MJO Hinting at Active Beginning, End of February

Preword: The Long Range Lookout issued a few days ago is void. This is a replacement post.

The first part and last part of February should be the final pushes for winter, while the middle of February appears to be lost.

The last 40 days has brought the Madden-Julian Oscillation to Phase 8, the phase most commonly associated with winter snow and cold. We have indeed been seeing pushes for cold and snow into the States, most recently with a snowfall event that hit areas across the Midwest, helping their snow drought. Medium range forecasts indicate a continuation of these snowfall threats, with an additional several inches possible across portions of the Midwest and especially the lakeside areas of the Great Lakes.

Long range forecasts portray a Rex Block setting up across the West Coast, with high pressure squeezing into the Pacific Northwest and low pressure residing in the Southwest. The European forecast for this event is on the left, and the American's forecast on the right. The European model predicts high pressure developing across the East US in response to this Rex Block. I do not feel that is the likely scenario; Rex Blocks are more known for producing a more zonally-oriented flow east of the block. I prefer to side with the American model on this one. Low pressure persisting in the Bering Sea is indicative of a positive WPO pattern, something that does favor the European model over the American with warmer temperatures spread across the nation in a positive WPO regime. However, the Rex Block should affect the synoptic US more than the positive WPO, although periodic ridges and warm-ups are definitely within the spectrum of reality. That persistant low pressure anomaly in the Southwest will provide a base for storm threats across the nation, but with my predicted lack of high latitude blocking across Greenland, these storms should take more of an inland path, rather than one going up the East Coast. The long range is more supportive of a solid blocking pattern, but I would rather stick to the more inland tracks for now. These inland tracks may not support snowstorms as a byproduct of the Rex Block (and its zonal flow) is a warmer air mass overall.

Looking ahead into the very long range, into late February, we see that the second image in the first column is predicting strong negative OLR anomalies in the last week or two of February. Negative OLR anomalies are most commonly associated with enhanced convection, and this leads to the predicted Phase 1-2 stages of the Madden-Julian Oscillation. Do not think that this Phase 1-2 regime will continue through mid-February- this would be a sudden rebound event from less favorable conditions in the MJO.

A constructed analog forecast of the OLR anomalies in late February enhances the forecast of the early MJO phases in the late month. One can see the deep blues across the Indian Ocean east into extreme western Pacific waters. These deep blues once again exhibit negative OLR anomalies, and they would be placed in a location suitable for borderline Phase 1- Phase 3. These three phases do support low pressure along the East Coast, but also high pressure in the Rockies that could spill over into the Central US. 

A third long range OLR and 850mb wind forecast from the Roundy MJO page (the above 3 images are from that same page) once again confirms suspicions of deep tropical convection in late February in the bottom-most image. The arrows depicting 850mb wind motions reveal strong westerly winds centered over the Indian Ocean, something that does support tropical convection formation and sustainability. Some models that project the Madden-Julian Oscillation have been hinting at a circling pattern occurring within Phases 8-1 in coming days. While this could indeed happen as exhibited by the analog forecasts and the image just above, I'm not that open to speculating on it, as it is multiple models versus the European suite, something I don't have the confidence to inspect and choose my favored solution.

On a related note, the MJO in Phases 1 and 2 does not favor blocking in the higher latitudes of Greenland, for those of you wondering why I support more inland tracks.

A strong Kelvin wave is currently moving east across the Equatorial Pacific. This Kelvin Wave will result in enhanced warm water anomalies across the ENSO area, which can lend itself to cooler weather in the nation as February progresses. This event will be analyzed more in coming days.

I'm hard pressed to rule out the end of February as a stormy time period, but I'm also hesitant on cold weather for those same dates. It is very apparent we will see chances for snow (likely accumulating in a few cases) as the month drags on, but as the sun begins to strengthen as winter begins to end, it's very possible some systems may just not be able to hold onto the cold air long enough to allow snow to fall. This concern will be addressed in coming days.

Andrew

Revised 2013 Severe Weather Season Outlook

This severe weather outlook has been revised for details and a reconstructed forecast using the best methods I am able to confidently use. The following information is put forth in the utmost confidence with recognition that this forecast does indeed have potential to make some disappoints for verification.

