Major Pattern Change for North America and Arctic Next Week.

A major weather pattern shift will be occur next week for North America into the Arctic as the jet stream…which already has been largely higher in amplitude and experiencing some blocking with little eastward progression of long-waves in the upper-atmosphere, will becoming extremely amplified (north-south) next week bringing very warm air up into Alaska, Yukon and the Arctic Ocean and a modified Arctic air mass from Nunavut and the Northwest Territories of Canada into the central US. Let’s take a look at things.

The current pattern dominating North America has been strong ridge of high pressure over the Western US or Eastern Pacific with a prominent trough over the eastern US with some fluctuation in the wave pattern east or west, but not much significant change, except in the center of the country which has seen more significant swings between these two states. The east, including even the Southeast saw significant snow. The west has seen abnormal warmth with record fires in California. Currently the ridge of upper-atmosphere ridge is forecast by US and European models to build to an extremely high amplitude the end of next week north over portions of Alaska and Yukon and into the margins of the Arctic Ocean. This as a very intense trough is forced south over the US.

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European model forecast for the wave pattern of the mid-level atmosphere valid 6 pm CST 12/23.

This extreme amplification will drive an Arctic surface air high pressure system out of the Northwest Territories with very cold air this week, with this air mass advancing into the US beginning Thursday into this weekend. Meanwhile stormier conditions will moving from the Bering Sea into the Chukchi Sea driving up temperatures in the far north. And California with all the fires? Remains abnormally warm and dry.

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Temperatures the afternoon of Christmas Eve (European Model forecast).
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Greatest signal for low to no precipitation the next 10 days is south-central to southern CA into much of AZ and NV.

The Arctic:

As I spoke about in a previous post, the Arctic is having its second warmest year on record and lowest annual sea ice volume on record as climate change continues to abnormally warm the Arctic. The highly amplified wave pattern is much a product of the current weak La Nina pattern. However, the intensity of the amplification and resulting amplified warming of the Arctic is also a function of the long-term global warming regime dominating the polar region and causing record warmth and reductions in sea ice. I noticed this amplified wave pattern will have interesting impacts on the Arctic weather pattern and possibly the tenuous sea ice beginning next week.

Right now, a prominent surface high pressure region…associated with the Beaufort Gyre…is over the Arctic Ocean north of Alaska and eastern Siberia. By the middle of next week, this gyre will weaken as strong low pressure systems approach the Arctic from both the Bering Sea and the far North Atlantic.

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Prominent high pressure of the Beaufort Gyre over the sea ice of the Arctic Ocean.
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European Model depiction of low pressure system advancing into the Arctic Ocean from the Bering Sea on Christmas Eve. This may be the strongest in a series of lows (2-3) beginning late week. Stormy conditions will also impact areas near Svalbard (islands just east of northeast Greenland) late-week and weekend.

The Gyre is vulnerable because of the areas of open water and tenuous sea ice which remains over the Chukchi Sea…record low extent for this time of year. The ice being cold creates the surface high pressure system and clockwise circulation. But last year, this gyre collapsed because of slow sea ice growth allowing for storms with warm, moist air to move into the Arctic and further slowed sea ice growth. It appears this may be forecast to happen again during the tail end of this month.

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European Model forecast surface temperatures showing well above normal temps shifting northward late week into Christmas Eve over the Arctic Ocean north Svalbard and the Chukchi Sea. While exact values will change, general pattern appears likely.

Depending on the strength of the low pressure systems, not only will the tenuous sea ice in the Arctic…widespread areas 1.5 meters or less in thickness (less than a meter in the Chukchi Sea)…deal with more warm air temperatures limiting sea ice growth, but also wave action which may destroy the ice, particularly from the Pacific side as cyclones are expected to move across the Arctic from the Pacific. We’ll see how much impact those storms have and how intense they are. If the upper-level wave pattern is as amplified as forecast by models 5-8 days out (no reason to think otherwise as he reach the point of good reliability for the upper-atmosphere), it’s a good set up for strong low pressure systems to develop in both the North Pacific and North Atlantic. And with the highly amplified blocking high over the Eastern Pacific, storms will be forced to track into Alaska and into the Chukchi and Beaufort Seas and deep Arctic Ocean.

