March 11-14 Potentially Significant Snowstorm

As I discussed back on February 25th, we're looking at the potential for a significant winter storm in the March 11-14 timeframe, narrowed down from the original March 12-17 timeframe.

The ECMWF model's 500mb vorticity forecast for March 12th is shown above, and we see the two ingredients for our storm on this map. We see the main piece of energy as an elongated swath of positive vorticity stretching from Nevada to Missouri, with our second player dropping south on the lee side (east side) of the ridge stretching across the West Coast. We also see a piece of energy in the Gulf of Mexico which will do its part to interrupt the severe weather aspect of this storm, which is why we'll be focusing on the snowy side.

The ECMWF develops a 997 millibar low centered over southern Illinois on the morning of March 12th, with overpowering high pressure to the north suggesting we aren't likely to see any big northward shifts with this storm in the future. Model verification confirms this idea. As far as the projected storm, this 997mb low is just the elongated system, not accounting for the system dropping from Canada which will eventually phase with the aforementioned system in Missouri.

By the morning of March 13, the system is rapidly deepening in the Mid-Atlantic as the two pieces of energy have begun to phase. This means that they are combining into a single storm system, which only intensifies the snow potential for this event. From March 12th's jet stream forecast, I would expect we see the system try to push east due to a rather zonally-oriented jet stream across the United States, which isn't that favorable for the system to shoot up the coast. However, by the time it hits the coast, the jet stream is essentially laying out the red carpet for the system to go northeast and affect the Northeast.

The snow map for the ECMWF would dump amounts of upwards of 12" across much of the Northeast, including coastal regions, while laying down over 6" in Ohio and a portion of Indiana. This would all depend on phasing of these two systems, which the folks at the National Centers for Environmental Prediction (NCEP) indicate may not be so likely. They indicate that models tend to phase systems too often, when in reality, they don't end up phased. This could be one of those situations, but I guess we'll just have to wait and see.

The GFS model, on the other hand, is much less enthusiastic when compared to its European counterpart. We see both systems shown above, valid for the same timeframe as the 500mb vorticity map we looked over at the top of this post, but in the GFS' case, the layout is different. The GFS model keeps the system back in the Southwest, on a positively-tilted axis, meaning the strongest vorticity values are pointing in a southwest direction. I have a feeling the GFS might not be grasping this system correctly. The NCEP agency also states that models in general have a bias to keep storms in the Southwestern US for too long, when in reality they eject from the Southwest quicker than forecasted. This would work in favor of the ECMWF's solution. However, the GFS does not phase the two systems, which results in noticeably less snow and precipitation in general. We'll need to watch both models for this system in the next few days, as both appear to be hanging on to one bias while letting go of another one. In this case, the ECMWF may be phasing the systems too eagerly but not holding the energy back in the Southwest, while the GFS looks to be keeping the system in the Southwest but not phasing the storms.

Andrew

Major Severe Weather Outbreak Expected in Mid-March

I'm watching out for a potentially significant severe weather outbreak that would occur in the middle of March. Please note that due to the long range nature of this post, it is possible that the event does not happen. What I show below gives you my current thoughts on the situation that are very much subject to potentially drastic change.

(The following is copied from the March 12-16 Potential Storm post) Shown above are ECMWF model projected 500mb height anomalies over the North Pacific, valid on March 6th. We want to take a look at Japan in this image, which is on the left-hand side of this graphic. If we look at Japan, we see deep purples over the island nation, indicating the presence of anomalously low heights. This tells us there is a storm system afoot; the purples indicate the storm is of the stronger variety when compared to other systems. How can weather in Japan relate to weather here in the US? If we use the 6-10 day correlation, explained by Joe Renken, which states that a storm system in Japan can affect the United States 6-10 days later, we find that this storm system would be expected to create a storm in the United States during a March 12-16 time period. 

There is something I'm watching in this time period and on model forecasts. If you were to animate the maps over the North Pacific, you would find that it almost seems like two separate systems impacting Japan over the March 6th time period, but the proximity to one another makes it seem like one big storm. It might take a little while to determine if this really is one strong system or two moderate systems, but until then, it's better to err on the side of caution and discuss how a single, strong storm system could impact us.

