Meteorological winter started December 1st and we have seen some cold and some warm. I expect to see more topsy turvy weather flips like this to reoccur. Without further ado, the 2022-23 Winter outlook! I am including a quick summary if you don't want to read the entire blog post Quick Summary
December We have started the month cool and it looks like we will stay that way with short warm periods mixed in mainly early on. Look for warmth returning late this weekend and early next week, before being pushed out by colder temperatures midmonth. There is potential for some storm systems (like between the 10th-14th), but it is WAY too early to say whether they will produce sizeable impacts or not. The big question I'm sure some may ask is what the chances for a white Christmas are. At this time, I would say we have an average chance, but that can of course change. January Models have flip flopped on January temperatures, but I am more in line for a warmer solution. Based on the CFS weeklies for late October we will end 2022 cold before heading into a January thaw. Don't be fooled by the warmth, it will still most definitely be winter still. While the month msay be warmer overall we can still stee shots of average to cooler than average air midmonth. With the warmer temps with cooler than average temps just to our northwest we could see a battleground of airmasses set up in the Midwest. This would make me concerned for the threat of ice/freezing rain and wintertime severe weather. It will all depend on where the polar jet stream sets up shop. February Once you get to the end of January and enter February you only have 30 days until meteorological spring, so you're almost there with warmer temps on the horizon. But reconsider that idea. For the last couple years February has seen some of our coldest temps and biggest snowfalls. We saw over a foot of snow from one storm alone in early February this year. I don’t expect that to change especially with our rare third year La Nina which favors a back loaded winter. March March is still a long ways away, but I will touch on some early thoughts. Right now March looks wet and war, but that could easily change. If we go warm I can see increased chances for severe weather. If February's cold sticks around we could see more snow. Yes, March can see snow especially if there is a snowpack in place from February. Final thoughts
There are risks with making any kind of seasonal or sub seasonal outlook/forecast. As I went over in the last blog post there are so many moving variables you need to work with and adjust for. During warm periods like January we can still see cold air and vice versa for cold periods. Another risk is whether a southeast ridge ridge sets up. If that happens, that would be a warmer risk to the forecast. Another is the speed of the change in the teleconnections and could affect timing of pattern changes though I believe the pattern above will be the main one. It's too early to say exactly how much snow we get on average this winter. When and where really depends on storm track and placement of cold air. I think I may write another post later talking about potential types of winter storms we can see later
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I hope everyone had a great restful Thanksgiving and a stomach full of Turkey. On Thursday, our high temperature was 59 deg while our average high is normally 48 deg. While we were over 10 deg warmer than average we were still cooler than our record high of 70 deg set in 1927. Temperature wise the month of November has been close to average with the notable cooldown mid-month. With the exception of parts of the snow belt we have been dry just getting 25-75% of our normal precipitation amount. Before I get into my thought on the upcoming winter, let's talk about the next week or two. Both the American and European ensemble models agree we will start on a warm note. Cold should return around the 5th/6th based on several teleconnections going into cooler phases around that time such as the NAO going quite negative. Actually there is modeling showing a *potential* snowstorm to our north around the 7th. I promise our time for that will come. The BasicsBefore I go into the outlook, I would like to explain what I llok for in making one.