"Severe Weather Hotspot Eyes Midwest, East Plains This Spring"

Hello everyone, I am here to bring you the detailed forecast for this severe weather season. We'll get right on it with my analogues.

We start with geopotential heights at the 500 millibar level for years that had a La Nina early in the preceding year turning into a neutral or slight El Nino winter, again in the preceding year. Also included were years following solid negative Pacific Decadal Oscillation (PDO) years. Looking at the geopotential height anomalies for these analogue years, we find a gigantic swath of below normal height anomalies across the entire West US, including the West Coast and Rockies. The Upper Midwest is also included. More significant than this is the presence of that light green color in the Southeast. This is known in the weather world as the 'Southeast Ridge'. The Southeast Ridge is literally a ridge of high pressure that forms in the Southeast and provokes storms to stay further north in the southern Midwest rather than going through the Gulf Coast. Seeing this in place enhances my initial thoughts that storms will indeed take this track that sends storms (and severe weather) up into the Midwest and Plains.

This analogue image involves the same years as were used in the first image, and for the same spring months. This time, however, the image displays zonal wind anomalies. Zonal wind anomalies just means wind anomalies from west to east. These zonal wind anomalies are valid for the 300 millibar level, which is where the jet stream lies. For those unfamiliar with the upper wind dynamics, when you have the jet stream over you, severe weather potentials are enhanced. However, there is a very special incident that happens when the two main jet streams cross. You see, there are actually two separate jet streams- the Pacific Jet Stream is the one that determines how far south cold weather goes, and directs storms that come from the Pacific. The second jet stream is the subtropical jet stream, and this is the one that really gets the Gulf moisture flowing and pumps up severe weather in the South US. These two jet streams can actually merge into a single, very powerful jet stream in response to a strong storm system. To show just how powerful these merges can be, some of the worst severe weather outbreaks have happened in the midst of merged jet streams. Now imagine if these jet streams merged multiple times during the spring, and you can guess what that means. I pointed out both streams in the above image, but then circled an area of very high wind anomalies in the Midwest and Northeast. Inside this circle is where the jet streams have merged, and thus where I would expect the highest instances of strong to severe weather. Not necessarily the most tornadoes, but a general higher chance of more severe weather events.

Another item to closely watch is the sea surface temperature anomalies in the Gulf of Mexico. As we all know, an important item in all severe weather situations is ample Gulf moisture. Naturally, in above normal water temperatures, moisture is increased as air is inspired more frequently to rise in the face of warmer than normal waters. In a similar aspect, with above normal moisture in the Gulf, storm systems will then drag more moisture north onto land, that then aids in providing instability for severe weather. What this higher moisture also does is enhance heavy rain potentials, as higher moisture saturates the air, thus allowing more rain to fall in weather systems. 

Finally, we have to address the ongoing severe drought that is hitting much of the country. The ongoing drought does exactly the opposite to the effects the additional Gulf moisture has. The drought makes the land so dry that evaporation cannot occur. Thus, when storm systems enter the region highlighted in reds and maroon colors, they will not be able to grab moisture from the ground and cannot produce as strong of storms as would have been produced if the drought was not in place. Also, the drought creates warmer than normal weather over the Plains. Because little evaporation is occurring, clouds struggle to form. This lack of cloud cover enables the sun to shine on in a vicious cycle that supports long-term droughts. The warmer than normal temperatures can then create something called a baroclinic zone, which just means a temperature gradient. That is, the warmer, drier air can create its own air mass that can collide with the more temperate air mass out east. When storm systems plow through, it would not be uncommon to see these conflicting temperature masses enhance severe weather potentials.

I anticipate the best risk of severe weather to be over the Southern Plains, Midwest and Great Lakes. This comes as a result of my analogue years predicting strong merging of the jet streams over this region, as well as the presence of the infamous Southeast Ridge. I did mark the Southeast Ridge with an H in its respective region. Now, if you're wondering how often these outbreaks could be and how often we could have them, that's a whole other story. There will certainly be a period of a few weeks where some strong storm systems could very well bring about some solid severe weather outbreak potentials, but that's all that is known at the moment.

