January 24-28 Potential Apps Runner / Nor'easter Winter Storm

There is the potential for an "Apps Runner" or Nor'easter winter storm around January 24-28, as a storm begins to traverse the Bering Sea in a favorable position.

This is the ECMWF 500 millibar anomaly forecast for the afternoon of January 5th, the day this post was published. You can see the deep negative geopotential height anomalies over the southwestern portion of the Bering Sea, and I drew a line outlining a rough track of where this storm system is projected to go in the next few days. Around January 6, the storm begins to cut north across the central/eastern Aleutian Islands, and then turns a little northwest to swirl in the Bering Sea. This is a telltale sign that we may be in for an Apps Runner or Nor'easter winter storm, as Joe Renken's Bering Sea Rule describes.

The Bering Sea Rule states that by watching storm systems make their way across the Bering Sea, one can identify where and when a storm system will show up in the United States. The general timeframe is 17-21 days after a storm appears in the Bering Sea, a storm will appear in the United States. This rule is already in use with the January 17-21 potential Colorado Low, and now it looks like the Eastern US might encounter some stormy weather if the Bering Sea Rule verifies correctly (which it has, when used previously).

The storm in the Bering Sea skirts in the southern portion of the waters across the January 5-6 time period, before cutting north on the January 6-7 time period. If we extrapolate that time frame 17-21 days out to use the Bering Sea Rule, we end up with roughly a January 24-28 period that we should watch for a potential winter storm. The reason I am labeling it as a possible Apps Runner or Nor'easter is because of how far east it cuts north. Joe Renken indicates that the further west storms cut north in the Bering Sea, the further west they end up 17-21 days later in the United States. In this case, our storm system here cuts far enough east that an Apps Runner or Nor'easter scenario does seem viable. The Bering Sea system is also displaying traditional characteristics of a Nor'easter scenario, where the storm moves in the southern waters of the Sea before cutting north quickly. A Nor'easter forms in a similar fashion, where the energy traverses the Southern US before shooting north along the East Coast.

To sum up:
There is potential for a winter storm over the January 24-28 time period, and indications are it could affect the Ohio Valley via an Apps Runner, or the Eastern Seaboard by way of a Nor'easter storm system.

Andrew

January 17-21 Colorado Low / Panhandle Hook Winter Storm

This is an update to the previous January 17-21 Potential Colorado Low/Panhandle Low Winter Storm post. Everything remains intact with this storm, and now the GFS is biting.

The following is copied from my December 27 post on this storm.

This image above from the Weather Prediction Center (WPC) shows the mid-level pattern over Alaska on January 1st. There are two systems marked on here; one storm system is over Alaska, as the dip in the height contours shows, and another storm is marked by the red 'L' just offshore of far eastern Russia. We're going to be watching the red 'L' for this storm system. Model guidance sees this storm cutting north over the western Bering Sea, and this is where we employ Joe Renken's Bering Sea Rule. The Bering Sea Rule states that when a storm moves through the Bering Sea, a storm system then moves through a portion of the United States 17 to 21 days later. If we see this system cutting north in the western Bering Sea around the December 31 - January 1 timeframe, we can then predict a storm system to cut north in the US as well 17-21 days later, which brings us to the January 16-22 time period. Because the storm is projected to cut north in the western Bering Sea, Joe Renken does believe that this signals a Great Lakes Cutter system around the 20th of January. Other subjects I will discuss below lend additional credibility to this timeframe laid out, as well as the predicted track of the storm.

The following MJO OLR portion is copied from my previous December 23 post on this storm, because the information remains valid.

The Bering Sea Rule isn't the only long range piece of guidance we can use to detect a potential storm. Here, in a CFS four-member ensemble forecasts developed by Kyle MacRitchie, we see the long range projection of the Madden-Julian Oscillation, in its eight-phase phase space diagram. Using this graph, we see that the MJO is projected to enter Phase 5 around December 27th, which all ensemble members agree on. Now, we'll take a look at the Outgoing Longwave Radiation (OLR) composites in the mid-latitudes for a Phase 5 MJO.

