Severe Weather Threats for Central Plains Monday-Wednesday

After a start to a 2018 tornado season which has featured numerous tornadoes across the Deep South and even scattered tornadoes out West, but not a single tornado in Nebraska, Kansas or Oklahoma, it appears near certain the tornado drought for the Great Plains will come to an end early next week. Something which as been missing thus far…pattern favorable to severe for widespread severe thunderstorms across the Central and Southern Plains…will ramp up beginning Monday across the High Plains, shift eastward Tuesday with a peak higher-end risk for more widespread severe storms Wednesday. The jet stream, the river of air separating the cold Arctic from the warmer mid-latitudes will send a major trough of low pressure over the Western US, temporarily cooling that region down, warming up the Plains, bringing in greater moisture from the Gulf of Mexico and setting up the ingredients for multiple days of severe storms.

 

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European Model forecast depiction of trough of low pressure in the upper-atmosphere over the Western US (forecast for 7 am CDT Tuesday May 1st). This system will contribute to severe weather for the Great Plains Monday-Wednesday.

A brief review since it’s been forever since the Plains have had severe weather and there might finally be something in my neck of the woods. Severe weather is defined by the phenomena. In the US, the criteria, which weather warnings revolve around are 1) large hail of 1 inch or larger, 2) damaging wind gusts of 50 knots/58 mph or higher or 3) a tornado. Severe convection (thunderstorms) needs three major ingredients to maximize their potential. 1) Instability, 2) Moisture, 3) Wind Shear. Instability is positive buoyancy (tendency to rise). This is aided not only by heat, but also by moisture as moist air is less dense than dry air at the same temperature. Wind shear is the change in speed and direction of the wind with height. Winds which turn and increase in speed rapidly with height can promote storm rotation, allow them to form isolated cellular structures called supercells. These can be long-lived, self-maintained and produce the most intense severe weather.

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Schematic of a classic supercell thunderstorm.

Of the three days I’m most concerned about for severe weather this week, Wednesday appears to be the most serious for the Central/Southern Plains for significant severe weather. But let’s take a quick look at all three days.

Monday, April 30th-

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The National Weather Service Storm Prediction Center has a Slight Risk of severe weather (2/5 on the scale) for much of the high plains from Texas through Kansas and then, extending farther eastward into Central/NE Nebraska into SE South Dakota. This covers a 15% chance of severe thunderstorms within 25 miles of a point. A more “Marginal Risk” exists surrounding it. This would be for the afternoon and evening hours as a weak disturbance moves out of the Rockies, increasing wind shear and temperature-based instability (upper-atmosphere cooling relative to warming near the surface…warm air rises into colder air) modestly for isolated severe weather. Large hail and damaging winds are the primary hazards, but moisture will be limited, keeping the event from being widespread.

Tuesday, May 1st-

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Beyond Day 3, there are now categorical outlooks, only probabilities. A 15% chance of severe thunderstorms within 25 miles of a point exists over Eastern Nebraska, Western Iowa, much of northern and Central Kansas into Western Oklahoma. This will likely be a bit more vigorous event from Monday, with the Tuesday disturbance being stronger with better shear profiles, more low level moisture available, and the combination of abnormally warm temperatures and higher moisture will mean higher atmospheric instability for tall, intense thunderstorms with strong updrafts. The storms will likely begin as supercells across Nebraska and Kansas before merging in the evening into an organized structure known as a “mesoscale convective system”. Basically a larger scale complex which can bring locally heavy rain and extensive damaging wind gusts. The initial storms will form along a cold front and threaten damaging winds, large hail and an isolated tornado.

Wednesday, May 2nd-

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Wednesday is currently the most serious day for severe weather, but some uncertainty still exists. A 30% chance of severe thunderstorms within 25 miles of a point exists from extreme SE Nebraska, across much of Kansas, into western and central Oklahoma. A greater 15% area extends beyond  that, including my area of Lincoln, NE. Wednesday, the main upper-level trough of low pressure over the West (seen in the above map) begins to shift eastward and a surface mid-latitude cyclone sets up over the central and southern  Plains. A dryline (boundary separating warm, moist air from the Gulf of Mexico to the east from dry desert air from the Southwest US) will be located north-south somewhere over central KS/OK with a warm front either over Southeast Nebraska or Northeast KS (this is in question). The ingredients overall suggest robust thunderstorms forming along the dryline and near the area of low pressure (at the the intersection of the dryline and warm front) either in the afternoon or early evening Wednesday which vigorous supercells capable of producing large hail, some significant, damaging winds and multiple tornadoes. A possibility exists for a few of the tornadoes to be strong (EF2+; see more about the Enhanced Fujita Scale) and because of the persistent upper-level dynamics and buoyancy, storms could last after dark, posing nocturnal hazards. Later, storms will eventually merge producing greater high wind and heavy rain threats. Isolated flash flooding could be an issue Wednesday night from any heavy rain events.

