Category: PNA

Contradiction In Model World…

After the wet, windy, and chilly spell of weather this week, we have contradicting signals in model world for what lies ahead as we flip the page into November. With so much “noise,” we don’t think it’s wise buying whole-heartedly into any paticular idea for November just yet.

Here’s the plot line…

The PNA trends negative in the mid range and would argue for eastern ridging, and associated warmth.

NegativePNA

Sure enough, we see model data (GFS ensembles shown here, courtesy of Weatherbell) going towards what a negative PNA should promote- eastern ridging and an associated warmer than normal time.


BUT…not so fast, as the latest MJO forecast keeps things in Phase 2 for a while and doesn’t show near the amplitude it did only a week ago in moving into Phase 3.



As shown above, Phase 2 argues for chill across our neck of the woods, with Phase 3 being much milder.

Let’s watch things unfold this week and revisit this post a bit later as a follow-up with what lies ahead. There’s never a dull moment in this business.

Permanent link to this article: https://indywx.com/2015/10/26/contradiction-in-model-world/

Colder Air Arrives Late Week…

A tranquil and warm start to the week (today and Monday) will take a bit of a hit for mid week as the first of two waves of cooler air…

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Permanent link to this article: https://indywx.com/2015/10/11/colder-air-arrives-late-week/

Post From The Road…

We’re en route back from a phenomenal family vacation along the world’s most beautiful beaches along the Florida panhandle. This was my view for the past week.    Too bad…

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Permanent link to this article: https://indywx.com/2015/09/26/post-from-the-road/

Monday Morning Weather Rambles…

September is still running much warmer than normal, despite the recent well below average regime. See the temperature anomalies over the past (7) days:    and the month-to-date:      …

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Permanent link to this article: https://indywx.com/2015/09/14/monday-morning-weather-rambles-3/

Cooler Times Ahead By Mid Month?

Summer sure doesn’t appear to be letting go anytime soon as our recent 7-day outlook suggests, but there are indications that our unseasonably hot and humid regime may take a back seat to the refreshing taste of fall in about 10 days.  The big “tip of the cap” towards the cooler pattern?  The PNA, or Pacific North American pattern, shifting from negative to positive.  As shown below, both the European (top) and GFS (bottom) highlight the PNA shift to positive.

Screen Shot 2015-09-02 at 7.58.03 AMA positive PNA favors eastern troughiness and an associated cooler than normal regime over our neck of the woods.

PositivePNASure enough, models are trending towards a much cooler direction for week 2.

Screen Shot 2015-09-02 at 7.54.04 AM

Screen Shot 2015-09-02 at 7.53.54 AM

Screen Shot 2015-09-02 at 7.54.14 AMIt’ll be fun to watch things unfold.  For now, if you’re a fan of summer weather, be sure to enjoy the next week, or so, as things appear to be changing for the much cooler side of things around the 10th (give or take a day or two).

Permanent link to this article: https://indywx.com/2015/09/02/cooler-times-ahead-by-mid-month/

A Word On The Longer Range; Steady As She Goes…

We wanted to touch briefly on the longer range weather pattern as we’ve been answering questions this weekend out there concerning what lies ahead. Ultimately, the good Lord above is the only one who knows tomorrow and this idea we have very well may be the wrong one. However; we still see a lot of winter in this weather pattern. The combination of below average snowfall to date, combined with milder air the past 24 hours has led some winter lovers into a panic. Despite the past 24 hours, let’s remember where we are for the month of January through the first half:

image

Now let’s compare this to the infamous January 2014:

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So far, this January the cold is more widespread across the nation. Additionally, through the first half of January, IND is actually running colder than last January. Many remember the brutal cold following the major winter storm early last January. Let’s also remember that a few days after that snow and cold we were dealing with much milder air and rain- a bonafide January thaw.

That brings us back to the present and our current January thaw. Looking back through the record books indicate even the coldest Januarys on record have “thaws.” What’s perhaps more impressive is that the end of this year’s thaw appears to be seen really before it even begins.

There are so many different drivers trying to take the wheel this winter it, admittedly, makes for an incredibly challenging time of things forecasting. That said, should we see the “stars align” (negative AO, negative NAO, positive PNA) in the coming weeks, this is the type scenario that could carry winter deep into spring.

In the shorter term, as of now we see no reason to abandon the idea the cold reloads to close January and open February. It’s possible that some weather outlets lean heavily on particular model runs and base their mid to long range forecast accordingly. While we agree you have to supplement some of that data into your mid and long range forecast, this is the type pattern than can make for risky business putting all the eggs in one basket.  (We also suggest any outlets leaning solely on operational and ensemble output are in need for a serious dose of dramamine). Instead, we prefer a blend of the above with the foundation being a combination of a nearly ideal SST profile for wintry times continuing and big-hitter analogs. It must also be noted that we have to keep the current AO/ PNA state in the back of our mind.

Speaking of those teleconnections… The current AO and PNA leave a lot to be desired for winter lovers in the longer range:

image image

That said, it should be noted the first two weeks of January cold was in the face of teleconnections that screamed of a warm pattern and a MJO phase that was also mild.