Sea Surface Temperatures and ENSO The largest driver probably would be SSTs and ENSO which influence the teleconnections and jet streams. Take a look at the Bering Sea, the Central Pacific, and south of Greenland. These areasd are important to llok at with teleconnections. Warmer anomalies suggest rising motion and cool anomalies suggest sinking motion in the atmosphere and hence troughs and ridges. ENSO or the El Nino Southern Oscillation is basically the shifting of trade winds in the central Pacific Ocean basicly either allows cooler water to upwell off the peruvian coast or not. ENSO has a cool phase (La Nina), a warm phase (El Nino), and a neutral phase. The large basin wide cool water anomalies show a classic La Nina. Looking at the seven day changes there is some warming of the central pacific basin. The Climate Prediction Center is forecasting a weakening LA Nina and neutral to El Nino conditions by next winter. Regardless, it looks like a triple dip La Nina winter. Teleconnections In short, teleconnections are atmospheric anomalies affecting the weather pattern of a distant area. Some of these teleconnections I look at would be the North Atlantic Oscillation (NAO), Arctic Oscillation (AO), Eastern Pacific Oscillation (EPO), Pacific-North American Teleconnection Pattern (PNA), and Madden-Julian Oscillation (MJO). A teleconnection gives a general idea of the atmospheric patter which can lead to cold, snowy weather vs calm and mild. Teleconnections are more short-term influences, but they influence the wider pattern of the jet stream. You can have either a meridional or zonal flow. A zonal flow if kind of flat allowing for calm weather, while a meridional flow features kinks in the jet stream allowing more extremes to occur. You can imagine the jet stream as having waves so think if you have a ridge on the west coast, there will likely be a trough downstream in the central and eastern US. Likewise with a ridge south of Greenland. The perfect combination for cold in the eastern US would be a -AO, -NAO, -EPO, And +PNA. If you have all agreeing on cold, but one suggests warmth they will destructively interfere with each other. In my experience it is getting a ridge on the west coast (a +PNA) to develop at the same time the rest are negative. Soil Moisture Soil moisture isn't as important right now, but more for next spring. Lots of moisture in the soil can be evaporated and substain storm systems when they pass through. If the soil is dry there won’t be as much moisture to work with unless the system can tap into more tropical moisture from the Gulf of Mexico. To get a lot of precip you want lots of moisture. Even if you have rising motion, if it’s dry you won’t end up with a too strong of a system. A concern is if we don’t get a lot of moisture in the next few months we will start in a moisture deficit in the spring that could continue into summer. Just something to keep an eye on. Analogs Analogs are years with similar atmospheric conditions that can help us clue into what could happen. With this winter being a rare triple dip La Nina year. With the lack of good data to really depend on, I'm more inclined to look more closely at everything else. Polar Vortex The polar vortex is a large area of low pressure that exists over both poles. A counterclockwise flow of air contains it hence the term vortex. During summer it weakens and strengthens in winter. When it weakens in the winter, it can expand or split into several lobes sending arctic air south into North America causing extreme cold snaps like we saw in the winters of 2013-14 and 2018-19. These events can be triggered by a Sudden Stratospheric Warming Event which can happen a few weeks before we see effects on the surface. There are indications a lobe of the polar vortex to possibly bring down cooler air, but that is just a possibility. Solar Activity This one may seem a bit weird at first. "How does the sun affect us?" The sun runs on a 11-year cycle of low activity called a solar minimum and the period of high activity is a solar maximum. Its a measure of the number of sunspots and the strength of suns magnetic field. Changes in solar radiance could cause long-term changes in Earth's climate like the Little Ice age for instance, but not as much in the short term. We are due for the next solar maximum in 2025 while the last minimum was Dec 2019. Computer Modeling Arguably what I look at the most is computer modeling. Computer models take the very hairy nonlinear partial differential equations called the primitive equations and do the very complex math. There are two general types of models, deterministic and ensemble. Both start with the current state of the atmosphere as a starting point and work from there. Deterministic models like the GFS, ECMWF, NAM, HRRR, UKMET, etc. They are one solution that is good in the short term and in high detail, but get increasingly fraught with errors the farther out the forecast. Small errors just snowball into even bigger errors (the butterfly effect) to the point most output past more than ten days I will call "fantasyland." Ensemble models are many forecasts (or members) in one where each starts with a slightly different set of starting conditions. Deterministic models are better at forecasting the shorter term (0 hours to around 6 days) while ensembles like the GSFS and EPS are better at looking at the general pattern at the longer term. You always still need to take straight model output with a grain of salt and dont take it at face value. This is where all these other variables come in. I think I will continue my outlook in another blog post before this one becomes too much of a read.