Andrew

Christmas Day Severe Weather Outbreak Could Repeat on Valentine's Day

The atmosphere could very well shape up into a situation that mimics the set-up that occurred on Christmas Day, 2012. The 500 millibar map from that day is shown above. We can see the storm system pushing down well into the Southern Plains, as depicted by the word 'Low' on the map. The national atmospheric flow appears not too disturbed in the East, with the exception of a weak ridge of high pressure in the Southeast. Stronger high pressure stands its ground on the West Coast, and this is the factor that typically allows storms to move east-northeast to affect the Midwest and Plains. The Southeast ridge also supports this.

We all know how that day turned out. Many Christmas celebrations were interrupted by wailing tornado sirens as a tornado outbreak hit. It started in Houston, and ended the day in far eastern Alabama. Along the way, 175 severe weather reports were submitted to the Storm Prediction Center, 60 of which were tornado reports.

I find it plausible that such a situation could indeed happen again, on Valentine's Day. The Lezak Recurring Cycle, which is a repeating weather pattern that occurs through the fall into spring, has a repetition length, or cycle length, of 53 days. This means that 53 days in the future from Christmas is when this atmospheric set-up could come back. And when we tally up the dates, we find that the 53 day mark lines up with Valentine's Day. Not a good thing to see.

I will publish more on this developing situation, and will always let you in on the latest in breaking weather, especially with this system.

Andrew

February 10-12 Potential Winter Storm

There does appear to be potential for a winter storm from the 10th of February to the 12th. Let's dive right in.

Model guidance is in fair agreement that a strong low pressure system will move into the Southwest US ahead of a massive high pressure system in the northeast Pacific, just off the West Coast of the US. This storm system will drop further south into northern Baja California in the days after this forecast image, which is valid for the evening of February 8th. The different shades of colors show confidence levels of the NCEP Ensembles as shown on the blue numbers on the legend at the bottom of the image. You can see that the center of this low pressure system has deep oranges, which correlates to 54% probability of the system ending up there- a fair chance this far out. Notice that there is a very zonal pattern across the central and east US. These zonal wind flows (zonal means west-to-east wind flow) typically result in relatively dry and warm weather across much of the nation. I can already see that this type of pattern could result in a very similar set-up as we enter this storm potential period. If you look back towards the West Coast, you will see that storm system pressing down on the pressure contours, as well as another area in the Pacific pushing up on the pressure contours. These are opposing low and high pressure centers, respectively. If we see the low pressure system drop further south and that high pressure system try to bleed east into the Pacific Northwest, it is very plausible we could see the infamous Rex Block formation emerge.

As illustrated in the above image (made by theweatherprediction.com), the Rex Block involves high pressure and low pressure essentially sitting on top of each other. This can happen anywhere, but for all intents and purposes, it has been shown on the West Coast. If you look downstream towards the central and east US, we again see that zonal flow pattern emerging in the East as a result of this Rex Block.

This is the latest European model forecast for the 11th of February. We can see our winter storm is actually in the Plains and shown as the tight gradient of pressure contours just south of the green-ish color in the region. This comes as a result of not the Rex Block (which is present in this image), but an amazingly-strong high pressure system in the Southeast. While many areas would see rain changing to snow in this event, should this storm even happen, the Southeast Ridge could really get in the way.

To be honest, I don't see this Southeast ridge happening. The only way we could see it would be in an extreme negative Pacific-North American index phase. When that index is negative, low pressure dominates the West Coast, and high pressure forms in the Southeast as a result. However, a glance at this and the previous run of the European model shows actually a positive PNA, which supports storm systems hitting the Midwest and Ohio Valley, rather than the Northern Plains. So I do not support the European model at the moment.

The American GFS model has been showing a pretty consistent solution of having a storm system moving out of the Front Range before sliding northeast and impacting the Upper Midwest, portions of the Central and Northern Plains as well as the Great Lakes. While this is nowhere near as extreme as the European model, this American model still does have a Southeast Ridge, although it is weaker than the European's. This is indeed a much more plausible solution in my opinion, with no unreasonably-strong ridge of high pressure in the East, when the atmospheric pattern does not support it.