For me personally, the the greatest threat for severe weather Wednesday seems to be to my south, but given the lead time, I’m watching to see how the position of the warm front ends up. If it migrates northward in the forecast and my areas is more solidly in the “warm sector”, then we will be just under as much of a hazard as the current 30% area is now. However, I note from forecast experience that warm fronts in severe storm events are notoriously challenging to forecast for as even the day of the event as they can have difficulty moving as far northward as expected because of the cold air they must erode out ahead of them. Much can also depend on the storms the previous day and how they effect the overall regional environment (temperature profiles, areas of instability, position of fronts, etc). But Monday-Wednesday all have potential to be hazardous days with Wednesday being a more potentially significant tornado day after months of silence.

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European Model forecast depiction of Precipitable Water at 7 pm CDT Wednesday (how much atmospheric moisture is available for precipitation in an instantaneous moment). This does not say how much will fall, but just how moisture laden the atmospheric column is. The plume of abnormally high PW will mean the potential for storms with locally heavy rainfall.
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European Model forecast depiction of dew point temperature at 1 am CDT Thursday May 3rd. Dew point is a measure of atmospheric moisture. The air behind the warm front and ahead of the dry line is warm and moist (with dew points above 60 F at this time), while the air ahead of the warm front is cool, with less moisture. The air behind the dry line is extremely dry and warm (dew point temperatures in the teens and 20s F).
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European Model forecast simulated upper-atmospheric water vapor imagery for 7 pm CDT Wednesday. The computer model simulates what the weather satellite water vapor channel may see Wednesday night as far as cloud structures. Water vapor imagery is a special type of infrared imagery where water vapor concentration in the upper atmosphere can be detected based on its “brightness temperature” (upper atmosphere is moist, it appears bright, upper atmosphere is dry, it appears dark, meaning water vapor is warm, located at lower level of the atmosphere). Here, the water vapor imagery is enhanced with colors to better interpret the temperature of the condensed water (clouds). We can see intense thunderstorm formation over Kansas at this time (likely supercells) with some further development into Oklahoma as well. This is NOT LIKELY how it will look exactly Wednesday evening, only a general idea of the storm structures based on the larger-scale flow pattern and expected ingredients for storm formation.

So stay tuned early next week. The weather will definitely be news yet again this Spring! Stay safe and be ready this week in these regions!

–Meteorologist Nick Humphrey

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If you want to know what to know what an “extreme weather day” is…look to today.

Today/tomorrow’s mid-latitude cyclone on the Great Plains and Midwest will be a powerful one and one which will provide something for everyone. Blizzards, wind, severe storms, flash flooding, fire…pick your poison, Nature will provide.

In places like Minneapolis and much of Nebraska, this storm threatens to be a historic late-season April heavy snow or blizzard event. In the southern Midwest and South, it threatens heavy rain, flooding and a tornado outbreak. On the southern Plains, strong winds and arid conditions, could further yesterday’s extreme fire behavior. Stay safe out there folks!

A reminder, I will be interviewed on the internet-based program Environmental Coffeehouse at 9 pm EDT/6 pm PDT tonight! A livestream will be available on their public FB page (so you should be able to see it regardless of whether you have a FB page or not). I will discuss abrupt climate change and increasing extreme weather events and how current events (ocean heatwaves, changing jet stream, etc) connect to our rapidly changing climate.

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The beast of an extratropical cyclone over the Great Plains today.
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Progression of the Great Plains/Midwest Cyclone Friday-Saturday.
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Probability of at least 4 inches of snow during the 24 hr period.

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Moderate Risk of severe thunderstorms (Level 4 out of 5) over Central and Southwest Arkansas and extreme northwest Louisiana and small portion of East Texas. Multiple tornadoes possible in the region, with isolated strong tornadoes. Damaging winds and very large hail also possible across a larger region from Iowa southward.