We can actually figure out the projected track for this storm as well, by using a tool titled 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, unchanging 40-60 day interval for the next ~10 months before it dissipates over the following summer. Since this season's cycle has been holding at around 57 days, we can go back from the March 12-17 period and arrive around the  January 16-20 time period. The image above shows observed 500mb height anomalies from the January 16-20 timeframe, where North America is located on the upper right portion of the image. If we look at what the atmosphere was like in that mid-January period, we find a defined northwest flow scenario, with strong ridging over the West Coast leading to deep negative height anomalies across the East Coast. The jet stream below for the same January 16-20 period reflects this northwest flow.

(End copied portion) Take a look at the jet stream pattern above. For this period (January 16-20) and the period prior to this (roughly January 11-15), we saw a phased jet stream over the United States. The phased streams are more pronounced in this image, as we see the subtropical jet stream and Pacific jet feeding into a band of stronger winds located over the Gulf of Mexico. Using the LRC, we can predict that not only will this sort of weather pattern come back, but the jet stream pattern should return as well. Additionally, with the jet stream naturally lifting north as we enter the spring season (though it sure doesn't feel like it), the severe weather risks begin to shift more on-land as the stronger jet streams gather more moisture from the Gulf of Mexico. We're already seeing the Pacific jet stream pretty amped up as of today, which looks to play into this potential mid-March severe weather outbreak.

Observed jet stream

Based on the LRC and the rather ominous jet stream pattern observed in Mid-January, my concern is raised for a severe weather event in the middle of March, particularly around March 13-17.

Paul Roundy

Here's where we get into the really concerning stuff. Shown above is a chart of six different types of outgoing long wave radiation (OLR) anomalies. We want to focus on the middle panel of the left-hand side, where it says MJO OLR anomaly on February 16, 2014. On February 16, 2014, we saw negative OLR anomalies just south and east of the subcontinent of India. This location of the -OLR anomalies (which indicate enhanced tropical convection) tells us the Madden-Julian Oscillation was in Phase 2, out of its 8 possible phases. Check out the severe weather event that occurred just four days later, on February 20, 2014.

On February 20, 2014, we saw a large-scale severe weather outbreak, as the chart of storm reports from the Storm Prediction Center shows above. The outbreak was primarily a damaging wind event, as you can see by the large swath of blues across Tennessee and Kentucky, just to name a few of the many affected states. However, we also saw a handful of tornado reports. The fact of the matter is, this severe weather event and the MJO entering Phase 2 are not coincidence. They are correlated with one another. See the AMS (American Meteorological Society) article below:

The Madden–Julian oscillation (MJO) has been linked to weather variability in the midlatitudes via its associated overturning circulations and Rossby wave trains that redistribute the thermal and mass fields at higher latitudes. This work examines the relationship between the MJO and violent tornado outbreaks in the United States. A census of events shows that violent tornado outbreaks during March–April–May (MAM) are more than twice as frequent during phase 2 of the Real-time Multivariate MJO (RMM) index as during other phases or when the MJO was deemed inactive.

If you didn't get what this was saying, don't worry. Basically, it tells us that when the MJO is in Phase 2 during March, April and May, or when we see enhanced convection south and southeast of India, we tend to see the chances of a violent tornado outbreak skyrocket in comparison to the nonactive MJO, or the MJO in other phases. While the February 20th event wasn't exactly a tornado outbreak, it was a severe weather event, and this has me concerned for mid-March.

Let's take a look at the forecasted OLR anomalies for March 12, 2014. Once again, we'll look towards the panel labeled MJO OLR Anomaly. If we look at the forecast by Paul Roundy above, we can see very deep negative OLR anomalies placed just south and southeast of India. These blues are far deeper than what we saw on February 16, meaning that this Phase 2 MJO event could be even stronger, and thus the severe weather event would be even stronger as well. Going by the LRC we discussed above, as well as the AMS document analyzed here, I am concerned that we will see a potentially significant severe weather outbreak for the mid-March period. Because there could be a lag period between the MJO Phase 2 event and the severe weather event of about 4 days, like we saw with the February event, I'll make a tentative timeframe of March 13-18 for a potential severe weather outbreak. This one has me worried, and while you should not be worried yet, it's something to watch out for in the future.

