Very above normal temperatures dominating US to end November

Much above normal temperatures are dominating much of the United States right now. This is largely a product of a zonal or progressive jet stream moving along the northern tier states and southern Canada locking colder air over interior Canada and the Arctic (although, I note, the Arctic is seeing much above normal temperatures relative to what they should be seeing as well!).

My area…Eastern Nebraska…has been seeing many days of 60s and even mid-70s, including today. The average temperatures this time of year should be in the low to mid-40s for highs and near 20 for lows. Instead it’s been feeling like it’s around birthday time for me. My birthday is in May.

GFS-025deg_NH-SAT1_T2_anom
Global Forecast System model analysis of surface air temperature anomalies for November 27th. The GFS tends to have a minor warm bias from reality, but it is accurate is showing significant above normal temps over the western and central sections of the United States. The baseline normal period is 1979-2000, prior to the significant amplification of climatic warming in the Arctic (occurring because of anthropogenic global warming).
gfs_namer_048_250_wnd_ht
Global Forecast System model forecast depiction of upper-air wave pattern at 250 millibars (~10,200 meters/33,500 ft) valid Wednesday morning. The jet stream will remain largely over the northern tier and southern Canada this week with above normal temps of varying departures over the US.

As we move into the first week of December, trends point to some dip in the jet stream over the Western US early next week causing below normal temperatures. However, this will also amplify the jet stream over the eastern two-thirds, producing significantly above normal temperatures yet again.

One additional thing of note. Snow cover is virtually non-existent in the contiguous US today (Nov. 27th). Only 4% of the CONUS has snow cover today. Going back to 2003, this is lowest snow cover extent for this particular date. The second and third lowest for Nov. 27th were 8.7% (2009) and 10.2% (2011). The snow cover area extents on Nov. 27th in 2010, 2012-2015 were in the range of 20-35%. 2016 was fairly low at 15.4%. The data is available HERE.

nsm_depth_2017112705_National
Snow depth analysis map for the US and southern Canada for November 27, 2017.

I don’t know date prior to 2003, however it is known that climate change is reducing snow cover extent and depth in the US and the Northern Hemisphere beyond natural variability. The aforementioned trough in the West should increase that extent somewhat next week.

Advertisements

Key Findings of the US Government’s Climate Science Special Report

Today, the US Global Climate Change Research Program released the Climate Science Special Report, Vol. 1 of the Fourth National Climate Assessment mandated by Congress to provide the latest scientific basis and impacts from climate change on the United States. Climate science continues to evolve, but in the direction of more significant realization of how humans have influenced the climate thus far, as well as how much more influence will come in the not to distant future.

Below are some of the headline findings provided in the rather powerful report (be prepared for a lot of INTENSE info):

    1. Earth’s average temperature has increased by 1 degree C (1.8 F) during the 1901-2016 period. This is faster than any rate known in the last 1,700 years.                 2017TempUpdate_Top10_Global_F_en_title_lg
    2. The average temperature of the contiguous United States has also increased by 1 degree C (1.8 F) during the 1901-2016 period. Satellite and surface observations are consistent in the detection of this rapid rise in temperature. With no change in the rate of greenhouse gas emissions, the CONUS is expected to experience a more abrupt average rise in temperature of 3.2-6.6 degrees C (5.8-11.9 F) between now and 2100.                                                                                 
      figure6_1
      Change in average surface temperature (annual and seasonal) for the period 1986-2016 since the period 1901-1960 (contiguous US; 1925-1960 for Alaska and Hawaii). Data from NOAA.

      figure6_8
      Projected changes in the coldest and warmest daily temperatures (°F) of the year in the contiguous United States. Changes are the difference between the average for mid-century (2036–2065) and the average for near-present (1976–2005) under the higher emissions scenario (RCP8.5). Maps in the top row depict the weighted multimodel mean whereas maps on the bottom row depict the mean of the three warmest models (that is, the models with the largest temperature increase). Maps are derived from 32 climate model projections that were statistically downscaled using the Localized Constructed Analogs technique. Increases are statistically significant in all areas (that is­­, more than 50% of the models show a statistically significant change, and more than 67% agree on the sign of the change). Data by NOAA.
    3. Temperature extremes in the United States are trending significantly toward record high temperatures over record low temperatures. This trend is expected to continue with the number of below freezing days also continuing to decline and days above 32 degrees C (90 F) continuing to rise.
      figure6_5
      Data by NOAA.