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Moderate Risk (Level 4 out of 5) of Flash Flooding across much of central and southern Arkansas into far northern Louisiana based on possible 1 to 3 inch rainfall rates.

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Extremely Critical Fire Risk (3 out of 3) from southern and Southwest New Mexico into West and North Texas and and western Oklahoma. Conditions exist for extreme fire behavior. Threat is being enhanced by winds associated with today’s cyclone.
If you’re wondering why all this is happening…VERY amplified…or in other words…very wavy jet stream pattern bringing extremely cold air (by April standards) down from from Canada to meet with up with extreme warm air (again by April standards) up from the south. Temps in 20s and 30s to the north with a high of 101 in Western Oklahoma yesterday to the south. Right now Lincoln, NE (where I am) is hitting 80 degrees for the first time this year. Tomorrow, Lincoln will peak in the mid-30s with falling temperatures!

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Massive long wave trough moving over the High Plains from the intermountain West of the US. The trough dips as far south as extreme northern Mexico.
The front end of this trough caused the development of the surface cyclone over Nebraska, intensifying deep moisture movement from the Gulf of Mexico (which, by the way, as a moisture source region, is running well above normal to start the year) and as and providing the deep vertical wind shear (rapidly increasing wind speeds with height) need to generate sustained severe thunderstorms. A recipe for a multi-threat mid-latitude frontal system. And it will not stop anytime soon. Saturday night, the threat will spread eastward, where a significant ice storm event may be possible for portions of upstate New York. In fact, Saturday afternoon, there may be much of Pennsylvania in the 70s while much of Upstate New York may be in the 20s! Incredible temperature contrasts for such a relatively higher latitude location.

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One model depiction (North American Model) show significant temperature contrasts over relatively short distances along a warm front near the PA-NY border Saturday Afternoon. NAM is a colder solution and there are disagreements on where freezing rain line may end up, but any major freezing rain this late in the season in Upstate New York will be quite unusual.

—Meteorologist Nick Humphrey

 

Stay safe out there today! Severe storms likely and in progress.

Nebraska is in the ice box still…but big storms, including tornadoes and significant straight line wind damage possible in parts of Indiana and Kentucky today.

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Warm, moist air, and lots of vertical wind shear. Good set up for some nasty severe weather.

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Prominent severe weather threat is between the polar and subtropical jets (northerly and southerly branches, respectively). In between, lots of mass is being removed allowing for storms to explode from below, intensify rapidly and maintain themselves in the highly sheared environment (winds rapidly increasingly with height).

There is a lot of speed shear, but not as much change in direction with height, which favors lines of storms. So the threat for damaging winds is quite significant, hence the “moderate risk” (4 out of 5 on the overall scale by the Storm Prediction Center) for a 45% chance of damaging wind reports within 25 miles of a point within the given region, and a 10% or higher chance of winds over 74 mph (hurricane-force). However, a significant tornado risk also exists for storms which do isolated themselves earlier this afternoon. So remain vigilant if you are in these areas and tell anyone you know to remain ready to take cover this afternoon and evening!

My part of Nebraska?

Unseasonably cold. Just straight up…cold. Starting off spring as if it were February with temperatures 25-30 degrees F below normal for highs and 15-20 degrees below normal for lows. Will have some recovery later this week, but near normal conditions (+-5 degrees F) don’t appear consistently likely until early next week. Thursday may give us a one day break with mid-50s (normal is around 60 F). So far our warmest day this year was March 3rd (73 F). The Great Plains have been part of the very wild weather pattern impacting much of the mid to upper mid-latitudes this year thanks to a highly oscillating jet stream with periods of very cold and very warm conditions relative to local norms. Much of Europe has gone through the same with very cold Arctic air mass spells, while the parts of the East Coast had record heat in February, followed by multiple cold and heavy snow periods from damaging nor’easters. All while the Arctic roasted in heat waves in this winter (relative to their norms) has significant heat and moisture moved northward, hitting sea ice hard. Here in my locality, we’ve had the roller-coaster ride of going from a a high of 4 to a high of 56 in ten days (January), a high of 22 to a high of 65 in seven days (February; and actually the high was 58 two days before that high of 22…ha!) to our mid-May days in early March (low-70s). Now after the last 5 days of March in the more seasonable 50s to low-60s, we’re spending the first three days of April barely above freezing. Winter was wild and Spring is starting off confusing weather even by spring standards. At least it’s not record breaking cold, it is unusually cold regardless though. Looking forward to the actual warmth of spring again.