This MJO composite, developed by Nicholas Schiraldi, shows OLR anomalies in the 30 day period before and the 30 day period after the MJO hits Phase 5. In this case, negative lag days on the left side of the image show the number of days before the MJO gets to Phase 5 territory, while positive lag days on the left legend depict the number of days after the MJO hits Phase 5. We can substitute the lag day of 0 for December 27th, as that is when the CFS forecast above predicts we will get into that Phase 5 MJO. Looking ahead, we will ignore the red circled portion (that is for an upcoming post) and will instead take a look at the black circled part of the graph, where you can see blues shaded in. A look at the longitudes at the bottom of the image tells us the strongest negative OLR anomalies will be centered between the 85 West and 100 West longitude lines. If we put that together with the indication that this OLR anomaly chart is valid for latitudes between 55N and 40N, we find that the latitude lines cover the entire United States from Canada to Mexico, while the 85W and 100W longitude lines cover the US from roughly the Central Plains to the Great Lakes. If we clarify that negative OLR anomalies mean stormy weather, and observe that the circled blues are moving north and east, we can deduce that a Phase 5 MJO results in a storm system crossing the US across the Plains, Midwest and Great Lakes in roughly a northeast (or even east-northeast) direction. If we glance at the lag days on the left for when this storm would occur, we find that the circled blues encompass lag days of +17 to +25, meaning the storm would hit anywhere in a 17 to 25 day timeframe after the MJO hits Phase 5. 17 to 25 days after the projected December 27th arrival of the MJO at Phase 5 puts this potential storm system in the January 15-23 period. Now, in order to cut down on the large timeframe, I decided to shorten the positive lag days to cover the strongest negative anomalies only, which gave me a projected storm timeframe of January 18-21.

So we now have two timeframes for a potential storm system. The Bering Sea Rule gives us a timeframe of January 16-20, while the MJO OLR Composites give us a broad timeframe of January 15-23, which I shortened to January 18-21. If we put those two dates together, we end up with a broad-brush timeframe of January 15-21, which covers all dates outlined by either one or both indices. If we shorten that January 15-21 period to only include dates that both indices highlight, we end up with a January 18-20 timeframe for this potential Plains/Midwest/Great Lakes storm system.

How do we know the track of this storm?

Well, we've already deduced from the OLR charts that the longitude and latitude markings would strongly suggest a Plains/Midwest/Great Lakes storm system, moving northeast as it crosses those regions. With that in mind, I took a look at a device created by Larry Cosgrove and found two plausible storm tracks.

Image created by Larry Cosgrove.

The first track possible is a Panhandle Hook (A) system. We can see that this system fits the bill that was outlined by the OLR charts. It originates in the Plains and move northeast through the Midwest and Great Lakes. These systems tend to bring heavy wintry precipitation to the Midwest, Great Lakes and upper Plains, and, if all goes right, these systems can attain massive amounts of moisture from the Gulf of Mexico to enhance these wintry precipitation prospects.

Image created by Larry Cosgrove.

The second track that also fits the bill is a Colorado Low (A). The system originates in the Plains and then moves northeast across the Midwest and Great Lakes before progressing into Canada. The MJO OLR charts confirm that this storm is also a possibility, and the last time I used the MJO OLR charts to make a long term prediction, the results were spectacular. Because this potential event is still about a month away, we don't know how the teleconnections will react to possibly force this storm in a different direction than what the MJO OLR composites predict will happen. (End copied portion from Dec 27 post)

The latest 18z GFS has actually caught onto a storm in this timeframe, with the above image showing a storm valid on January 18th. I can guarantee you that this forecast will change, but it is interesting that we have seen the GFS bite on this idea of a storm system.

I expect we will see additional solutions with a storm around the 20th come about, just because of all of the factors supporting a storm in this timeframe. There are model solutions about a storm system just a few days before this projected storm system, and while they would technically fit into the MJO OLR Composite idea of stormy weather in and around the January 17-21 time period, I still believe the timeframe currently set forth will come to fruition.

Andrew

Long Range Outlook: January 1, 2014

ECMWF (left), GFS (center) and CMC Long Range 500mb anomaly forecast

Long Range Discussion
January 1 2014

Multi-model guidance above for the 8-10 day period shown is in average agreement, with highest disagreement area over northern Canada into Greenland, leading to additional disagreement over the Northeast United States. Model confusion revolves around whether to allow development of strong low pressure over Greenland, which would then help chances for ridging out towards the Northeast and East Coast. ECMWF and GFS are in the "best" agreement of the three model suite, with the ECMWF centering the anomalous low pressure west of Greenland and the GFS strengthening said low pressure system and placing it south and east of Greenland. The difference in location will affect the large-scale weather pattern, with a more compact solution with that upper-latitude low pressure system as exhibited by the ECMWF leading to stronger ridging along the East Coast. On the other hand, if the system is to be placed east of Greenland, the low pressure would be elongated from the Bering Sea out to the waters east of that land mass, and that would temper ridging prospects in the East US.