–Meteorologist Nick Humphrey

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La Nina Pattern Begins in the Pacific Ocean

A weak La Nina atmosphere-ocean pattern has fully developed in the Pacific Ocean. This phenomenon is part of the cool phase of the El Nino Southern Oscillation (ENSO). It is characterized by abnormally low surface pressure in the Western side of the Pacific Basin and abnormally high pressure on the Eastern side. This causes an enhancement of the easterly trade winds, causing significant upwelling of cold water along the equatorial coast of South America, with a build up of very warm water in the Western Pacific.

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Schematic of La Nina oceanic ocean-atmosphere pattern in the Pacific and expected jet stream behavior and temperature/precipitation impacts in the US/Canada during a La Nina winter.

ENSO patterns, as shown above can cause noticeable changes in the seasonal weather patterns over North America, particularly during the winter months. The jet stream can become more amplified, leading to a Pacific jet producing cooler and wetter than normal conditions over the Pacific Northwest, extending into the northern tier states. Meanwhile, the “Sun Belt” of the US can see abnormally warm, dry conditions.

The caveat of all this is is the strength of the La Nina versus the degree of influence other atmospheric patterns have on the seasonal climate variability. Other patterns include the North Atlantic Oscillation (NAO-surface pressure variability between the semi-permanent Icelandic Low and Azores High), Arctic Oscillation (AO-pressure anomalies between Arctic and mid-latitudes, closely related to NAO), and the Madden-Julian Oscillation (which can speed the development and enhance the effects of a El Nino or La Nina phase), among others on various timescales.

So what does it mean for our winter in the US? Well, as of now, the NWS Climate Prediction Center is generating winter temperature/precipitation forecasts accounting for the development of La Nina, with a strong latitudinal effect on temperature and precipitation. Below/above in the north and above/below in the south, respectively.

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In the meantime, long-range forecasts show the North Atlantic Oscillation becoming “negative” later in November (characterized by a south to north pressure gradient between the Azores high over Portugal and the Icelandic to the north). This pattern is favorable for an amplified upper-level jet stream wave pattern over North America and the North Atlantic and intrusions of cold air deep into the eastern half of the US. So in the shorter term colder than normal conditions may be possible for these areas this month (as has already occurred this week).

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When it comes to these “teleconnections”…the various cycles of variability within the annual climate regime of Earth…they can most definitely give us a head’s up on to what to expect in general. A canvas of how the weather may be behave over the course of days to weeks and months. But we must keep track of how these different cycles interact with each other and how they vary individually in terms of strength and mode. One curiosity is the strength and persistence of the La Nina. If it was fairly weak, it is more likely to be dominated by other teleconnections at times during the course of the winter, versus if it intensifies and produces more persistent effects on the upper-level air patterns.

Overall, the expected winter pattern is good news for drought-stricken areas in the northern tier such as Montana and the Dakotas. We will have to watch areas along the southern tier for potential further drought development. And as mentioned, November and at least early December could feature a more amplified jet stream so that even areas in the Southeast which may end up with an above average winter overall may see serious impacts from cold because of Arctic intrusions (something for citrus growers to watch out for in Florida, for example).

–Meteorologist Nick Humphrey

GOES-16 Satellite Loop of California Wildfire Smoke

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The new geostationary weather satellite, GOES-16 captured this high spatio-temporal resolution loop of the smoke plume over the Bay Area of Northern California this evening before sunset. The deep smoke is embedded in the low-level north winds, while the white, high cirrus clouds are in southwesterly flow. You can right click to save or open in the new tab to see the larger version of it. It’s amazing but frightening to know what’s happening under all that smoke.

–Meteorologist Nick Humphrey

JPL 2017 Eclipse Simulator

Anyone want to know what the 2017 Eclipse will look like at your location with nice graphics and all? Check out this excellent simulator put together by NASA’s Jet Propulsion Laboratory. You’ll be able to animate the eclipse for any given location in the US from beginning to end and find out what to expect. I made a collection of some of the locations which will experience partial eclipses (all at their time of maximum eclipse). All these location were in areas of 75% or greater obscuration of the solar disk. Optical and atmospheric effects begin to take hold with 75% obscuration as incoming shortwave radiation from the sun is significantly reduced. Read more about that in my previous July post HERE if you haven’t already. Remember, however, that even with 99% obscuration, the sun will still be too bright and therefore too dangerous too look at directly without certified eclipse glasses. Direct viewing of the sun for multiple minutes can blind you, any amount can cause eye injury!