We have managed to survive our first big heatwave. Pretty much the entire state saw a high temperature above 90, but the incredible humidity present spiked the heat index into the triple digits triggering issuance of excessive heat warnings for several consecutive days. Earlier I said that there is the possibility of periodic clusters of thunderstorms riding up and over ridges of high pressure. That did occur last Monday. A derecho did form to our north and produced hurricane force winds, Ft. Wayne reported a gust of 98 mph. Locally we saw some thunderstorms form in the warm sector of the system, though quite a few did become severe-warned, not much came out of them. as the ridge temporarily backs off at times, we can continue to see occasional ring of fire type patterns at times which can come with the chance for severe weather. Much of my forecast from earlier this month seems to be panning out. We look to remain warm into this week and early next week with virtually no chances for rain. Our best chance for rain over the next two weeks is early tomorrow and Sunday. Don't worry our next heatwave this week will not have as much humidity as earlier! An omega block pattern has set up, which is hard to change. An omega block is an atmospheric pattern where a center of high pressure is stationary and blocked in by low pressure on each side. The low in the west is actually drawing in tropical Pacific moisture letting the southwest monsoon (which fun fact, is not technically a monsoon) to continue and the southwest desperately needs rain. The high pressure on the other hand has set up shop across the midwest and eastern half of the US causing a hot, dry pattern to continue. I am concerned about drought in western Indiana. Right now we are in a deficit of soil moisture. You may ask, Elliott why am I concerned with if the soil is wet or not? Same breeds same. For every day without rain, the soil loses around 0.25" of moisture. A dry soil tends to exacerbate heat and dryness and make it worse in a vicious cycle. Its possible flash-drought could occur. Flash drought is set in motion by below-normal precipitation, accompanied by abnormally high temperatures, winds, and/or solar radiation. This time of year, we have the most direct sun angle of the year. Basically the higher up in the sky the sun is, the more insolation or solar radiation can make it to the surface. The US drought monitor shows an area of abnormal dryness for an area of western Indiana and eastern Illinois. Essentially the darker the color, the worse the drought status. Some of the worst drought right now in the United States are in the southwest. I recently spend two weeks out west for a university geographic field study so I experienced the profound dryness first hand especially in eastern new Mexico. Here is data for the Midwest. it is clear, eastern Illinois and western Indiana is in a rain deficit. Notice what the Urban-Champaign area looks like on all three graphics. It is actually expected that parts of the state will end up in drought status. Based on available data, I believe at least part of the state will end up in drought based on the current pattern. I will go ahead and include the CFS monthlies for the rest of the summer. Above average temperatures still likely and average to below average precipitation as well.
Welcome to meteorological summer! Now is the time of year we may be able to start to get the tropics affecting our local weather and statistically speaking June is when we see the most severe weather on average. For a little fun here is how 2022 is going in terms of severe weather to date. We are right in the middle of the pack in terms of severe thunderstorm and tornado warnings combined statewide on average. We started June with close to average temperatures and below normal rainfall amounts. There was quite a bit an uptick in local severe weather during the month of May (of which I was home for none of it :( since I was out west for a field class.) The next week looks to be average to cool temps and wet in general. Both the GFS and Euro models keep the high pressure to remain to our west through mid-month will keep the hotter air bottled up there. The CFS weeklies back up this idea. Our best chance for rain this week will be today. We could see some showers Wednesday and Friday into Saturday, but right now Monday looks to be the wettest day of the week. Overall, most areas of the state could receive around an inch of rain this week. Right now, it is important to get some rain. I will get a bit into why later So what about the rest of the month? I will attach the CFS weeklies heading into July. This week again looks cool to average with wet conditions then we flip midmonth to a drier hotter pattern thanks to a strengthening and growing high pressure system to our west. There is a possibility that as the heat dome expands we could get into a ring of fire pattern which would bring more chances of rain and severe weather. We need rain to ward off the possibility of drought. I can Definity see the possibility of at least a couple heatwaves later this month. The first week of July looks about the same. It is still way too early to give a forecast for Independence Day weekend, but I will venture a very preliminary forecast of warm temps at least. July overall looks similar to June with extended periods of warm to hot temperatures with below normal rainfall. If we stay dry in June and high pressure develops, I could see even hotter tempers possible at times. Dry areas and ridges of high pressure especially this time of year is the perfect recipe to get at least one 100+ deg F day. August could bring a bit of a pattern change. The western ridge eases up a bit and we may enter the ring of fire that brings us more rain and severe weather chances. My big worry is that the hot and dry conditions could lead to drought. At the moment the state is running between +4 inches and rain and -2 inches departures for the year thus far. That isn't a lot of moisture to withstand a prolonged dry period. One thing is the tropics look to be busy this season so if we can get some tropical moisture up into the Midwest that could really help farmers out a ton.