Perhaps the bigger driver here is the surface temperature profile in the PAC and ATL. Also note the modoki El Niño.

IMG_2167.PNG

That warmer water sitting across the northeast Pacific Ocean promotes ridging into the PAC NW and AK.  In return the upper level winds tap available arctic air and send it southeast (see the first two weeks of January).

In the mid range, ensemble data is bullish on this aforementioned pattern returning after the very brief January thaw.

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The sensible weather that should result the upcoming 10-12 days?  An active pattern and one that’s very challenging with that northwest flow (we’ll be on clipper watch), biased colder than average.  In fact, the GFS ensembles aren’t too shy about eastern cold week 2.

gefs_t2m_mean_noram_d8_16

Let’s watch things unfold in the coming couple of weeks.  Make it a great day and GO COLTS!

Permanent link to this article: https://indywx.com/2015/01/18/a-word-on-the-longer-range-steady-as-she-goes/

Brrrrr…. Cold Pattern Continues

Many across the Lower 48 are running MUCH colder than average this morning. Take a look a temperature departures from normal this morning: Mind you this is in the face…

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Permanent link to this article: https://indywx.com/2014/12/31/brrrrr-cold-pattern-continues/

Shame, Shame, Shame; Humble Pie Never Tastes Good…

Shame, shame, shame…That’s all I can say when we deal with a blown opportunity for snow with a surface low that tracks in an ideal position for the white stuff,…

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Permanent link to this article: https://indywx.com/2014/12/21/shame-shame-shame-humble-pie-never-tastes-good/

A Look At Where We’ve Been And Where We’re Going…

December so far has been a battle between the cold northern tier and warmth south. The so-called “battle zone” has been located over our neck of the woods and lead…

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Permanent link to this article: https://indywx.com/2014/12/09/a-look-at-where-weve-been-and-where-were-going-4/

Major Storm Brewing This Weekend, But Details Are Murky…

During the late summer and early autumn months we were trying to look at the big picture and potential drivers in the overall weather pattern for the upcoming winter and openly admitted the challenges that were ahead.  Here we are now into the second half of December and a much colder and snowier-than-average month is a virtual lock at this point.  Furthermore, consider this has all taken place without the presence of a favorable NAO or PNA.  Sometimes you have to look for other drivers in a pattern- in this case, the EPO, as well as a growing early fall snow pack across the border to our north.  Additionally, we made mention of the likelihood of a southeast US ridge periodically making itself known through the winter of ’13-’14.  You can read all of our thoughts posted earlier this fall here, or by clicking the Thoughts On Winter ’13-’14 page above.

As we look ahead towards the upcoming wintry challenge, we’re confident of the overall pattern, but the sensible weather that’ll ensue is still up for great debate.  “Gut” tells me central Indiana will be looking at a rain to freezing rain scenario, but this is far from set in stone, and sometimes forecasters who go simply off their instinct can get burned.  The pattern is one that (once again) will feature a pressing arctic front against resistance from the southeast US ridge.  With this type of scenario, I would advise against looking at each and every individual operational model run, but instead invest time studying the ensembles- an average of several multiple model runs as opposed to just one operational model run.   I can guarantee a variety of wild solutions ahead in the days to come, based off the operational runs. (Heck, just the past 24 hours have been reason enough to have the dramamine on hand :-)).  That said, let’s take a look at the latest GFS and European ensembles, two models that we rely heavily on in the mid range weather pattern.

First, the GFS, valid Saturday through Monday.

f120f144f168

Now, here’s a look at the latest European ensembles (left), again valid Saturday-Monday.

Geopotential32at32500hPa_North32America_120Geopotential32at32500hPa_North32America_144 Geopotential32at32500hPa_North32America_168

So what do all of these cool maps tell us?  Simply put, that “wintry mischief” is brewing for the weekend.  That much we know, but the details have to be ironed out.  It’s likely heavy snow and a significant ice storm looms for some of the Mid West and Ohio Valley for the upcoming weekend.  Is that Indianapolis or Chicago?  Perhaps in between?  It’s too early to know.  Additionally, in the “warmer” sector, heavy rains are likely to combine with an impressive early season snow pack for some to lead to flooding concerns.

A couple of additional items to note. Many times at this stage in the game (still 5+ days out) with this type of pattern, forecast models really struggle with handling low level cold air.  Cold air is very dense and, in this type of set up, can easily drain much further east and south than forecast at this juncture.  Additionally, sometimes the modeling can put too much “umph” into the associated surface wave that moves along the arctic front resulting in a further north track than what may actually occur when the event draws closer.  Just something to keep an eye on as we draw closer…

Needless to say, it’ll be particularly important to keep a close eye on the developing weekend forecast as we move forward.  It’s likely folks in the Ohio Valley region have to deal with significant precipitation amounts in the Saturday-Monday time period, including rain, freezing rain, and snow.

Permanent link to this article: https://indywx.com/2013/12/16/major-storm-brewing-this-weekend-but-details-are-murky/

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