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Saturday, December 3, 2016

Some Light Snow Before Cold Air Dives Down

A weak storm system will bring the first round of accumulating snow for many across the Upper Midwest on Sunday. Generally 1-3" is expected for most areas that see persistent snow. With the more moderate snow coming during the afternoon for many, accumulation on roadways will be minimal south of I-90 as temperatures will be hovering right around freezing. Persistent bands of moderate snow may yield up to 3", maybe 4" of snow on grassy surfaces in southwestern Wisconsin. Total snow forecast by Monday morning below.

Thursday, November 17, 2016

Winter Storm To Kick-Off Winter Season

A developing storm system is emerging from the Rocky Mountains and is poised to move towards the Upper Midwest Friday. The area of low pressure will deepen with time and so will the amount of snow on the northwest side of the track. An area of 5-10" is expected through parts of Minnesota, with isolated locations picking up over a foot of snow. Some lake effect snow is expected in parts of Michigan as the cyclone pulls away from the area. Much of the lift, needed for heavy snow, is thanks to an area of large temperature gradient, see below.


At 700mb, temperatures vary almost 40 degrees across the state of Minnesota,  allowing for avlarge amount of frontogenesis. This process of cold air brushing into warm air creates a large scale rolling motion in the atmosphere and aids in favoring upward motion where we expect the heaviest snow.

We seem to be headed towards a more active winter pattern, with more snow chances next week and beyond. More info always on my twitter account: Link

Tuesday, October 25, 2016

OFFICIAL MIDWEST 2016-2017 WINTER FORECAST

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It's that time of year again, the leaves are changing, the presence of hoodies is on the rise and the burning question on everybody's mind seems to be, "What should we expect this winter?" Long range forecasts are used by businesses to manage risk or manage supply of weather-demand products, and they are becoming increasingly important. Some people live for the snow and cold, and some could do without. No matter what side of the spectrum you fall, you likely have an interest of what to expect this winter. Alright, let us dive into the Midwest Weather Winter Forecast for 2016-2017! Full forecast at the bottom of the page.

2015-2016 Recap:


The story of last winter was the extensive warmth across the entire country. This was, in large part thanks to a strong El Nino in the Central Pacific. A strong El Nino is described as a warming episode in the Equatorial regions of the Pacific. In fact, last year was a top 3, possibly top, warming event since 1950. It had a profound effect on temperatures in the Midwest and last season was no exception. Overall, the warmer temperatures favored below normal snowfall, yet some places were caught under a few storm tracks and saw above normal snowfall. Here is a link to how the forecast panned out last year: The Midwest Weather 2015-2016 Winter Forecast

2016-2017 Discussion:

In most winter forecasts the state of ENSO, or El Nino/La Nina is examined and much of the forecast is based on this index. However, this year we are sitting at a neutral state to eventual weak La Nina and are forced to look elsewhere for more clues. Contrary to last year, a lot of the weight was given to the El Nino, this will not exactly be the case this time around. Putting too much emphasis on the projected weak La Nina may prove to be a flaw in other published winter forecasts. We will examine the state of other regions in the Pacific and Atlantic Ocean to help create analog years, or years with similar conditions to use as a proxy for the 2016-2017 season. This process has been proven successful in the past several years for Midwest Weather. And because every year is different, we will look to pick out the major differences and potential factors that will have the largest impact on the upcoming winter. 

ENSO:


The state of ENSO has been hovering around -0.5 since the summer and most models continue to hold steady at this rate. It implies a neutral to weak La Nina, or slightly below normal ocean temperatures in the Central Pacific Ocean. Usually in the transition to a La Nina, up-welling will occur in the eastern Pacific, bringing colder water to the surface. This cooling process has yet to establish itself as the water temperatures in the mid to upper level of the ocean have stayed warm. Confidence is high that we will not turn to a moderate La Nina anytime soon. For our case, we will examine years in which the ENSO index was within 0.0 to -1.0. Below are the top 20 winters that best resemble a 0.5 ENSO value for December through February; their results on temperature are plotted below: 


Pacific Decadal Oscillation (PDO):

The Pacific Decadal Oscillation (PDO) is a pattern of Pacific climate variability similar to ENSO in character, but which varies over a much longer time scale. The PDO can remain in the same phase for 20 to 30 years, while ENSO cycles typically only last 6 to 18 months. The PDO, like ENSO, consists of a warm and cool phase which alters upper level atmospheric winds. Currently we are in the positive phase of the pattern and should last through the winter, its effect on the overall weather pattern is a major factor.