High Amplitude Jet Stream Pattern To Lead to Extremely Abnormal Temps for Central/Eastern US; “Blow Torch” Heat to Arctic.

The US will be a land of extremes as a high amplitude jet stream…the story of this winter continues to impact the US as very abnormally cold temperatures impact the Central US and (later) the Great Lakes region, with very abnormal heat spreading northward into the Eastern third of the country mid-week. Sunday, much of the Great Plains were experiencing temperatures 20-25 degrees F above normal (~10-12 degrees C). As the week progresses, the jet stream amplitude over North America will intensify and bring highs of 30 degrees F (15+ C) or greater above normal mid-week to the Ohio and Tennessee Valleys into the mid-Atlantic and New England states. This means mid-Spring highs on the East Coast and a resumption of well below freezing temps over the Central and Northern Plains.

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In addition to the abnormal temperatures, another major story will be potentially heavy rainfall across a wide swath of the Midwest and Deep South ahead of the accompanying cold front which will push eastward mid-week. Abundant moisture from the Gulf of Mexico will aid in the generation of rainfall, some of which will help short term drought conditions, but could also produce flash flooding.

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Moderate risk of flash flooding over portion of Texas, Oklahoma, much of Arkansas and southern Missouri Tuesday.
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Tuesday evening forecast surface map showing widespread moderate to heavy rainfall likely from Texas to Michigan.

The Arctic Ocean has been experiencing an extraordinarily warm winter with consistent high heat to the region (relative to regional norms). As a result, sea ice has been suffering severely as the combination of high amplitude high pressure ridging and ocean cyclones push heat, wave action and wind into the sea ice sheet, along with very abnormal sea surface temperature right up against the sea ice (9-18 degrees F/5-10 degrees C above normal). Sea ice extent is currently running at the lowest on record in the history of human civilization, rapid melting already in progress in the northern Bering Sea, and 2017 annual sea ice volume was the lowest on record. The current max extent this season occurred on February 6th. The current earliest maximum peak extent is February 25th in 2015. The current record year for record minimum peak extent is 2017…2018 is currently beating that record and has the 2nd lowest year-to-date volume as well.

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The sea ice is showing some signs of refreezing after its early February peak. However, more extreme heat is to come as more storms from both the Bering Sea and the North Atlantic advance heat and moisture into the Arctic Ocean this week. One storm will move over far Eastern Siberia and into the Chukchi Sea on Tuesday. Wednesday, another, stronger storm will approach Greenland, moving over the Canadian Archipelago Thursday, slowly shifting toward the Beaufort Sea Friday.

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Note the last two sea level pressure images for 2/23 and 2/24. Not only the strength of the cyclone (in blue) but the tightly packed lines of equal pressure (isobars) between the low pressure system and the strong high pressure system over the Barents Sea, north of Scandinavia. These tightly packed isobars represent a very strong pressure gradient which will result in very strong southerly wind gusts (near hurricane-force) and intense wave action striking the sea ice sheet of the Arctic Ocean mid to late week. This in combination with the very warm, moist air moving into the region will make for a “blow torch” of heat from the Atlantic, eroding the cold conditions of the Arctic, stunting the freeze season further. This will likely lead to further ceasing or recession of sea ice as well.

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GFS forecast high temperature for Thursday, showing above freezing temperatures penetrating into the deep Arctic. This may continue into Friday. Today through Tuesday will feature near or above freezing temperatures moving out of the Bering Sea into the southern Chukchi Sea as well.

I’ve been tracking the Arctic all season and there has been a shocking level of persistent warmth in the region with 2-3 degrees C above normal temps (for the region) being quite common many more extreme day higher than that. The Arctic Ocean basin may experience, as a region, anomalous temperatures of an incredible 6-8 degrees C above normal Tuesday-Saturday. This is relative to the 1981-2010 average. However, as climate change is abruptly warming the Arctic region, leading to rapid sea ice loss compared to the past, relative to the late 19th and mid 18th centuries (in the early era of human generated climate change), the anomalies are likely 0.7 or 1  degree C higher than that, respectively.

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GFS Anomalous temperature forecasts for the Arctic region valid 00 UTC Feb 23rd. Extreme heat by regional standards over the Arctic for much of the week.

