Arctic Cold to Abruptly End in Mid February, Return in March

It's looking like we will see the recent Arctic cold come to a quick end in mid-February.

The image above shows the GFS Ensemble 500mb height anomaly forecast for February 17th over the western Pacific. We see strong ridging present over Japan and much of eastern Asia, with another swath of positive height anomalies displaced further east to the south of Alaska. Using the idea that a storm system in Japan can signal a storm in the US 6-10 days later, we can find that this strong ridge over Japan should also come back to haunt the US 6-10 days later. That would place warmer and quieter weather over the nation in the February 23-27 period. Considering high pressure should be affecting Japan both before and after this February 17th forecast graphic, it would be reasonable to think that this warmer/quieter weather may extend into early March, as well as closing out the last week or so of February.

This warm trend can be seen by the Earth System Research Laboratory's (ESRL) Analog Temperature 8-14 day outlook, as is shown below:

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As we move into early March, it looks as though we will be heading into new phases of the Madden Julian Oscillation (MJO). Looking at the March 8th MJO OLR anomaly forecast, in the middle panel of the left side of the images above, we see deep blues spread out across the waters to the southwest and southeast of India. These deep blues represent enhanced tropical convection, and it also means an active phase of the MJO will be evolving.

If we compare that March 8th forecast image to the MJO OLR Composite image from the Australian Bureau of Meteorology, we see that the blues on the forecast image line up the best with MJO Phase 2 and MJO Phase 3, which are seen as the second and third images down from the left-hand side of the panels above. If we look at the low amplitude Phase 2 MJO (which guidance predicts we see when the MJO does enter Phase 2 before transitioning to Phase 3) 500mb height anomaly image below from scotlandwx.co.uk , we find that deep negative height anomalies are favored over the East US, resulting in colder than normal weather. The troughing in the Gulf of Alaska remains present, with suppressed ridging over the north central Pacific Ocean. Long range ensembles favor this type of set-up for the middle-late portions of February, and it's very possible this continues into March. To clarify, while the set-ups may be similar from mid-February onward, I currently only expect warmer weather for the mid-late parts of February due to East Asian ridging. Beyond that period, into early March, indications of East Asian ridging dissipate, allowing cold weather prospects for early March to flourish.

Low amplitude Phase 2 MJO 500mb height anomaly composite

The 500mb height anomaly composite for all amplitudes of a Phase 3 MJO also favors some cooler weather in the East US, though the cold is more restricted to northern parts of the nation.

So, let's sum it all up.

•We are looking at warmer weather over the United States in the closing week of February, possibly extending into the opening days of March.

•The pattern after the early-early March warm-up looks chillier, with a potentially favorable MJO (keyword is potentially due to the typical long range forecast caveats and inaccuracies) and favorable signs from East Asia after ridging moves out.

Andrew

February 13-15 Potential Snowstorm

It looks like we may see a winter storm along the East Coast in the February 13-15 timeframe.

The GFS model indicates we will see a negatively tilted trough work its way down into the Northeast and Mid-Atlantic around Valentine's Day, in the midst of an established northwest flow regime. We see this regime set up as a result of storminess over the Gulf of Alaska, and a suppressed ridge in the West US.

The GFS model wants to take what appears to be a strong clipper system eastward into the Northeast in association with the trough we saw in the image above. The clipper then transfers to the coast on the morning of Valentine's Day, resulting in snowfall for the interior Northeast. Rain looks to be the preferred precipitation type on this model solution for coastal regions. Since this is still in the long range GFS, none of this should be taken verbatim- we're trying to pick out the general pattern that could then yield a winter storm. In this case, the northwest flow with an Alberta Clipper transferring offshore seems like a rather likely scenario if the opportunity arises for a clipper to form around Valentine's Day.

The ECMWF has a similar situation, with the 500mb height anomaly forecast highly indicative of the northwest flow regime we discussed. The suppressed ridge and storminess over the Bering Sea is clearly evident, though the ridge in the Southwest is so suppressed the flow is borderline-zonal in that area. Nonetheless, we can still see the northwest flow alignment across the contiguous United States (CONUS).

