Category: PNA

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.

Days 3-8
Days 8-13
Days 10-15

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/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/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/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?

Recurving Super Typhoon Hagibis will promote reinforcing chill across our area next week.

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/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…

Forecast radar 11p Saturday.
Forecast radar 9a Sunday.

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/saturday-morning-rambles-10/