and I think it will towards mid-Oct), then watch out. We’ll be looking at a rather significant shift towards a much colder feel- and it’ll sting even more so with the late season heat over the better part of the next couple of weeks.
Flipping the page to winter (remember, our prelim. winter outlook will be posted later this week) and the contradiction continues. Upon looking at the current SST configuration, one could easily argue we’re talking about a La Nina winter unfolding ahead.
Meanwhile, the current SOI would suggest we’re in a moderate El Nino.
If you think this can’t wreck havoc even on the short-term forecast pattern, think again…
To close, while the conflicting data can create headaches at times, it’s more fascinating than ever trying to sift through the data and build our forecast(s). It’d be wise to expect more wild swings ahead- leave it to us to try and minimize the impacts of those swings in your day-to-day personal and professional lives. Accordingly, it’s also ultra-important to factor in additional items, such as solar and PDO into the equation for the upcoming winter.
Speaking of, without giving too much away, if I’m a winter weather fan (and I am), I wouldn’t worry in the least about the current warmth… 😉
Permanent link to this article: https://indywx.com/2019/09/23/something-doesnt-jive/