The ECMWF model has the storm system impacting the Mid-Atlantic primarily, before heading off out to sea, only scraping coastal portions of the Northeast. This solution would lay down snowfall in the Mid-Atlantic states of North Carolina, South Carolina, West Virginia, and Virginia. This particular ECMWF model forecast lays down over 13" of snow in these areas, but these amounts would be better off cut in half for more accurate (but still slightly overdone) amounts.

So why will this storm hit the Mid-Atlantic and Northeast?

The answer lies in the jet stream and 500mb level. Here in the jet stream, we see the storm system well defined in the Central US on the 12th of February. If we look closely at the winds surrounding the jet stream, we see a jet streak (area of higher winds within the jet stream) positioned to the right of the trough. Typically, when a jet streak is to the right of the trough, the trough will lift north. This same principle applies here, as we then see the trough lift north and east, tilting negative as it does so to indicate the storm has reached maturity.

The 500mb level, shown two images above this jet stream graphic, also supports the storm lifting northward. We see a strong ridge of high pressure located well offshore of the East Coast of the US, which would nearly assure the storm lifting northward. Additionally, the trough beginning to tilt negatively in the East US would help out with the storm wanting to move north.

So what can we establish right now?

-The synoptic pattern looks favorable for a winter weather event in the East Coast, thanks to an evolving northwest flow pattern.

-A potential storm system is being modeled on forecast guidance that may impact the East Coast of the US.

-If a storm system does form in the United States, it looks like it will be favored to bring snow to inland portions of the East Coast, rather than coastal regions.

Andrew

Valentine's Day Potential East Coast Snowstorm

I'm monitoring the potential for a Valentine's Day snowstorm.

Medium range model guidance is supporting the formation of deep negative height anomalies in the Gulf of Alaska, in stark contrast to the typical high pressure anomalies in that area that have given us the anomalously cold winter this year. The negative height anomalies will be helped out by strong positive height anomalies in the western Bering Sea and into the northwest Pacific. As a result of this highly meridional (wavy) pattern in the Pacific, it looks like we'll be seeing suppressed high pressure form in the Southwest US, which will lead us into a northwest flow set-up. The probability of this is enhanced by the negative height anomalies dropping down from Canada into the Northern US, indicative of colder weather in the areas north of the jet stream. The areas affected would include the Great Lakes, Midwest, Plains, Northeast and Mid-Atlantic, to name a few areas.

With this northwest flow would come increased chances for snowstorms for the Northeast, and it looks like we could see one of those storms around the Valentine's Day time period.

The long range GFS model shows heavy snowfall hitting the Northeast in response to a storm system moving away from the coast. The snowfall would likely be maximized along coastal regions, including Massachusetts, New Jersey, and the coastal portion of New York. The northwest flow pattern is clearly defined here, not only by the presence of a coastal storm, but also with the southeast-moving 1000-500mb thickness contours, where blues show colder weather and reds indicate warmer weather. The stray clipper system in Minnesota also alludes to the presence of that northwest flow.

While the GFS is obviously in its inaccurate long range forecast at this point, and there is every chance that this storm may not end up happening, I'm thinking the East Coast will see a shot at snowfall in the mid February time period. Whether it be an amplified clipper system that hits the coast and gives big snows to the Northeast, or a storm system crawling north from the Southeast, I'm liking the East Coast for the snowier opportunities come mid-February. The prevailing northwest flow, which model guidance is in good agreement on, would not support a Midwest, Plains or Ohio Valley major snow event. Alberta Clipper systems would be more likely.

Andrew

February 9-14 Potentially Significant Snowstorm

It's looking like we'll be seeing another snowstorm between the February 9-14 period, and some indications are that this could be a rather significant snowstorm.

Above, we see the 500mb height anomaly forecast for the evening of February 3rd. We see a strong trough digging southeast towards Japan. The arrow I drew gives you an idea of where the storm system goes in the couple of days after this forecast image. The storm then continues to dig before it is a fully negative-tilted storm, indicating the system has reached peak maturity and strength. Then, the system cuts north, as the arrow shows you. Using Joe Renken's idea that a storm system over Japan correlates to a storm system in the United States 6-10 days later, we can project that a storm system will hit the United States around a February 9-13 time period. This fits almost completely inside the timeframe I put in this post, with the one day extension to February 14th brought in to account for any delays model guidances may encounter, since model guidance can have a bias that results in forecasts being too fast with storm systems.