Seattle
Seattle, WA. My home city! 92% Obscuration.
Portland
Portland, OR. 99% Obscuration. So close to totality, yet so far!
San Francisco
San Francisco, CA. 75.5% Obscuration.
Denver
Denver, CO. 92% Obscuration.
Brookings
Brookings, SD. The location of my undergraduate alma mater South Dakota State University. 89% Obscuration.
Minneapolis
Minneapolis, MN. My Mom and much of my extended family lives here. They’ll take in the show. 83% Obscuration.
Dallas
Dallas, TX. 75% Obscuration.
Atlanta
Atlanta, GA. 97% Obscuration.
DC
Washington, DC. 81% Obscuration.
Jacksonville
Jacksonville, FL. 90.5% Obscuration.

Additional eclipse info for this post (such as max eclipse time) is courtesy of Xavier Jubier’s 2017 Total Eclipse Interactive Map.

Hilary and Irwin making plans for a Fujiwhara waltz over the open ocean

Let’s learn something cool about the tropics!

The past couple of weeks, the Eastern Pacific Basin has been quite active with multiple active tropical cyclones churning, dying and new ones forming. All while the North Atlantic Basin has been largely silent. We’ll get into the pattern set up for tropical activity between the two basins in the coming few weeks in a moment. But first, let’s discuss two interest systems in process in the EPac – Hilary and Irwin.

(Intensities are as of 4 pm CDT Thurs)

Hurricane Hilary is currently a Category 1 with max winds of 75 mph moving to the west-northwest. Meanwhile, ~480 nautical miles southwest of Hilary is Tropical Storm Irwin. It has max winds of 60 mph and drifting westward. Neither system is a threat to populated land masses and both are quickly heading for cooler waters north of the subtropical Pacific, where much drier air also exists in the mid-levels of the atmosphere. Both will lead to rapid deterioration of the cyclones this weekend.

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Visible satellite image showing Tropical Storm Irwin and Hurricane Hilary in close proximity at 4 pm CDT July 27, 2017. Cooler waters are noted to the north producing stable air mass near the sea surface, including deep marine stratus clouds and “closed cell” cumulus cloud deck. Stable air mass is non-conducive for thunderstorms hurricanes need to sustain themselves.
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Same image at same time as above in the “water vapor” infrared channel, where mid-level water vapor is detected. The circled area is a fairly dry area where air is experiencing sinking motions, coinciding with the cooler surface waters and the lack of thunderstorm activity for deep atmospheric moisture. Deep dry air can disrupt thunderstorm activity in tropical cyclones and weaken them.

Later Sunday and into Monday, an amazing phenomenon is expected to occur. Because of the very close proximity of Hilary and Irwin – only several hundred miles apart – the two cyclones are expected to undergo a Fujiwhara Interaction. This describes when two vortices in close proximity begin to rotate around a common center or one around another if one is more dominant. It is named after the Japanese meteorologist Sakuhei Fujiwhara who first described the interaction scientifically in a 1921 paper.

It does not happen very often, but it is typically more common in the Western Pacific basin where a very large surface area of favorable tropical development and maintenance exists and many cyclones can develop simultaneously and sometimes in close proximity.

Numerical models have shown the possible interaction for days.

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The slideshow above displays the Hurricane Weather Research & Forecasting Model forecast initialized at 11 pm PDT Wednesday with the forecast valid 5 pm PDT Sunday – 11 am PDT Monday. This model is “nested” on Hilary to show its evolution (the colors are surface temperatures in degrees C and wind barbs are in knots). However, you can see Irwin orbiting around it on its south and east sides Sunday evening – Monday morning. Irwin will likely weaken and die (along with Hilary, not long after), or will become absorbed by Hilary.

Nature never ceases to amazes in what it can do with the laws of physics!

 

Northern Plains becoming hard hit by severe to extreme drought

The Northern US Great Plains into the southern Canadian Prairies are suffering from a growing drought problem. The National Drought Mitigation Center at the University of Nebraska-Lincoln released their weekly drought monitor which updates on the drought situation for the entire country (every Thursday based on Tuesday data). Drought overall across the United States has begun to grow in coverage and intensity. This can happen just from the local abnormalities in a summer season. However, a persistent pattern of dryness has developed over the Northern Plains beginning in May where significantly below normal rainfall has caused soils and hydrologic sources to begin to dry out.