Andrew

March 16-20 Potentially Significant Storm System

I'm watching for a potentially strong storm system in the March 16-20 timeframe.

WeatherBell

The image above shows 500mb height anomalies over the North Pacific, valid on the morning of March 10. If we look at Japan, we see deep purples over the island nation, indicating the presence of anomalously low heights. This tells us there is a storm system afoot; the purples indicate the storm is of the stronger variety when compared to other systems. How can weather in Japan relate to weather here in the US? If we use the 6-10 day correlation, explained by Joe Renken, which states that a storm system in Japan can affect the United States 6-10 days later, we find that this storm system would be expected to create a storm in the United States during a March 16-20 time period. Even more interesting is how models bring two strong storm systems through Japan during this March 10 time period, meaning we could be in for a significantly stormier and cooler than normal mid to late March.

We can actually figure out the projected track for this storm as well, by using a tool titled 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, unchanging 40-60 day interval for the next ~10 months before it dissipates over the following summer. Since this season's cycle has been holding at around 57 days, we can go back from the March 12-17 period and arrive around the  January 16-20 time period. The image above shows observed 500mb height anomalies from the January 16-20 timeframe, where North America is located on the upper right portion of the image. If we look at what the atmosphere was like in that mid-January period, we find a defined northwest flow scenario, with strong ridging over the West Coast leading to deep negative height anomalies across the East Coast. The jet stream below for the same January 16-20 period reflects this northwest flow.

If you're a weather buff, you probably know where I'm going with this. If not, pay close attention. The northwest flow scenario involves the jet stream shooting north into Alaska due to that massive ridge of high pressure, before plummeting south into the Southeast and then north again across the East Coast. In the January 16-20 period, we also saw support from the subtropical jet stream, which helped to enhance wind speeds and phase the two jet streams. If a storm were to come along during this northwest flow scenario, it would most likely become enveloped in the jet stream, and become a coastal storm. To sum up, if the LRC cycles again to be even somewhat close to what we saw in mid-January, it's possible this ends up being an East Coast storm. However, because we're so far out, we don't even know if this storm will even happen. This is just a heads-up for a part of what could be a very stormy mid-March.

Also see: March 12-16 Potentially Significant Storm System

Andrew

March 12-16 Potentially Significant Storm System

I'm eyeing a potentially significant storm system around the March 12-16 timeframe.

Shown above are ECMWF model projected 500mb height anomalies over the North Pacific, valid on March 6th. We want to take a look at Japan in this image, which is on the left-hand side of this graphic. If we look at Japan, we see deep purples over the island nation, indicating the presence of anomalously low heights. This tells us there is a storm system afoot; the purples indicate the storm is of the stronger variety when compared to other systems. How can weather in Japan relate to weather here in the US? If we use the 6-10 day correlation, explained by Joe Renken, which states that a storm system in Japan can affect the United States 6-10 days later, we find that this storm system would be expected to create a storm in the United States during a March 12-16 time period. 

There is something I'm watching in this time period and on model forecasts. If you were to animate the maps over the North Pacific, you would find that it almost seems like two separate systems impacting Japan over the March 6th time period, but the proximity to one another makes it seem like one big storm. It might take a little while to determine if this really is one strong system or two moderate systems, but until then, it's better to err on the side of caution and discuss how a single, strong storm system could impact us.

We can actually figure out the projected track for this storm as well, by using a tool titled 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, unchanging 40-60 day interval for the next ~10 months before it dissipates over the following summer. Since this season's cycle has been holding at around 57 days, we can go back from the March 12-17 period and arrive around the  January 16-20 time period. The image above shows observed 500mb height anomalies from the January 16-20 timeframe, where North America is located on the upper right portion of the image. If we look at what the atmosphere was like in that mid-January period, we find a defined northwest flow scenario, with strong ridging over the West Coast leading to deep negative height anomalies across the East Coast. The jet stream below for the same January 16-20 period reflects this northwest flow.