The curve in the East Asian storm system suggests that the eventual storm system in the US may also curve north. This includes a variety of possibilities, including a Colorado Low storm, a Panhandle Hook storm, an Apps Runner storm, or even a Nor'easter.

Also supporting this potential storm system is the Lezak Recurring Cycle. The Lezak Recurring Cycle, or LRC, is a tool developed by meteorologist Gary Lezak that, in essence, can enable forecasters to predict the overall weather pattern months in advance. The gist of the LRC involves a cycling weather pattern that develops in October and November of each year; no pattern is the same from year to year. Around mid November, the LRC begins to repeat, meaning we start to see a similar weather pattern in mid November that we saw in early October. This means that the cycling pattern has begun, and it will continue to cycle on a regular (non-changing) 40-60 day interval for the next ~10 months before it dissipates over the following summer.

This season's LRC cycle is on a 57 day cycle length, meaning the weather we saw in December can be expected to "come back" as we enter February. The image above shows the surface condition map on the left and 500mb map on the right from December 14, 2013. If w extrapolate that date out 57 days, we come to the February 9th mark. As the 500mb map above shows, we have high pressure over the West Coast, with only slight ridging in the Southeast and the storm system easily working its way across the Plains. Based on the pattern I'm seeing to start February, I'm thinking a storm track similar to the one this system took in mid-December could very well be in the cards. If you read my February 4-6 posts, you may recognize this storm, as I talked about how it would correlate with that storm system. It seems I miscounted a bit, and the 57 day period from December 14th goes out to February 9th, rather than 7th. Therefore, this December 14th system looks to correlate with the February 9-14 storm threat.

Now, I named off a few possibilities for this system's track, which included a Colorado Low track, a Panhandle Hook track, an Apps Runner track or a Nor'easter track. If the LRC is to be believed, we could narrow down the track possibilities to a Colorado Low track or Panhandle Hook track. It's too far out to nail down exact probabilities of these tracks, but the two aforementioned tracks may be more likely than the other two tracks.

The 12z GFS actually showed a solution not unlike the one being printed out by the LRC and East Asian correlation.

TropicalTidbits

In the 12z GFS model, we saw a storm system dig southeast into the southern Plains before going negative tilt, and eventually closing off as it began to move north. This forecast scenario looks rather similar to the one we're seeing with the February 4-6 system, though this forecast is certainly much more ominous than the February 4-6 forecast.

Just for a little eye candy, here's the snowfall forecast from that 12z GFS model run. Please note this is not my forecast, nor do I endorse it- just showing you what this beast could become if it really is as strong as projected (though the probability of such an occurence working out is rather low).

Andrew

February 4-6 Major Snowstorm

There will be a major snowstorm over the February 4-6 time period, which has the potential to drop up to a foot of snow.

The GFS model, whose 87 hour snow projection is shown above, indicates we will see heavy snowfall in the 8-12" range across easterk Kansas, southeast Nebraska, northern Missouri and into Iowa. Amounts then taper off into the 3-6" range in Illinois, before ramping back up in the Northeast, where amounts over 12 inches are possible. The GFS model has been consistent with this storm thus far, and with the storm only a couple of days away, it looks like this is the track that is more likely to work out. The snow amounts have moved north of the far south storm tracks that we saw days earlier, and this north shift was expected, per earlier posts I put out.

The NAM model is much more enthusiastic with snowfall, laying down 6 to 10 inches of snow in Kansas, Nebraska and much of Missouri before pounding the Lower Great Lakes region with over 12 inches of snow. Northern Indiana appears to be heading for 20 inches of snow if this model is to be believed! However, the NAM model had previously been showing a far northwest solution, so additional nudges south may be anticipated. I do expect snowfall amounts will be lowered in future forecasts, as the NAM model is notorious for over-estimating snowfall. The stripe of snowfall extending from Texas to the Mid-Atlantic is not associated with this storm.

Because the storm system has not come ashore yet, slight changes in storm track and snowfall amounts can be anticipated. We should begin to see a solid model consensus tomorrow or tomorrow evening, when the system comes onshore and the balloon network can get fresh data from the storm.

Andrew