I took a look at some meteorological stations for their recent climate records. Rapid City, SD (currently in the moderate drought zone) is running 3.37 inches below normal in rainfall for the May 1st-July 21st period. In Bismarck, ND (in severe drought) is even worse at 4.01 inches below normal for the same period. May dryness hit the region hard with a major monthly deficit then it simply continued into the summer. At least moderate drought covers ~28% of the above region (ND, SD, NE, KS, WY, CO). Moderate conditions can result in some damage to crops and reduction in stream/river flows and lowering of lake levels. Extreme – which now exists in spots of southwest ND – can mean widespread and devastating agricultural losses and severe reductions in hydrologic sources.

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Above average temperatures likely over the Great Plains (and rest of the country) over the next 3 months. (Climate Prediction Center)
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Meanwhile, there are equal chances (~33% each) for above, near, or below normal precipitation during the same 3 month period. (Climate Prediction Center).

Obviously, “equal chances”- which is based on the expected evolution of various climate patterns – means that there could very well be above average rainfall, which the region really needs at this point to get out of the growing deficit. However, if it ends up being near-normal, they may continue to simply lag behind with similarly bad impacts. Below normal means a worsening and spreading of drought conditions and further difficulty removing the existing drought (anyone remember the difficulty California had in getting out of drought?). Folks in these areas should be prepared for any further water restrictions and do what they can now to conserve in case the dryness lasts longer than expected.

Elsewhere, dryness and moderate drought has begun to spread into parts of the Intermountain West and Four Corners.


Quick update from the Eastern Pacific tropics…new tropical depression! Tropical Depression Ten-E is rolling around between Tropical Storm Greg and TD Nine-E. It’s expected to become a tropical storm in the coming days as it generally moves westward over the open ocean. So there are now 4 existing cyclones in the tropical North Pacific east of 180 longitude. Although Fernanda is dying quickly over cooler waters and dry mid-level air and will likely dissipate by tomorrow.

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Good weekend to you all!

Intense heat dominating Central US; Active Eastern Pacific Hurricane Season continues

Welcome to the inaugural post of Weather and Climate News! There’s much going on this week, but the most significant has been the intense heat over the center of the country as very strong high pressure system has entrenched itself over the region. This, in combination with dew points of 70-80 degrees, was allowed for heat indices of 105-115 degrees F to steam much of Plains, Midwest and Deep South. This, while periodic areas of thunderstorms, some severe, form around the periphery of the clockwise high pressure system. Heat advisories and excessive heat warnings are in effect today as a result of the potential health hazards of the heat.  Be safe and drink lots of water! Particularly in areas with heat or heat indices in the triple digits when you may be outdoors for long periods.

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Analysis of features over the United States (July 21, 2017).
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National Weather Service Forecast map for 7 pm CDT Saturday evening. The cold front will depress the intense heat and humidity over the Central Plains, restricting it to the Southern Plains and Midwest.

The intense heat will relax a bit over the Central Plains this weekend as a result of a “cold” (more like cool?) front with temperatures closer to seasonal norms.


The Central and Eastern Pacific is quite active with the tropical cyclone activity! Eastern Pacific activity can of course impact Mexico, but (more typically later in the season) enhance the Southeast US monsoon with either additional atmospheric moisture for afternoon thunderstorms or (rarely) move ashore Mexico or into the United States as an organized tropical depression or weak tropical storm. Today, however, neither country has any issues from any of these systems today. Three to be exact, with a four likely imminent. All of these cyclones…Tropical Storm Fernanda (born in the East, but now in the Central Pacific west of 140W longitude), Tropical Storm Greg, and Tropical Depression Nine-E are all moving away from major land masses and populated areas.

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The Eastern Pacific Basin (defined as 140W east to the continents and north of the equator) is running ahead of schedule in terms named storms to date (7), hurricanes (3) and major hurricanes…defined as Category 3 or higher strength (2). Fernanda was at one point the most intense hurricane of the season in the Eastern Pacific with maximum winds of 145 mph on July 14-15.

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It’s now a shell of its former self and while it’s heading in the general direction of the State of Hawaii, it should continue to weaken dramatically as it encounters drier mid-level air and cooler waters. High surf and hazardous rip currents are the biggest threats to anyone doing recreational activity around the Big Island the next couple of days as the dying system moves to the north.