I will continue updating this situation as the date draws closer.

Andrew

Long Range Lookout: Winter Slipping Away

Preword: Recently, I have been caught up in the swing of the stratosphere and investing all of my confidence in just a few factors. Starting today, I will present the good and bad sides of the forecasted weather, even though you may not find it as exciting as my other posts.

In a disastrous recurrence of last winter, the winter of 2012-2013 has so far brought little snow and only modestly increased cold in comparison to last winter. Don't get me wrong, this winter has had many more advantages than last, but still remains dismal. The long range will be a classic, painstaking case of some factors looking good while other factors ruin the party. We start with the current 500 millibar anomalies over the Northern Hemisphere. Blues indicate low pressure areas and reds show high pressure regions. Deeper shades of each color indicate stronger modes of their respective pressure systems. We can see a deep blue positioned over the Great Lakes in the wake of a very powerful storm system that impacted much of the nation's population. This area of cold will move on out of the region later on as we head towards the weekend. I want to turn your attention to eastern Asia in the upper right-hand corner of the image. See that massive high pressure system there? That will provoke high pressure in the United States as we enter next week and into the following weekend, and we could see another bout of above normal temperatures. Snow cover that was received in the past couple of days could be eradicated. This comes at a time when high pressure finally emerges into the West Coast, a good sign for cold and snow in the Midwest and East US. But, as a result of the forecasted high pressure system, it will be Alberta clippers that bring the best chances for snow.

We now move ahead to Mid-February. There is no longer high pressure over East Asia, but persistant low pressure anomalies. These low pressure anomalies would then inspire a stormy period to round out the month of February. Could these storms hit the Northeast? I'll discuss that a bit later down this article. Something that certainly is not good is that persistant low pressure in the Bering Sea. This goes with my 'some good, some bad' forecast, as this persistant low pressure in the Bering Sea can lead to above normal temperatures in south-central Canada and much of the northern United States. Even more depressing is the lack of Greenland blocking. Greenland blocking is the phrase that is used to reference persistant high pressure over Greenland. When that set-up happens, the atmospheric pattern is more inclined to introduce more wintry weather into parts of the US. A lack of this blocking leads to a more zonal, west-to-east jet stream that allows for warm temperatures and not many storms. It is very possible some of that high latitude blocking in eastern Europe (shown in deep reds) could migrate over to Europe, but that remains to be seen. Frankly, I'm not that optimistic on the idea. This dismal explanation is verified by slight high pressure in the New England area, likely as a byproduct of the low pressure in the Bering Sea, and in response to a lack of Greenland Blocking. One bit of good news is the forecasted high pressure over the Pacific Northwest. If you get high pressure in that area, the jet stream can be persuaded to dip south and let out some cold into the Northern US. Storms tend to follow a jet stream that favors wintry weather for those same regions, the Midwest and Ohio Valley for example.

Lastly, looking ahead to the heart of February just a few days after the above image, we find that the atmosphere has changed. That high pressure that was in the Pacific Northwest has now migrated into the Gulf of Alaska. This situation can then go one of two ways. The first option is for high pressure to then spread back on land into the Pacific Northwest, or the high pressure pushes west into the Bering Sea. Both moves would support a cooler pattern in the North US, but I'm not betting on it at the moment, as the consensus is not overwhelming and we are over 2 weeks away from this forecast image. We still see persistant low pressure in East Asia, adding to my theory of a stormy end to February. Also, we then see the forecast emerging for some spotty patches of high pressure in and around Greenland. Such an action could provoke a better pattern for the Northeast (notice the high pressure in New England is gone), but it's too far out for me to think about accepting or rejecting this idea.

So we could see some storms in late February, but the big story will be warmth in mid-February, with Alberta Clippers dominating that scene. Early February will be when the effects from the sudden stratospheric warming dies off, so that will add to the troubles the cold may face in the coming month.

Andrew