      figure6_9
      Projected changes in the number of days per year with a maximum temperature above 90°F and a minimum temperature below 32°F in the contiguous United States. Changes are the difference between the average for mid-century (2036–2065) and the average for near-present (1976–2005) under the higher scenario (RCP8.5). Maps in the top row depict the weighted multimodel mean whereas maps on the bottom row depict the mean of the three warmest models (that is, the models with the largest temperature increase). Maps are derived from 32 climate model projections that were statistically downscaled using the Localized Constructed Analogs technique. Changes are statistically significant in all areas (that is, more than 50% of the models show a statistically significant change, and more than 67% agree on the sign of the change).
    4. The global influence of natural variability is limited to small fraction of observed climate trends. Solar output and the Earth’s internal natural variability have contributed only marginally to the observed changes in the climate system over the past century. There is no convincing evidence for natural cycles in the observational record that could explain the changes in the climate system.                                                                                                                                                         
    5. Heavy precipitation events have increased across the US since 1901. The highest increase over the Northeast and the second highest increase over the Midwest.                                                                                                                                2017ClimateExtremes_Downpours_3_en_title_lg
    6. Northern Hemisphere spring snow cover, North American maximum snow depth and Western US snow-liquid equivalent have all declined since the early 20th century. At current rates of decline and assuming no change in water resource management, chronic, long-duration hydrological drought conditions are possible for portions of the United States by 2100.                                                                                                                                                                                               
    7. Global mean sea-level has risen 7-8 inches (~0.2 m) since 1900 with 3 of those inches since 1993. Relative to the year 2000 is very likely global mean sea-levels will rise up to 0.6 ft (0.18 m) by 2030, 1.2 ft (0.38 m) by 2050 and 4.3 ft (1.3 m)+ by 2100. A more rapid degradation of the West Antarctic Ice Sheet may mean physically possible sea level rise theoretically exceeding 8 ft (2.4 m) by 2100 (confidence is low on this).                                                                                                                2016StateOfClimate_SLR_en_title_lg
    8. The global ocean has absorbed more than 93% of the heat caused by global warming since the mid-20th century. The oceans have warmed by about 0.7 degrees C (1.3 F) during the 1900-2016 period. Assuming no emissions changes, warming of the oceans by an average of 2.7 degrees C (4.9 F) is expected by 2100.                                                                                                                                       2016StateOfClimate_HeatStorage_en_title_lg
    9. The global ocean continues to undergo rapid acidification because of dissolved carbon dioxide from atmospheric emissions. The rate of acidification is unparalleled in the past 66 million years (since the Cretaceous-Paleogene Impact Event). At the current rate, the pH of the global ocean may decline from its current average of 8.1 to as low as 7.8 by the end of the century. Seawater with pH <8 can be corrosive to shellfish, plankton and coral which depend on carbonate structures for their shells, backbones and skeletons. The greatest change in acidity will be in Arctic Ocean.

      figure13_5-1200
      Predicted change in sea surface pH in 2090–2099 relative to 1990–1999 under the higher scenario (RCP8.5), based on the Community Earth System Models–Large Ensemble Experiments CMIP5 (Figure source: adapted from Bopp et al. 2013 ).
    10. The Arctic is warming at a rate approximately twice as fast as the global average with a rapid decline in sea ice volume and extent since satellite observations began in 1979. At the current rate of warming, the Arctic Ocean will be effectively ice-free in the month of September by the 2040s.                       

      siv_annual_max_loss_and_ice_remaining
      Arctic Sea Ice Volume since 1979. Note gradual and accelerating collapse of sea ice volume. Arctic may fall below 1,000 cubic kilometers at some point in the month of September in as early as several years to a decade or so. This will happen when the yearly sea ice maximum and loss of what remains equal.
    11. Global warming has contributed “significantly” to ocean-atmosphere variability in the North Atlantic Ocean; as a result these changes have contributed to the observed upward trend in North Atlantic hurricane activity since the 1970s. North Atlantic hurricanes are expected to increase in intensity (maximum sustained wind potential) with increasing precipitation rates during the 21st century.                                    2017Hurricanes_Info_en_title_lg

      figure9_2-1200
      Tracks of simulated Saffir–Simpson Category 4–5 tropical cyclones for (a) present-day or (b) late-21st-century conditions, based on dynamical downscaling of climate conditions from the CMIP5 multimodel ensemble (lower scenario; RCP4.5). The tropical cyclones were initially simulated using a 50-km grid global atmospheric model, but each individual tropical cyclone was re-simulated at higher resolution using the GFDL hurricane model to provide more realistic storm intensities and structure. Storm categories or intensities are shown over the lifetime of each simulated storm, according to the Saffir–Simpson scale. The categories are depicted by the track colors, varying from tropical storm (blue) to Category 5 (black; see legend). (Figure source: Knutson et al. 2015; © American Meteorological Society).
    12. Large forest fires in the Contiguous US and Alaska have increased since the early-1980s. This increase is expected to continue with “profound” impacts on ecosystems.                                                                                                                           2016Wildfires_temp_WEST_en_title_lg

Some other findings of note:

-For the period 1901-2016, the Dust Bowl Era (mid-1930s) remains the most extreme era for heat. This is thought to be largely the result of significant land-surface feedbacks caused by precipitation deficits and poor land management leading to reduced vegetation and strong surface heating (which in turn promoted further drying and land degradation). However, we are on a path to eclipse this period in US climate history in the coming decades, particularly as colder conditions (more found in 1930s winters for example) continue to decline in a warming climate and extreme heat continues to increase.

