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.

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.

Temperatures the afternoon of Christmas Eve (European Model forecast).
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.

Prominent high pressure of the Beaufort Gyre over the sea ice of the Arctic Ocean.
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.

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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Arctic Sea Ice Extent Rapidly Decreasing Because of Climate Change; Weather & Climate Implications

Today, NOAA presented the State of the Arctic report at the American Geophysical Union annual conference in New Orleans. The news from the report was devastating for potential weather and climate impacts. Lots of important info to talk about from this! Let’s summarize:

  1. Annual Arctic sea ice extent is the lowest in 1600 years. This is based on proxy data (tree rings, lake sediments, ice cores from the Greenland Ice Sheet). There has been an abrupt decrease in extent during the 20th century (continuing to present). 24991395_10215050817330895_108575701643656859_n
  2. Arctic sea ice extent reached a record minimum in the warm season in 2012. However, 2015-17 witnessed consecutive record low maximum extents in the cold season. 2016 also had the lowest extent on record in November or December. 2017 is also witnessing top two or three low daily extents in November into December, with record low sea ice in the northern Bering Sea and the Chukchi Sea (north of the Bering Strait between Alaska and Russia). Also very notable, sea ice VOLUME (which includes thickness of ice) has continued to suffer with 2015-17 in the top 4 for the lowest volume on record going back to 1979 (and based on decreasing of sea ice extent and thickness, likely much much longer than that). Multi-year ice…ice more than a year old…is now nearly extinct in the Arctic Ocean.

    Arctic Sea Ice Volume since 1979. Note consistent and accelerating collapse of sea ice volume. Arctic ice volume may fall below the 2012 record at some point in the month of September in the next several years.
  3. The Arctic had its warmest year on record in 2016 and its second warmest year on record in 2017 in reliable records. The climate of the Arctic is warming to the point that permafrost is increasingly melting releasing methane and carbon dioxide, methane emissions from what are called methane hydrates (methane gas locked in water ice) are increasing from the very shallow continental shelves surrounding the Arctic Ocean and mid-latitude weather patterns are becoming altered because of reduced sea ice (more on this shortly). The Arctic tundra is also greening at an increasing rate because of rapid warming.
  4. NOAA specifically states that “the Arctic shows no signs of returning to a reliably frozen region of recent decades” because of continued climate change related warming.

Discussion – Leaving the Ice Age Era:

One thing that we must remember about the sea ice of the Arctic Ocean (and the Southern Ocean around Antarctica) is that sea ice is a product of Ice Age eras. Our planet has had a tendency historically to flip between two global climate equilibrium states with dramatically different regional weather and seasonal patterns. The Ice Ages and the Hot House “Jurrasic Park” climates have been the two long-term dominating climate regimes in Earth’s history. One characterized by huge ice sheets and low sea levels, the other characterized by no ice sheets, no sea ice and high sea levels. Human civilization has flourished in the latest interglacial period in the Ice Age era because the climate has remained largely stable for roughly 10,000 years (-1 to +0.5 degrees C relative to mid-20th century climate) and mild enough to for extensive agriculture and settlements.

Estimated temperature of Planet Earth from 550 million years ago to the end of the 20th century.

But now, because of Anthropogenic Global Warming (AGW) from climate change, we are leaving that stability in the geologic blink of an eye.

Projected rise in global temperature of 4 degrees C/8 degrees F (relative to mid-20th century) during the 21st century relative to the past 10,000 years.

Probably the most important regulars of climate during Interglacials are the “refrigerators” of the north and south…the Arctic Ocean sea ice and Antarctic Ice Sheet (also Greenland Ice Sheet). However, as temperatures warm because of human carbon dioxide emissions trapping heat in the global climate system, that heat warms the atmosphere and ocean, attacking the sea ice by providing excess latent heat of melting. For the Arctic, this reduces the sea ice extent and volume decade after decade. Eventually, it will get to a point, where sea ice will become so thin and tenuous, it will undergo collapse to what has been called a “blue ocean” event with 1,000,000 sq km or less ice at a minimum in September (2012 extent minimum record was 3.41 million sq km). The 2016 and 2017 extent minimums were in the top 10 with 4.14 and 4.64 million sq km, 2nd and 8th respectively. 8 of the top 10 warm season minimum extents (in km) have occurred since 2010 in the now 39 year record. The Arctic Ocean and lower atmosphere are warming and becoming more like the high latitude North Atlantic. Eventually sea ice is expected to disappear completely in the warm season in the Arctic. Some climate scientists have suggested over the past several years that the “blue ocean” event resulting from a collapse of sea ice extent could occur between 2015-2020 or so as multi-year ice has nearly gone extinct, leaving thin ice vulnerable to quick melting and battering waves from cyclones. Computer models have been terrible at dealing with the end of sea ice in the Arctic, suggesting it would stick around into the second half of this century.