Model guidance is in good agreement on ridging keeping a chokehold on the Arctic Circle, which will prohibit reformation of the polar vortex across that area, and thus will keep the risk for cold weather across lower latitudes rather high. All modeling systems are also in agreement on ridging appearing over the southern Gulf of Alaska and into the north central Pacific, and we also find a consensus among the guidance with deep low pressure over the Bering Sea into Alaska. Now, for the long range that we are watching over for this time period (8-10 days out), this means we will be seeing a pattern that will most likely keep out extreme cold weather like we will see to kick off the upcoming workweek. In the long-long range, this somewhat-anti-cold pattern will flip over.

This map from Michael Ventrice shows 200 hPa velocity potential anomalies over a time-longitude graph. Blues and dashed ovals indicate the presence of enhanced convection (and thus a Madden-Julian Oscillation / MJO wave), while solid ovals and warmer colors signify a suppressed MJO wave. Taking a look at past, present and future conditions, we see how the MJO wave has been progressing across the Indian Ocean and towards the central Pacific for some time, oscillating through the various phases of the MJO. Some dynamical models were giving off a false "dead MJO" signal, where the guidance indicated the MJO was too weak to track. In reality, this was another body of enhanced convection firing over South America. This dual-placement of tropical convection is referred to as a "Wave 2" pattern, due to the two waves of active convection. In reality, the MJO signal was always oscillating around the phase space, as the progression of the MJO wave in the graph above shows. Now, as we look ahead, the GFS projects the MJO wave to continue pushing east, to be centered at the ~170E longitude mark around January 10th. This is a classic forecast of the MJO pushing through Phase 6 (centered around 160E), and Phase 7 (centered around 180). Model guidance should see an intensification of either the zonal flow across the US or ridging on the East Coast, as ridging in the US is common in a January Phase 6 event. A January Phase 7 event results in significant ridging in the West that will then transition us into the mid/late January cold blast that I began discussing earlier today.

Teleconnection forecasts from the ESRL agency appear to be handling the upcoming pattern decently well, with a few spots that may be refined in future forecasts. The Pacific North American (PNA) index is projected to be deeply negative in the short term, meaning deep troughing across the West US. I expect we see this deep negative forecast moderate to more neutral territory, as the MJO does not really support such a huge -PNA event. I find it more likely that this strong troughing will be more displaced to the east, as ensemble guidance supports. From then on, we see another negative PNA spell before spiking positive. I have good confidence in that +PNA spike in the long range, with some decent confidence in relatively neutral PNA values in the medium/long range. For the North Atlantic Oscillation (NAO), the index is projected to remain positive throughout the forecast period. I figure we will see a slight negative trend in the long range +NAO values, as an MJO Phase 7 supports more negative NAO values. However, other than that, I feel confident in the prolonged +NAO forecast. The West Pacific Oscillation should stay positive for much of the forecast period before a reduction to neutral or negative territory comes about in the long range in response to the transitioning MJO. I disagree with this WPO forecast. The East Pacific Oscillation (EPO) looks to me like it will be more negative than positive. The medium and long range EPO is projected to be positive, but ensemble guidance disagrees and places the EPO at a more neutral or slightly negative stance. I expect we will see some correction in that direction for future teleconnection forecasts.

To summarize, I anticipate some warmer weather arriving in the wake of brutal cold for the second week of January, before we see a trend towards colder conditions in time for the end of that second week and into the third week of January.

Andrew

Polar Vortex to Unleash Historic Cold Across Plains, Midwest

There are increasing signals that we will see the polar vortex unleash potentially historic levels of cold air upon the nation, mainly targeting the Plains and Midwest.

Kyle MacRitchie

The Madden-Julian Oscillation (MJO) is projected to move into Phase 6 as we progress into January. For those who don't know, the Madden Julian Oscillation involves the placement of enhanced tropical convection over the Equatorial Pacific, extending from the Indian Ocean to roughly the middle of the Pacific Ocean nearly due east of northwest South America. The MJO entering Phase 6 means that the enhanced tropical convection will be northeast of Australia. After that Phase 6 movement, it looks like we will head on in to Phase 7 of the MJO, and that's the one we need to keep an eye on. This forecast, made by four separate CFS ensemble members, shows us entering Phase 7 around January 15th.

MJO Phase 7 500mb Height Anomaly Composite

If we take a look over RaleighWx's Phase 7 500mb anomaly chart, we see that Phase 7 of the MJO in January sees major ridging forming over the Western US and well into Canada, even over the Bering Sea. This is a classic example of a positive Pacific North American (PNA) index, which alters the jet stream so that the jet stream spikes north in the West due to that ridging, and then plummets southward in the Central and East US. This leads to a pattern highly conducive for cold weather in those areas. Adding to that conducive pattern is the highly negative North Atlantic Oscillation (NAO), as is exemplified by the heavy ridging over Greenland. All of this ridging across the upper latitudes then allows a negative Arctic Oscillation (AO) to form, which only adds to the intensity of the cold air in the US. All in all, the Phase 7 really creates the best environment that we can look forward to in the medium/long range for some cold weather.