If you're a weather buff, you probably know where I'm going with this. If not, pay close attention. The northwest flow scenario involves the jet stream shooting north into Alaska due to that massive ridge of high pressure, before plummeting south into the Southeast and then north again across the East Coast. In the January 16-20 period, we also saw support from the subtropical jet stream, which helped to enhance wind speeds and phase the two jet streams. If a storm were to come along during this northwest flow scenario, it would most likely become enveloped in the jet stream, and become a coastal storm. To sum up, if the LRC cycles again to be even somewhat close to what we saw in mid-January, I would anticipate a Nor'easter or some sort of coastal storm for this March 12-16 period. Lots of time for this to play out, but historically, the East Asian correlation and LRC have been doing very well, and I see no reason to discount them now.

It's also worth noting that with this system we could see a rather pronounced severe weather threat. As we enter spring, storm systems can become more 'dynamic', for lack of a better term, and pull up more moisture to enhance the severe weather threat. The jet stream, which naturally strengthens as we enter spring and summer, could only add fuel to this potential severe weather fire. I'll have more on this aspect a little later down the road.

To sum up:

• A storm system will impact Japan in the March 6th period, leading to a storm threat in the US over March 12-16.
• Cold weather is also anticipated during this timeframe.
• Based on two reputable indices, we could be looking at a Nor'easter for this time period.
• If there are two storms instead of one, like we discussed at the top of this post, there could be two coastal storms (but that will need more investigation).
• There could be a severe weather risk with this event.

Andrew

Weekend Snowstorm Targets Midwest, Ohio Valley

I'm expecting a snowstorm to impact the Midwest, Ohio Valley and East Coast this weekend.

As the graphic above shows, I anticipate the heaviest snow to extend from northern Missouri through Illinois, Indiana, Ohio and into Pennsylvania and New Jersey. West Virginia and Virginia will also be impacted by heavy snow. I anticipate we see amounts somewhere in the 6-8" range over the Midwestern states I just mentioned, while areas along the East Coast have a higher upside, possibly near 12". With this storm comes the threat for freezing rain, and I expect this threat to reside from Arkansas into Kentucky, eastward through the Virginias. Pinpointing the location of freezing rain is difficult, and with model guidance still having numerous issues handling this event, do not be surprised if my forecast chances later today. I based this map off of the 12z GFS, seeing as the system has finally made it ashore and a general forecast with this layout appears to be the consensus at this time.

A look at enhanced water vapor imagery shows the storm system making its way onshore, throwing out massive amounts of moisture ahead of it, as the warmer colors show. The circulation of the storm remains just offshore of California, a bit east of that swath of dry air depicted in dark blues. As the system makes its way onshore, we should see model guidance improve and (hopefully) settle on a solution, as the weather balloons sent up by each National Weather Service office at 6 AM and 6 PM (central time) each day will be able to ingest data from the storm, which then feeds into the models to make a more accurate forecast.

There is some talk about model guidance underdoing precipitation in this storm, and also being too far south. The jet stream is predicted to be aligned in such a way that the storm would normally push further north than it is currently projected to go, and we would typically see the heaviest snow shifted to the north as well. However, with models standing their ground on the storm staying south, and both the northern and southern jet streams now "sampled" by those weather balloons, having been onshore for some time, tells me that the storm will most likely stay on its southern track. The under-doing precipitation claim is a bit more difficult to decipher. On one hand, model guidance is notorious for over-doing precipitation when you compare observed precipitation to forecasted precipitation, but in this scenario, we will have a strong jet stream and Gulf of Mexico moisture feeding into the environment, which would usually help enhance precipitation totals. I want to wait for a bit before making a call on that issue, because it'll most likely take a close analysis of radar trends to determine how model guidance has been handling that aspect of the storm.

Andrew