The implications for the collapse of sea ice are quite serious. The sea ice sheet regulates the jet stream by making the Arctic region permanently cold across a wide area. As long it it remains permanent with only modest seasonal melt, it can behave much like a continental ice sheet would behave on the atmosphere (like in Antarctica). The jet stream exists because the Arctic atmosphere is cold throughout the vertical column. The strong temperature gradient with the mid-latitudes is what makes it exist. But with abrupt warming of the Arctic caused by the collapsing ice sheet (which feeds back on accelerating such a collapse), this weakens the jet stream and has been causing it to become wavier with increasingly more extreme and frequent high amplitude patterns (which feedback and melt the Arctic more). Such research has been conducted by scientists such as Dr. Jennifer Francis of Rutgers University and others, showing the jet stream slowing and becoming higher in amplitude since the 1960s. Such abrupt warming also leads events such as “sudden stratospheric warming” and “splitting” of the polar vortex, supporting Arctic blasts to the south and abundant heat transport to the Arctic.

If the ice sheet collapses completely (no more in summer, low to little meaningful extent in the polar night), you get even more abrupt warming of the sea surface from below and above through collapse of the ocean thermocline (persistently cold water “cap” atop somewhat warmer water) and air temperature inversion (warmer air atop cold surface air) as well as from the much reduced albedo (white, reflective surface). The warming atmospheric column with height further reduces the temperature gradient with the mid-latitudes, weakening the jet further and causing more extreme “wave action”, greater blocking patterns as you get these big waves and little eastward progression of systems and the polar jet actually retreats farther north. This can dramatically shift precipitation patterns northward could cause much hotter, drier conditions in the mid-latitudes. It’s been a major concern for a long time in in climate change science, but a process thought to be of concern in the “high emissions” scenarios of the mid to late 21st century as increasing aridity across the mid-latitudes would destroy forests and not allow crops to be grown where they are currently grown because of increasing extreme heat (or storms). So this would have impacts not only in the Arctic, but also in the mid-latitudes. Unfortunately, a recent phrase has been increasing use the past few years. “Faster than expected”. Some prominent researchers openly admit an ice-free Arctic may be possible before 2020. See also HERE.

I’ll have more on the situation in the Arctic this week as well as the heavy rainfall in the US. Also, keep an eye on Tropical Storm Gita approaching New Zealand to start the week!

–Meteorologist Nick Humphrey

Cyclone Gita headed for close passage of Tonga

Cyclone Gita in the South Pacific is a powerful Category 4-equivalent tropical cyclone on the Saffir-Simpson Scale (as of the time of this post). Maximum sustained winds analyzed by the US Joint Typhoon Warning Center are up to 130 mph with gusts to 155 mph. Gita is moving westward and is expected to pass near or over Tonga around 12 UTC Monday (6 am CST or 1 am Tuesday local time). The storm is expected to be at least a powerful Category 4 storm. There is moderate wind shear (increasing winds with height effecting the cyclone and limiting more rapid intensification. However, with water temperatures along the path of 28-29 degrees C (82-84 degrees F) and well-organized structure, Gita will be a potentially catastrophic storm if its eye wall moves over the main island. Gita will also produce very heavy rain (perhaps 6-12 inches) which will lead to flooding. A state of emergency has been declared in the island nation.

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Gita (9P) moving westward toward Tonga. Visible satellite image at 04:52 UTC Monday.
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03 UTC Monday Advisory on Cyclone Gita by the Joint Typhoon Warning Center.

After 24 hours, Gita is expected to gradually weaken as sea surface temperatures cool and vertical wind shear increases as the system begins to turn to the southwest into higher latitudes. However, Gita is expected to remain a hurricane-force storm through the end of the week.

New Zealand will need to keep an eye on the remnants of Gita as the dying circulation an moisture plume may curve back southeastward in the mid-latitude westerlies. While, the forecast will certainly change somewhat…such as the position of the upper-level trough of low pressure southwest of New Zealand which will cause the system to curve back towards the country beginning Sunday…any remnant system may lead to locally heavy rainfall for both the North and South Islands early to mid-week next week.

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European Model accumulated total precipitation forecast ending 00 UTC February 22nd. The remnants of Gita are forecast to curve back southeast toward New Zealand early next week delivering very rainfall.

 

–Meteorologist Nick Humphrey

Effect of Sun-Mon Arctic Ocean Storm on Sea Ice

You may remember I posted last Friday about the major North Atlantic storm which was expected to move into the Arctic Ocean Sunday and Monday producing hurricane-force winds, 30 ft+ waves and temperatures over 40 degrees F above normal (near or even above freezing in places). Well that storm advanced through the Arctic and now noticeable effects can be seen (via satellite analysis) on sea ice concentration (amount of ice vs. open water in a given area) and on sea ice sheet growth and resulting extent.