The positive phase of the PDO is described as warmer than average water in the Gulf of Alaska down through the Pacific Coast of the United States. The subsequent result of this warm water is a cold blob of water further off to the south and west, by virtue of ocean currents and areas of up-welling. The plot from Unisys shows the SST anomalies resembles these exact conditions. 

The figure below shows how positive PDO winter have influenced temperature anomalies over the period from 1951-2010. 


A bit contradictory to the state of ENSO right? This is why we will continue to examine other factors around the globe for the sake of our winter forecast.

Atlantic Multi-Decadal Oscillation (AMO):

The Atlantic Multi-decadal Oscillation (AMO) is a mode of natural variability occurring in the North Atlantic Ocean and which has its principle expression in the sea surface temperature (SST) field. The AMO is identified as a pattern of variability in North Atlantic SSTs. We are in the positive phase of the AMO as well. However, we may be making a turn towards the negative phase. The SST anomalies plot from Unisys plot above also shows some pooling of colder water, which is part is due to sea ice melt adding fresh water to the ocean , locally changing the water density is some spots. Given these factors and since the Atlantic is downstream to the United States, the AMO will  be less of a factor on the winter forecast than it has in other years. The winters closely related to the positive phase of the AMO:


Quasi-Biennial Oscillation (QBO):

The quasi-biennial oscillation (QBO) is an oscillation of the equatorial zonal wind between easterlies and westerlies in the tropical stratosphere with a mean period of 28 to 29 months. The alternating wind develops at the top of the lower stratosphere and propagates downwards at about 1 km (0.6 mi) per month until they are dissipated at the tropical tropopause. This wind pattern has an influence on the weather patterns in North America. Coincidentally, we are also in the positive phase of the QBO as well. The winters that best resemble the current state of the QBO are averaged below:


Siberian Snow Cover:

Dr. Judah L. Cohen has done research on the state of the snow pack in Siberia (His research). He has shown a correlation in snow cover to the level of cold air intrusion to North America. When October snow cover is above average, cold air has a better chance of manifesting itself into the Midwest. Below are the top closest years that best resemble the current state of snow cover across Eurasia: 


Putting it all Together: The Best Analogs

Clearly each factor in the forecast gives a different result on temperatures and the subsequent winter forecast. A way to resolve this is to use analog years, using winters that best take into account each factor. The process was to first find years that best held these conditions:

ENSO: 0 to -1 | PDO: Pos (+) | AMO: Pos (+) | QBO: Pos (+) | Sib Snow: Above Ave


Below are the best analogs based on all factors and are given weights that best describes how related each year is to the upcoming winter:


Here is the result on temperature for December through February:


And the result on precipitation: 


And the result on geopotential height at 500mb and surface pressure:


The analogs suggest the midwest is at an increased chance for below normal temperatures, near to possibly above average snow and an increased risk for large winter storms. Yet every year is different, so let's continue...

A Look at the Models:


Models are starting to trend towards a cooler solution for the winter, which coincides with our analogs, but still suggest some spots could still be at or slightly above average. The CFS model, which is a low resolution model that run 4 times a day out to a year, also has an increased chance for slightly above normal precipitation in parts of the Midwest.

State of the Arctic Ocean:


A more organic method in forecasting is to directly look at the current conditions. For a North American winter, the Arctic Ocean plays a major role in how cold the winter can get, and it's actually counter intuitive. 

The extent of Arctic sea touched a record low this week. Furthermore, the ocean water temperatures are well above average and approaching records as well. These two factors have implications on the polar vortex, yes the polar vortex. The strength/magnitude of the vortex, or jet stream around the Arctic Circle depends the temperature gradient, which is the change in temperature from the north pole to areas further south. The colder the North Pole is, the largest the temperature gradient and the stronger the polar jet gets. A warmer north pole leads to a weaker polar vortex by the opposite logic. Consequently,  strong polar vortex spins fast and locks in the colder air for areas further north, while a weak polar vortex spins slower with more wobbles, allowing colder air to reach areas further south, including the Midwest. Think of it as a top spinning, as it slows there is more wobbles, just like the polar vortex. Each one of these wobbles has the potential to bring colder air to the mid-latitudes. In summary, conditions favor better chances for more shots of cold air into the United States than prior years. And it's all thanks to warm Arctic Ocean temperatures! Isn't weather strange sometimes? Here is a look at sea surface temperature departures from average:



THE OFFICIAL 2016-2017 WINTER FORECAST:

Overall, the forecast suggests a much cooler winter than last year with the potential of more snow for many. Expect several cold spells, yet each arctic blast is not expected to last long. There should be more variability in temperatures from week to week than average, setting up a higher potential for large winter storms to develop. Warm waters (5-6 degrees above average) will prolong and enhance the lake effect snow season. There will also be an increase in Alberta Clipper-like systems that drop a quick 1-3"/2-4" snowfall during cooler periods this winter. Spring may come earlier than usual, even with cooler temperatures through the winter. While only Mother Nature will have the final say, it looks to be a good 'ol fashion winter for the Midwest.