Discussion – Weather and Climate Implications:

So why does loss of sea ice matter? Sea ice regulates the climate of the world in multiple ways. It acts as large white surface which reflects most of the shortwave solar radiation from the sun (high albedo). As a result, it keeps the Arctic and Northern Hemisphere (and world) cooler than otherwise. It’s wide physical presence means heat entering the Arctic Ocean goes into melting the ice in the warm season (latent heat of melting; heat goes into phase change of water from solid to liquid) instead of heating the ocean and atmosphere dramatically (sensible heat to change temperature). Losing sea ice ends its presence as a climate regulator, allowing for more abrupt warming of the atmosphere-ocean system and increasing moisture content in the atmosphere (water vapor is an additional greenhouse gas; and increased clouds may reflect some radiation, but also can limit cooling in darkness). In addition, the Arctic Ocean will warm as it is a dark surface (low albedo). Increasing ocean warming in the marginal seas of the Arctic Ocean is already leading to increased methane emissions from the shallow continental shelves (as subsea permafrost thaw the clathrates) and more rapid warming will lead to an increase in emissions of methane and carbon dioxide from land permafrost (see discussion by Arctic climate scientist Dr. Peter Wadhams of Cambridge University on YouTube). Methane is over 100 times more powerful greenhouse gas than carbon dioxide on a timescale of several years (it dissipates far faster in the atmosphere, but sudden releases can increase warming quickly). And all of these feedbacks will much more quickly destroy the sea ice extent through further warming for a longer period in the warm season until ice disappears completely.

Increased warming of the Arctic also has impacts on mid-latitude weather. There has been research suggesting that the jet stream can be strongly influenced by Arctic warming and sea ice extent (see discussion by Dr. Jennifer Francis on YouTube). This can include a weakening of the upper-level jet stream which depends on the temperature difference between the upper-level mid-latitudes and polar atmosphere (known in meteorology as “baroclinic instability”). This weakening can lead to the jet stream developing high-amplitude waves more frequently, allowing for powerful upper-level ridges of high pressure to develop and cause blocking of the progressive westerly flow. This blocking can cause more frequent stagnant weather for locations, developing droughts in some areas through prolonged dryness, long periods of heavy precipitation in other regions as well as places of very abnormally warm temps (greater extreme summer heat) vs. colder temperatures (but the warmth always significantly outpaces the cold). Increased warming of the atmosphere in general also increases rainfall rates. In addition, paradoxically, while parts of the mid-latitudes may go through below normal temps and cold weather, the powerful ridging can produce extremely abnormally warm temperatures over the Arctic regions, intensifying the warming of the far north.

An identical pattern to this has largely set up over the Northern Hemisphere November into December.

Powerful high-amplitude ridges over the Eastern Pacific and North Atlantic. Pattern relatively stagnant at this time.
Reanalysis of the average temperature of Earth and specified regions over the last 30 days (1981-2010 baseline…add 0.7 C to compare to late 19th century). Note extensive, persistent anomalous warmth of the Arctic.

These effects may overall lead to more abrupt warming of the world as a whole as well as (more importantly) changes in rainfall and snowfall patterns, relevant for crops and food security from increasing summer extremes (heat stress and heavy rainfall) and water resources (snow pack, groundwater, etc). Also relevant for forest health (destruction by increasing wildfires as well as bug infestations killing hundreds of millions of trees in the Western US). And a running theme in stories on climate change recently? “Faster than expected” or “Faster than previously thought”. The importance of Arctic sea ice cannot be overstated and, unfortunately, this major tipping point…which I would consider a “keystone” tipping point because of what effects it can have down the line on other parts of the climate system…seems to be on the brink. It has been 2.6 million years since significant sea ice did not regularly exist in the warm season in the Arctic Ocean.