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North Atlantic Surface Analysis valid at 06 UTC February 5th (midnight CST) showing the 958 millibar low pressure system off shore northeast Greenland entering the Arctic Ocean from the North Atlantic basin. (US National Weather Service)
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Global Forecast System model analysis valid 12 UTC February 5th (6 am CST). This shows the very strong sustained winds and (by Arctic standards north of 80N) extremely warm temperatures during the height of the storm. This was thanks to very strong warm air advection from the Atlantic Ocean. The system had a sub-tropical connection with heat and moisture originating from the subtropical western Atlantic. Average temperatures in many places should be -30 to -15 F (-34 to -26 C). (earth.nullschool.net)

Included are two images of the sea ice concentration…one I saved from the February 3rd, another just posted for February 6th. Lighter blues are for 90-95% concentration, with yellows and reds being for 75-90%.

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Extent growth basically stopped between February 3-6 (near 13,300,000 sq km for four days).

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2018 year-to-date extent (currently at record lows) vs 2016 extent (previous daily record lows for this time of year) and the 1980s average. Sea ice extent and volume collapse is underway in the Arctic Ocean because of Anthropogenic Climate Change caused by abrupt warming in the Arctic (notable since the 1980s, accelerating since the 2000s). 

More very above normal temperatures will hit the Arctic this weekend as a powerful blocking high pressure system over the Pacific (sound familiar…) raises temps once again across Alaska and allows storm tracks to head for the Bering Strait and Chukchi Sea once again. Meanwhile, the Atlantic side will continue to remain “open” with another storm also moving into the region this weekend. No storm appears to be nearly as powerful as the Sunday-Monday event, but the litany of systems bringing at least some wind, wave action and temps not far below the freezing point of salt water is no good for the Arctic.

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Temperature anomaly (degrees above or below average) forecast by the GFS model for the Arctic region valid 18 UTC February 10th (noon CST). Normal is based on 1981-2010 baseline. To approximate the major effect of anthropogenic climate change since the end of the 18th century add +0.9 degrees C (K).
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GFS maximum temperature forecast valid 18 UTC February 10th (noon CST). Very warm air temperatures on both the Atlantic and Pacific entrances to the Arctic Ocean.

Arctic sea ice is extremely important for everything from Arctic regional ecology, marine biology to effects on overall warming of the Arctic Ocean and surrounding land areas (and permafrost). There is also evidence that the rapid warming of the Arctic because of anthropogenic climate change is altering the polar jet stream circulation which may be leading to an increased frequency and magnitude of extreme weather events. 

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Sea ice thickness and thickness anomalies in January 2018. (Zach Labe)

–Meteorologist Nick Humphrey

 

 

Wild Ride – More Cold Intrusions into North America/Europe, Powerful Warm Storm Headed for Arctic Ocean Monday

This winter has been a fascinating one to say the least. Wild oscillations between very abnormally warm and very abnormally cold while other places are are just consistently very warm. Or perhaps just very dry. Much of this has been thanks to the current La Nina pattern in place over the Tropical Pacific. The atmospheric pattern leading to abnormally cooler waters over the eastern tropical region also lead to the promotion of strong high pressure systems over the Central North Pacific with unusually higher amplitude jet streams. This favors a polar jet aiming for the Pacific Northwest, northern tier and into the northeastern third of the country while the Southwest and Sunbelt see drier conditions.

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Conditions of at least “Abnormally Dry” cover over 67% of the Continental US. It is the most coverage in abnormally dry conditions since February 5, 2013. It is, interestingly, the 49th greatest extent of at least Abnormally Dry conditions on record out of 944 recorded weekly updates (over 18 years now). Conditions of at least D1 “Moderate Drought” coverage over 38% of the Continental US. It is the most coverage in D1 conditions since April 22, 2014.

Of note with this pattern regime has been the, at times, extreme nature of the jet stream amplitudes. They have driven very warm temperatures into the Arctic with record low sea ice across the Arctic Ocean, the warmest December on record across the state of Alaska, and record high temperatures in portions of the Southwest US in January with the aforementioned persistent drying and intensifying drought concerns. 