Bachelors in Atmospheric & Oceanic Science
University of Wisconsin-Madison

Thank you for reading. You can find more by following on Twitter and on Facebook.

Here is the final forecast:




**Be sure to keep it here to Midwest Weather for updates throughout the winter!

References:

- National Center for Atmospheric Research
- Earth System Research Laboratory
- Zack Labe for his arctic sea ice plot
- Tropical Tidbits for CFS plots
- Midwest Regional Climate Center
- Unysis 
- Climate Prediction Center

Tuesday, September 13, 2016

2016-2017 Midwest Winter Forecast Details

Our official winter forecast will be released in Mid-Late October. Current and initial indications suggest/favor a cooler than average and possibly more snowy than average winter. Certainly it will be colder than last winter, in large part due to a record breaking El Nino in the Pacific Ocean. More research and forecasting will need to be done in the next several weeks, be sure to check back here and on social media (Facebook & Twitter) for more as we gear up for another winter season. Thanks for visiting.

Monday, April 25, 2016

SPC Outlooks, Survey Results and Discussion

Recent advancements in numerical weather prediction and an increasing degree of the science behind severe weather has been great for meteorologists. However, does this newly found knowledge translate into a better public outreach and public preparedness? Stakeholders with direct communication to meteorologists would say yes, but this does not necessary translate down to the average citizen. While severe weather research and increases in computing power seem to be the new space race within the weather community, the social science aspect is apparently lagging behind. Yes, the National Weather Service has been committed to understanding the general public's needs, for several years. Even in 2012 funding was allocated to the cause. However, we are not quite there for the best understanding of severe weather forecasts within the public.

Most of the confusion comes with the wording with in the Storm Prediction Center. While it is hands down the best severe weather forecasting center in the world, recent changes to their 0-3 day outlooks have been problematic.. The system is to rank severe weather risk in categories from low to high or, "marginal" to "slight" to "enhanced" to "moderate" to "high." While the system is rather new, the issue comes with consistency, sometimes even within the weather service. For example, the graphic attached is a severe weather forecast from NWS-Mobile. While the graphics is great on its own, what does "elevated" and "significant" actually mean? Does elevated mean enhanced? or?
Not only do you have conflicting forecasts within the weather service, local TV stations can sometimes be a problem as well. The image from CBS-Dallas put out an outlook with percentages, and then an area of "chance of significant severe weather" that does no coincide with the filled in areas. Is this just to include the highest population area, including the Dallas metro? Sure seems that way.. and then you have KFOR in OKC doing their own thing:


Not to mention some of the other weather blog or social media pages out their who are mapping out even more misleading information. In an ideal world every media outlet would use the same format, and things would be consistent. Maybe even a 1-5 scale? Like Europe does, even within their severe weather warnings. It is certainly a known issue within the weather enterprise, but it is what we have...for now.

Let's take a look at some survey results, on the current wording in the Storm Prediction Center's outlooks. 100 people, without a weather background were surveyed.

Asking the participants to rank SPC wording into a 5 point scale, with one being the lowest risk for severe weather and five being the highest risk brought on an average response of:


Notice how the enhanced risk is actually thought to be higher than a moderate risk in the survey. I mean, it's definition is "intensify, increase, or further improve the quality, value, or extent of." In fact 16% of participants put "enhanced" above "high". Slight and marginal risk came back as similar results, yet 90% of the results ranked either of these two as 1 or 2 on the 1-5 point scale. Much of the confusion comes with the term "enhanced." Could a "enhanced-slight" solve this? Maybe? In general it seems people to understand a normal low medium high distribution, as the high risk was closest to its ideal rank of a 5, coming in at an average of 4.38 and 70% ranking it as the highest risk of severe weather. Another solution could be to proceed the outlook with a numeric value of 1-5, or "2-slight risk of severe weather." 