The statistics of weather has already changed significantly because of global warming with far more extreme heat events, drought periods and heavy precipitation events than in the mid-20th century (see presentation by Dr. Aaron Thierry on shift to more extreme weather conditions; starts 12:30 min, recommend watching through 20:30 min; also see discussion of climate change on increasing extreme events by Dr. Stefan Rahmstorf). Going past tipping points far earlier than expected by climate models will increase the likelihood for far more extreme weather events as weather patterns and circulations change (in some cases difficult to predict ways). Clearly, the world still needs adequate mitigation and adaptation measures to deal with these rapid and possibly abrupt changes.

For more info into how climate change influenced global extreme weather events in 2016, see the latest report (issued today) by the American Meteorological Society with attribution studies on last year’s significant events.

–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.

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).


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

First Game of World Series Tonight…Weather Headline: HOT

The World Series begins tonight in Los Angeles between the LA Dodgers and the Houston Astros. And it begins with record heat in Southern California. Today, in fact, downtown LA is setting a record high for the day and it is the warmest temperature on record for so late in the year. This was after a record high of 102 was set for downtown LA yesterday. So far it has reached 103 downtown and the official high may be higher before the day is done.

First pitch for the World Series is at 5 pm PDT this evening. While temperatures will decrease somewhat by that time, game time temperatures will be in record territory for a World Series Game (95-100 degrees F). The hottest World Series first pitch on record was from a game (cannot remember which) in 2001 in Phoenix when the NY Yankees played on the road against the Arizona Diamondbacks in a starting game temperature of 94 degrees.

In addition to heat, fire danger remains VERY high across Southern California as Santa Ana winds intensified today and will continue into tomorrow. RED FLAG WARNINGS are in effect for parts of SoCal. Gusts of 50-60 mph have caused problems for firefighters as they dealt with brush fires in Granada Hills this morning and Rancho Cucamonga this afternoon (LA Times). 

(Map of Rancho CucamongaMap of Granada Hills)

Game 2 of the World Series (First Pitch at 5 pm PDT Wed) should be slightly “cooler”, but still quite hot…expecting temperatures to start the game in the mid-90s (92-97 degrees F). If you’re going to these games or doing any outdoor activity at all in Southern California…lots of water and be careful with anything that sparks or burns!

US Global Forecast System forecast temperatures at 5 pm PDT Tuesday.

Enjoy the game! Go American League and go Astros!

–Meteorologist Nick Humphrey

Fire Conditions expected rest of this week and weekend for California

The fire conditions Wed Night into this morning were not as severe as expected thanks to weaker winds. This allowed firefighters to make some ground against fires through the night, however high fire danger remains and will continue for days into the future, with no rain in sight.

Strengthening pressure gradients along the mountainous terrain of interior California and the warm, very dry air mass will promote high far danger with windy conditions near the mountains and adjacent valleys Fri Night-Sunday. (See tightly packed isobars…lines of equal pressure…on the map in CA just west of Nevada as high pressure shifts SE-ward over the Intermountain West).
Very low dew points during the day Sat could mean relative humidity values as low as 10-20% across interior California, along with gusty winds for high fire danger.

Air quality remains terrible in the Bay Area. Folks in that region should do what they can to avoid being outside if at all possible.

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Unhealthy air quality exists across the entire Bay Area. Expect harmful air quality to be problematic into the weekend.

I’ll add any additional updates related to fires on this post today. Stay safe in these areas!

–Meteorologist Nick Humphrey

Update on Wildfire Situation in Northern California.

The Northern California wildfires continue to rage and risk both lives and property. At least fifteen fires are currently burning across Northern California with little to no containment. The most significant fires include the Atlas Fire, Tubbs Fire, the Cascade Fire, Nuns Fire, and the Redwood Complex Fire. As of 8 pm PDT, there have been 17 deaths reported (11 in Sonoma, 2 in Napa, 3 in Mendocino and 1 in Yuba Counties). 180 people have been reported missing in Sonoma County with 57 out of originally 240 reported missing found since yesterday. More than 2,000 structures have been destroyed. 115,000+ acres have been burned with many fires at 0% containment.

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A SUV burns in the driveway of an already burned down home threatening another home in neighborhood off Fountaingrove Parkway near the Hilltop in Santa Rosa on October 9, 2017 in Santa Rosa, California. (Photo: Brian Van Der Brug/LA Times Via Getty Images).

Today, the atmospheric conditions were initially better for fighting fires this morning with higher humidity values and low winds. Winds have remained lighter today compared to previous days, but humidity has once again dropped this afternoon below 30% or even 20% in many areas in the hilly elevated terrain down into Napa Valley, allowing fires to continue to steadily spread.