This is all good and fun, but the really interesting stuff comes up when you take a look at the Climate Prediction Center's analog-produced upper air outlook for the medium range.

Does this chart look familiar? It should, because the anomaly placements are almost identical to the Phase 7 composite above when viewing the North American continent. We see extreme ridging over the Gulf of Alaska, which then allows for the formation of not only a deeply negative EPO (a key player in this impending brutal cold spell), but also a classic McFarland Signature look.

This image from the National Weather Service in 2010 shows what the McFarland Signature looks like. You have the massive ridge set up across the Gulf of Alaska and into the West Coast, and this leads to deep negative height anomalies developing just to the east, usually in the Central and East US. These deep negative height anomalies allow frigid air to be transported from the upper latitudes down into the United States, and I anticipate a very similar situation to evolve here again in the medium range time frame.

Taking a look back at that analog image above the McFarland picture, we see not only the well-established McFarland Signature/-EPO, but those deep negative anomalies being projected as very pronounced across the Central United States. Based on how pronounced those anomalies are, as well as analyzation of the jet stream and temperature patterns during this timeframe, it does appear that the polar vortex would be entering the United States. This wouldn't be any low pressure system; if this were to happen, we're talking record cold. Remember that the polar vortex is the low pressure system that sustains the cold air in the Arctic, so bringing a portion of that vortex down south into the US could be disastrous for farmers growing crops not only across portions of the Central and Eastern US, but also down in the South.

Model guidance is in good agreement about the polar vortex first affecting the United States around January 6-8. Beyond then, we may have to wait a little while until the MJO gets into Phase 7 before we see a resurgence of cold.

ECMWF Temperature valid Tuesday morning.

GFS Temperature valid Tuesday morning.

Andrew

January 1-3 Significant Winter Storm - Part I (Midwest, Great Lakes)

This post will address the first part of the January 1-3 winter storm, where anomalously strong clipper system will lay down significant snows in portions of the Midwest and Great Lakes. You can find the link to Part II, which addresses the effects on the Northeast, at the bottom of this post.

Global model guidance is in agreement with an Alberta Clipper system dropping down from Canada and traversing the Plains to enter the Midwest. Model discrepancies begin to evolve early on, namely when the NAM model takes the snow swath unusually far north into Central Wisconsin. More recent runs of that model have corrected southward back towards Southern Wisconsin and Northern Illinois, but that model will still have to be monitored. GFS/GGEM/ECMWF models hold the consensus with this super-charged clipper, as all three bring about significant snows stretching from Iowa to Chicago back into portions of Indiana and near Ohio.

Global model guidance has been putting down liquid amounts around 0.6" to even 1.0" in northern Illinois into Michigan, and it is those areas highlighted above by the ECMWF that we are monitoring in this post. This event is actually a combination of as many as three different clipper events, with the third one bringing the most snow around New Year's Day. Because they're clippers, right off the bat we are going to most likely see higher snow-to-liquid ratios than usual. A typical snowfall has a 10:1 ratio, which means 10 inches of snow could be melted down into 1 inch of water. In this case, however, we're thinking that places like Chicago could see snow ratios of 15:1 or even 18:1, which means 1 inch of water could theoretically be fluffed up into 18 inches of snow. The ECMWF model above gives downtown Chicago 1" of precipitation, thanks to some additional lake enhancement, and if we were to use a 15:1 ratio throughout the whole event, maybe ending on higher ratios in response to possible lake enhancement, I could envision up to 15-17" of snow. Realistically, that is unlikely to happen. I find the ECMWF to be too bullish (overdone with precipitation) for my liking. The GFS/GGEM seem slightly more in line, with amounts closer to 8-15" being produced. This event would be a significant one if it were to verify as it stands right now. And while I don't trust the 15"+ forecast being implied by the ECMWF, it is theoretically within the realm of possibility.

My thinking for this part of the event is that the areas of southern Wisconsin, northern Illinois, northern Indiana, southern Michigan and northern Ohio will receive heavy snowfall from this system. Based on current model projections, I would issue a call for 10-15" for those areas (with potentially higher isolated amounts), but based on a slight concern models may draw back on QPF projections (quantitative precipitation forecasts, also known as precipitation forecasts), I'll go with a conservative 8-12" for the aforementioned regions, with the very possible chance for higher amounts.

For Part II of the January 1-3 Significant Winter Storm, please click here.

Andrew