The survey we conducted then went on to ask about what your preparedness based on a forecast. The questions were "If you heard your area has a enhanced/moderate/high risk of severe weather today, how would your day change?" The results are below.



It is good to see that a high risk will tend to lead to more preparedness through the day of the event, while enhanced still seems to cause more stir than a moderate risk. Interesting.

Meanwhile, some good news to report from the survey. People are generally well aware of the meaning between a tornado watch and a warning. Here are some results:




And for good measure, the question of where the participants weather alerts generally come from:



Finally, a couple selected comments from the survey:

- "What's enhanced risk? Never heard of this before"
- "My only concern is regarding the many levels of weather conditions. IE marginal, enhanced and slight all sound the same to me. Why not have more simplified categories such as low, moderate and high?"

Overall, I am not calling for a call to action, but rather conveying the point that, the general public will not understand the caliber of a local map that says, "moderate" risk. Meteorologists need to express the extent of the severe weather threat, maybe by expressing how rare an outlook is.

Thanks for checking out these survey results and brief article. You can always follow me on Twitter or 'like' the Midwest Weather Facebook Page.




Tuesday, March 22, 2016

Major Spring, Winter Storm to Blanket the Midwest

Almost 5 years to the date (Link), another major late March winter storm is poised to strike the Midwest with heavy snow and severe weather to the south. Moderate snow will break out in the northern Plain on Wednesday morning and spread northeast through the day on Wednesday into the early morning hours of Thursday. Computer models continue to bounce around a tad with the exact track of the axis of heaviest snow, but the map on the left is the best bet of where the 6"+ area will set up. Areas closer to the warm front will see some mixing at times of a heavy wet snow, which will limit snow totals as it melts and compacts through the day and even through the overnight on Thursday. Models have been consistent in placing the heaviest band of snow from far SE MN through an area just north of Green Bay, Wisconsin. Confidence is high in this location, but on the outskirts of the band such as Minneapolis a sharp snow to no snow gradient will set up, so more tweaks may be needed in this area, same goes for Madison and SE Wisconsin as the rain to snow line may change 20-30 miles, which would have a profound effect on the total you see on your doorstep. Thanks for stopping by, and feel free to follow on Twitter for continued updates.

Monday, March 21, 2016

Robust Winter Storm Pegged to Strike the Midwest

A wide area of heavy snow is expected to move into the Midwest by the middle half of the week. With an arctic area of high pressure setting up to the north before this event, ample cold air will be set in place, providing support for accumulating snow. Snow is expected to break out in the northern Plains Wednesday morning and trek east throughout the day on Wednesday into Thursday. Being a Spring storm we would expect a wet and heavy snow, and this will be the case with this winter storm as well. Regarding the amount of snow in your area...as always it will come down to the exact track of the low pressure system. There is heavy model support for a track that takes it through southern Iowa to near Chicago into Lower Michigan. This is our favored track, however, one of the more reliable computer models with a good track record is favoring a track further south, dropping heavy snow into areas of southern Wisconsin, and the outlined area in yellow. The trend this winter with the models is to bring the snow further north that originally thought, so the current forecast we are going with is to drop snow, depicted in the areas on the attached snow map, southern Minnesota and central Wisconsin. Lots to work through in the next 12-24 hours, expect a more detailed and pinned down snow forecast by that point. Either way, someone will see a memorable snow event of of this. Follow on twitter for live updates

Saturday, March 19, 2016

Winter to Silence the Doubters, it's not over quite yet.

A fierce winter storm looks to bring a variety of weather to midwest on Wednesday. Usually these systems in late March are tough to pin down the potential and location of heavy snow, but with ample cold air settling in, it looks to be a classic looking mid-winter snow event. Weather computer models have been coming together through the last couple days of a track through Nebraska to near Chicago and points east. This would lay down a swath of moderate to heavy snow on the northwest side of the track, with thunderstorms further south and west. In all honesty, this system has been very consistent in the latest model runs and atmospheric data, compared to other systems. However, being that it is still 4-5 days out, amounts and exact locations are certainly in question, but the idea of heavy snow is of high confidence, somewhere across the Midwest. Most likely area in question within the blue shading. While this may change, a broad area of 6-10" of snow if possible, depending on whether or not your area sees the bulk of the snow during the day or during the night. Either way, much of it should melt quickly with a higher sun angle this time of year. There are a couple more systems that may threaten the Midwest further down the pipeline as well. Be sure to check back for updates, as the event nears.