Category: NAO

Overwhelming Evidence On Mid Month Cold…

The step-down cold pattern early January is ongoing, but we’ve been clear with our thinking of even colder air invading around mid month (Jan 10th-20th time period). We wanted to…

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Warm Late Next Week; Active Times Loom For The 2nd Half Of December…

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Welcome To Meteorological Winter…

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Iron Bowl Saturday: December Rambles…

This is a special day in the McMillan house.  Iron Bowl Saturday only comes around one day a year… Needless to say, the Auburn flags have been on the vehicles since Wednesday, we’re decked out in our orange and blue, and game faces are on for this evening’s matchup.  WAR EAGLE!

As we get set to flip the calendar to December, we wanted to post some latest thinking.

Let’s take a look at the latest teleconnections.  As we’ve been talking, there’s a lot of “noise” in model land, including conflicting signals.  The positive NAO and AO argue for warmer than average conditions, while the positive PNA suggests chillier than normal times should prevail.

We wanted to post the latest model predictions of each teleconnections, courtesy of Weatherbell.com.  Additionally, courtesy of madusweather.com, here’s what each teleconnection “phase” would normally lead to in December.

NAO

Screen Shot 2015-11-28 at 10.55.21 AMNAOpos_12dec

AO

Screen Shot 2015-11-28 at 10.55.07 AMAOpos_12dec

PNA

Screen Shot 2015-11-28 at 10.55.34 AMPNApos_12decSimply based on the teleconnections, you would build a December forecast that would lean more warm than cold, as the short term positive AO and NAO should trump the positive PNA.  As we look at the month, as a whole, the AO and NAO are forecast to trend more neutral, while the PNA remains solidly positive.  Does this suggest colder air, relative to normal, would invade mid and late month?  – Certainly something to watch.

Additionally, the latest Southern Oscillation Index (SOI), has begun to take a negative hit.  This is after weeks of positive SOI values- relative to the base state.

Screen Shot 2015-11-28 at 10.47.52 AM

 

 

 

 

While it takes a while to impact the pattern, locally, this negative hit does suggest mid and late month could be a bit more interesting from a wintry perspective.  We shall see.

The CFSv2 remains very consistent on a warm month, relative to normal, particularly across the northern tier.

cfs_anom_z500_noram_201512_w3cfs_anom_t2m_noram_201512_w3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

While we can’t post the European weeklies here, the latest run suggests colder, and stormy times around Christmas week.  Now, we should also note the overall performance of the Weeklies hasn’t been as accurate compared to normal over the past few months, but it’s another interesting trend to keep an eye on.

The MJO will begin the month in Phase 3 before going into the “wheel house.”  All-in-all, we don’t get a “hat tip” from the expected monthly MJO forecast, with the exception of Phase 3 to begin (warm phase).

EMON_phase_MANOM_51m_full

Screen Shot 2015-11-28 at 11.53.45 AMTo sum up:  Long range forecasting is always a gamble.  Only the good Lord knows what the future holds.  That said, there are times when we feel more confident about our long range, monthly outlooks, more so than normal.

We’ll lean warmer than normal for December (+ 1.5 at IND), and this really plays into our Winter Outlook (slow start expected with the emphasis on the cold and snow mid and late winter), but that doesn’t mean we’re expecting a “boring” month.  Keep in mind November has been both warmer AND snowier than normal, with a very busy 2nd half of the month.

We’ll have plenty of challenges to handle as we rumble through the month no doubt, but we expect the positive AO and NAO to trump the positive PNA to start to the month.  As we progress into mid and late month, we’ll have to be on alert for potential impacts of that significant SOI hit to open the month.  We’ll also keep the Weeklies in check to see if the colder, stormy look Christmas week remains.  It’ll be fun, as always.

To close, here’s one more emphatic WAR EAGLE from our home to yours! 🙂

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Warm Up Coming…

After a long and cold winter, many are excited about hearing of the prospects of a warm up and first true taste of spring.

While the European data has totally bought in to the impressive “spring fling” next week, the GFS isn’t as excited of the potentially warmer times.  Case in point, the GFS and European couldn’t be in more different camps for mid and late next week.  Where the GFS has low/ mid 40s for highs the European has low/ mid 60s for highs.  What’s 20 degrees amongst friends?!

Wild model swings and disagreements are common when pattern changes are taking place.   While we might not get as warm as the Euro. would imply, it’s a safe bet we’ll be considerably warmer than the chilly GFS readings.

Note the AO and NAO strongly positive through the next 10-15 days.  This is the time of the year when these teleconnections can impact our region’s weather in the most significant way.  Both of these are warm signals taken at face value.

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Note the pattern flip to a “flat” ridge by Day 10, indicative of the milder times ahead.

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However, by Day 15 we notice the Alaskan ridge redeveloping.  This is NOT a signal for warm weather across our part of the region, as the steering currents would tap available cold air and direct it south into the Mid West and Ohio Valley.

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So, what do we take from this?  We’re going to warm next week without question.  While the extent of the warming is up for debate, the overall milder times for a 5-7 period is a good call at this point.  On the flip side, we’re not ready to buy into the idea that spring is here for good just yet.  The building Alaskan ridge by the end of Week 2 would imply a cold close to March, and potentially continuing into early April.

Another item to keep a close eye on the upcoming 4-6 weeks?  Those NAO and AO signals.  Should they remain predominately positive this time of year then it’ll be exceptionally challenging to get any sort of cold pattern to lock in for more than a day or two.

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