This will be a bit of a different blog post today. Normally I talk about our local weather and climate and their patterns. Today I will be writing on an area I have a large interest in, the connections between anthropogenic climate change and severe weather (here and here.) I was inspired by the severe weather in December which were followed by a media frenzy on the freak severe weather to end 2021 and how the changing climate caused them. I'll talk about whether they were unique and how severe weather can change with the warming climate. Let's get into some of the basics on climate change before moving forth. Back to BasicsFor one thing, global warming and climate change are technically different things. Global warming is simply the rise in global air temperatures, while climate change is the change in climate over time due to the global warming. Greenhouse gases like CO2, water vapor, Methane, among others helps trap heat radiating off the surface after its absorbed as incoming solar radiation. Without these greenhouse gases, the earth would essentially be locked in an unending ice age. Now of course too much of a good thing could be a bad thing as well. From the first graphic you can see with more atmosphere carbon comes higher temperatures and more CO2 has been pumped into the atmosphere since the dawn of the industrial revolution. in 1770 the concentration of CO2 was 278 ppm and now it sits at 417 ppm. There are other climate drivers, such as volcanic eruptions, variation in solar output (solar cycles,) and variation in Earth's orbit (Milankovitch cycles.) Greenhouse gases are the biggest driver though. With higher temperatures, glaciers recede and melt which adds to sea level rise in a positive feedback loop. The idea of climate change is somehow still being debated, but I am not here to debate. The scientific consensus is that human activity is the primary driver of modern-day climate change. The climate has always changed through our understanding of past greenhouse gas concentrations in ice cores, and tree rings. There have been large upheavals in earth's climate like during the medieval warm period, the little ice age, and after large volcanic eruptions, but what we are seeing today is of our own doing. Now on to the basics of severe weather. There are many types of severe weather, but for sake of brevity we will be focusing on severe convective weather (thunderstorms and tornados.) For thunderstorms you need three main ingredients, moisture, instability, and lift. For severe thunderstorms we add a fourth ingredient, wind shear. First you need a high dewpoint which means there is plenty of water vapor to form clouds. Next you need the instability or warmer air near the surface and increasingly cooler air the higher you go up. Warm air is less dense than cold air, so a parcel of warm air wants to rise (convection.) You can get a parcel of air to rise on its own when its really warm like in the summer, but a boundary like a cold or warm front, even mountains can help lift the parcels up. Wind shear is the change in wind with height. It can either be change in direction and/or speed with height. When you get the updraft of a severe thunderstorm to rotate it becomes known as a mesocyclone and found in supercells which is the type of thunderstorm most tornados come from. It can also tilt the updraft which helps a storm survive longer as the cold downdraft doesn't choke out the warm updraft too early. The two most important ingredients are CAPE (Convective Available Potential Energy; a measure of Instability) and wind shear. Now time to look at how climate change could affect severe weather. I will apologize in advance if I get a bit technical, I will try and break down everything that I can. Connections and the FutureI should preface this that since that severe convective weather is the least understood of severe weather, so it's hard to put into relation with climate change which is a very large scale process. We understand extremes in temperatures and precipitation with the future implication of climate change. We still don't understand severe convective weather too well since its so small scale, so its quite hard to understand the effect of climate change on the future. Tornados and thunderstorms for that matter are pretty small (on the order of mesoscale to microscale) and can't be seen on global or climate models. It takes high resolution models or convection allowing models like the HRRR or NAM3k to see even general shapes of thunderstorms. Models like the NAM or GFS use what is called parameterization to simplify the very fine process that cause thunderstorms. All that to say our current gridded climate models cant make out thunderstorms so climatologists and meteorologists have a work around. We know the two main ingredients for severe weather is instability and wind shear, so we can infer that days with both of those could produce thunderstorms. A big question is with a warming climate, could we see more severe thunderstorms. Studies normally account for increased greenhouse gas emissions and mean temperature increase between 2 deg C - 6 deg C through the 21st century. A basic principle with warm air is that it can hold more moisture. You could have a day with 100% humidity in the winter, but it stills feels bone dry since cold air just can't hold a lot of water vapor. With more water vapor in the air and boundary layer, we can see an increase in instability. More instability can help with more convection and stronger updrafts in storms. As for the other component, vertical wind shear. Several papers found that levels of CAPE (instability) increased, but indices of high vertical wind shears values decreased. This doesn't mean chances of severe weather go down. Chances would actually go up, with more days with high instability values. You really need a balance between instability and shear, and as long as both are present in some amount, there is always the possibility for severe weather. Now back to why I wrote this blog post. With a clearly higher than average number of tornados in December 2021. While it is obviously usual to have severe weather in the winter months, severe weather can happen all months of the year. Since thunderstorms need instability so it makes sense that most December tornados are relatively close to the Gulf of Mexico along with wind reports. There do seem to be hotspots around population centers like Jackson, MS. As I said earlier its not uncommon to have quite a few tornados reported in the month of December. With warming winters, there is the possibility of seeing more tornados on average during winter months, including December. According to NOAA "the likelihood of a tornado occurring on a December day in the U.S. is 12-15%. By contrast, the likelihood of an early June tornado is 90%. And although they are not as common, December tornadoes can still cause significant damage. Since 1879, 22 EF-4 and EF-5 category tornadoes — the most destructive — have occurred in December."
The point is that you should be on guard any month, not just spring or summer and there is a possibility that more severe weather could occur with a changing climate through extreme climate attribution. |