Low humidity values north of the Bay Area allowing fires to more easily attack vegetation and structures. (
Very high surface particulates causing very poor to hazardous air quality over much of Northern California (particulate matter on map <2.5 micrometers). (

I wish there was more good news to give to the folks in NorCal, but unfortunately, NO rain is forecast for the region for the next seven days. In addition, the National Weather Service issued a RED FLAG WARNING for Wed Night-Thurs Afternoon as high easterly winds blowing out of the hilly terrain will produce very low humidity, allowing for potentially explosive wildfire growth.

Global Forecast System model forecast valid 1 am PDT Thursday morning showing high pressure building over the elevated terrain of Nevada and northeast California. Strong easterly downsloping winds will develop, intensifying wildfire potential.
Global Forecast System model forecast valid 1 am PDT Thursday morning showing wind gusts of 25-45 mph across north-central California.
Global Forecast System model forecast valid 1 am PDT Thursday morning showing humidity values falling below 25%, keeping fuels dry for fires to spread.

If you know anyone in or near the effected region (or in the RED FLAG WARNING areas), tell them to make sure they clear vegetation near their homes/businesses and have an emergency plan in case evacuations are issued for their area. Unfortunately, this wildfire disaster is ongoing and requires those who are in or near rural country to be ready to escape at a moment’s notice.

Live Updates by the San Francisco Chronicle: HERE

—Meteorologist Nick Humphrey

Start of October Drought and Climate Update

Nearly 14% of the Continental US is in at least moderate drought conditions right now. The most highly afflicted areas are over the northern tier states west of the Mississippi River…the Dakotas, Montana, Idaho, Washington and Oregon.


There are scattered areas of drought and abnormally dry conditions across other parts of the country. However, an isolated area of severe to extreme drought has been hitting south-central Iowa for much of the summer and there are also areas of moderate drought developing over the the Desert Southwest and eastern Maine.

The level of dryness, particularly over Western North America has promoted a significant fire season, which continues at this time. British Columbia is having its worst fire season on record and the Western US is having an unexpectedly destructive fire season. This even after much of the region had a wet winter, showing that a significant period of dryness following well-grown fuels from a wet season can still lead to a major fire season. As of October 4, 2017, nearly record 8.5 million acres have been burned in the United States in 2017.* While below the 2015 record of 10.12 acres, it should be noted that anthropogenic climate change is increasing the risk of fire seasons in the US over 3 million acres and there has been a significant increase in fire seasons of 3 million acres or more since the turn of the century. 2017 may rank in the Top 3 for fire seasons (along with 2015 and 2012). Temperatures across the West were well-above normal or record levels over the summer. Various records for heat (as well as persistence of warmth and dryness) were broken in places such as Western WA/OR, central and southern CA as well as the portions of the Interior West.

Drought Outlook for October 2017. Drought is expected to dissipate in Western WA from the incoming wet season, and improve somewhat in northeast MT. However, much of the drought in the US will persist and in fact additional areas may develop over the central Midwest and Mid-Atlantic states.
The Probabilistic Precipitation Outlook valid Oct 10-16, 2017. This suggest by mid-month, the atmospheric pattern will be favorable for drier than normal conditions over the center of the nation with near normal or wetter than normal conditions over the coastal regions. The Climate Prediction Center also shows above normal temperatures likely over the Southwest US and Eastern third of the country. Dryness will maintain or promote further development of drought conditions in portions of the nation’s interior.

As of today, the NWS Climate Prediction Center indicates a 55-60% chance that a La Nina climate pattern will develop late in the Northern Hemisphere Fall and into the Northern Hemisphere winter. This is characterized by an intensified Walker Circulation (the east-west tropical Pacific wind circulation) and intensified cold water upwelling along and offshore the coast of South America.

Weather patterns common during La Nina events include abnormally wet, cool conditions in the western Pacific Northwest and TN/OH valleys, but abnormally dry and warm conditions across the southern tier of the United States. This is partially incorporated into the monthly and seasonal drought and temperature/precipitation outlooks.


For those curious, the climate models are showing the US having a more than likely above normal winter throughout (including AK) with the La Nina-like distribution of precipitation (likely above normal Northwest, below normal Southeast). More on winter as we get closer.

*-I incorrectly stated that total acres burned in the US was around 3 million acres. (10/4/17)