Meanwhile, significant Arctic intrusions have been impacting the US, particularly in January and more appear likely in February as “teleconnections”…patterns in global circulation which give clues toward a general weather regime for a region of the world…show signs of further intense extreme jet stream amplitudes with very strong upper-level high pressure systems blocking storm tracks over the north Pacific and Bering Sea, which downstream will mean a cross polar flow in the upper atmosphere of very cold air upper troughs and surface Arctic fronts and high pressure systems over northern Plains/Midwest into the Northeast US. The Deep South should escape as warmer air from the subtropics attempts to advance north and may keep the Arctic air at bay. Europe looks to also have periods of similar cold (and interior Siberia of course! Check out the incredible cold they had last month).

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Temperature Anomalies in the US (Sunday, Thursday) and in Europe (Monday). Widespread temps below freezing during the day in parts of central and Eastern US and central and eastern Europe during these cold periods. Very persistent warmth with highs in the 60-80s in the Southwest US.

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Powerful Arctic Ocean Storm Sunday-Tuesday

While the mid-latitudes get hit with Arctic cold, the Arctic is being pounded by significant amounts of mid-latitude heat. And now the computer models are pointing towards a major North Atlantic storm developing early this weekend, moving over Greenland and then into the middle of the Arctic Ocean Sunday night-Monday. This storm will be very powerful…as strong as any classic North Atlantic ocean winter storm, and will bring significant amounts of high winds, battering waves and high “heat” to the Arctic. How warm? Perhaps as warm as 50-60 degrees F above normal temperatures over much of the Arctic Ocean. This will mean highs near or just above freezing up to the North Pole!

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Temperature forecast by the Global Forecast System model for noon CST Monday showing near or above freezing temperature penetrating deep into the interior Arctic as a result of intense warm air advection.
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A significant sector of the Arctic Ocean will have air temperatures over 40 degrees F above normal (or higher) during the day Monday.

This storm is forecast to initially form southwest of the tip of Greenland and east of Quebec Friday and will beginning moving over Greenland Saturday. Sunday, the system will begin to impact the Arctic, with warm and moisture transport from the North Atlantic (all the way from the Azores!) increasing abruptly late-Sunday. By Monday morning, models indicate waves moving up the Fram Strait toward the Arctic may be as high as 30 ft in strong south-southwesterly flow. Over the sea ice sheet, the low pressure system will be intense as it emerges from Greenland…possibly sub-960 millibars with widespread wind gusts of up to hurricane-force likely over much of the interior Arctic Ocean east and south of the low on the Atlantic side.

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GFS depiction of the powerful low pressure system over the central Arctic Ocean on Monday. The European model has a similar strength low. Winds up to hurricane-force wind gusts and battering waves are likely conditions for the tenuous sea ice.
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Forecast significant wave heights for early Monday with the worst of it in the Fram Strait.

Why this storm is so significant is because the Arctic sea ice is continuing to undergo collapse because of anthropogenic climate change. If the Arctic climate warms to the point that it simply cannot support sea ice in the warm season, with the Arctic Ocean warming as a result of very low albedo (reflectivity to visible light which would otherwise limit warming) compared to white ice (or latent heat of melting/freezing, instead of heat going into warming the ocean directly), this will have dramatic effects on not only regional climate but global climate (I can go into greater details in this in the comments or provide resources). Generally this was something expected much later in the future, but may occur earlier than expected, although it is difficult to predict when exactly this will occur as it would be nonlinear and abrupt. However, as mentioned, ice volume and extent for ice are running at record or near record lows across the Arctic Basin. Some of these effects on albedo and heating have already begun to be felt over the past several years on the marginal seas which are beginning to become increasingly ice free during the warm season (Chukchi Sea, Beaufort Sea, Eastern Siberian Sea), but it’s important to not have the interior Arctic Ocean lose significant ice. Particularly in the winter, but it has been struggling just to freeze this winter! For more on recent sea ice developments see these videos by Paul Beckwith (M.Sc, PhD candidate; HERE and HERE).

In the meantime, while we have year to year variability…various teleconnection patterns, anthropogenic forcing (CO2, other gasses) is the most dominant regime on our climate and so even while I must emphasize weather is not climate…I must also emphasize that climate is a statistical distribution of weather events; and so extreme weather events which are increasing in frequency and magnitude are a sign of our climate shifting to more extreme conditions and in sensitive places (particularly cold climates like the Arctic), those shifts are incredibly noticeable.

–Meteorologist Nick Humphrey