-The Climate report explains (as has been explained in previous scientific literature) the period of so-called “global cooling” which occurred from the mid-1940s to mid-1960s: aerosol particles generated by WWII and post-war industrial production (esp. coal power plants) which reflected some solar radiation into space temporarily slowing long-term global warming, even as carbon dioxide concentration in the atmosphere continued to increase.

-The report notes that annual precipitation has decreased over the West, Southwest and Southeast, while increases have occurred over the Plains, Midwest and Northeast. They specifically mention an increase in mesoscale convective systems (organized clusters of thunderstorms which dump significant rainfall) over the Plains and Midwest since 1979. Mesoscale convective systems are expected to increase in frequency and intensity during the 21st century.

-While tornado climatology related to climate change has been difficult to understand because of the reliability of storm reports before the 1990s, scientists involved in the report have concluded one interesting aspect…there is moderate confidence in a decrease in tornado days (day when tornadoes of any number are confirmed), as tornadoes are increasing on those days. Greater volatility in tornado occurrence year-to-year as well as a trend toward an earlier first occurrence during the year have been observed. Studies looking at the ingredients for severe storms with all modes of potential activity (tornadoes, hail, wind) suggest an increased frequency and intensity of severe storms over areas prone to them in the US in a warmer world, but confidence on details is low.

-This report concluded that observed drought and precipitation increases (1901-2016) cannot be confidently attributed human-induced global warming. The Dust Bowl Era remains the benchmark period for extreme drought conditions. However recent negative trends in soil moisture are believed to be attributable to warming temperatures. Although soil moisture projections in climate models are still considered in their “elementary” stages in the science, based on what is known, there appears to be a signal for further decreases in soil moisture over portions of the US (particularly West and Plains) by the end of this century, increasing the risk of chronic hydrological drought.

-I find the key finding #11 I listed particularly important. There has been much debate between scientists (particularly more observational minded meteorologists vs. climatologists) about whether there has been truly observable increase in N. Atlantic hurricane activity seasonally beyond the natural variability, given the limited period of reliable satellite record and intensity measurements. This statement is given MODERATE confidence given that global warming has caused increases in sea-surface temperatures, oceanic heat content and natural cycles on multi-annual and multidecadal time scales involve changes in not only these thermodynamic variables but also dynamic ones in response (vertical wind shear, position/intensity of monsoon troughs, development of tropical waves into organized TCs).

Additional Thoughts:

This slideshow requires JavaScript.

Climate change will likely be one of the most difficult challenges the world will face this century (at least). Why? Why should we care?

When it comes to effects on people (which is what people care about), at the end of the day, what matters for the livelihood of people rich or poor? Food, water, living space. If these become challenged, you get human suffering (from economic to health threats) and geopolitical problems. The potential for significant drying and increasing chronic hydrologic droughts from loss of snowpack will lead to increasing populations in demand for resources seriously straining water resources. Crops around the world will face increasing difficulties from heat stress, prolonged droughts mixed with periods of more intense heavy rainfall events. Acidification and warming may threaten marine food resources already strained by overfishing around the world. Living space will become slowly threatened by sea level rise in low-lying areas and island nations…and more readily in the coming decades…by repeated far more extreme heat waves than previously in already hot, humid environments where cooling is not readily available, and possibly by diseases as ecosystems shift to different places, along with pests (which will also impact crops potentially).

Climate change isn’t just about warming, it’s about cascading impacts on the whole of the climate system. Without a drastic global shift to a low-carbon energy sources and the advancement of technology to remove carbon dioxide from the atmosphere, we are in store for a very challenging period in human history. This isn’t worse-case/best case or any of this. This is simply the path that we are on, no over-dramatic statements nor downplaying needed or tolerated. Hopefully we via our governments make the right choices.

–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_model-en-087-0_modusahd_2017102418_6_1870_210
US Global Forecast System forecast temperatures at 5 pm PDT Tuesday.

Enjoy the game! Go American League and go Astros!

–Meteorologist Nick Humphrey

WxClimoEd Series, Post #1, Part 2: Understanding Global Climate Change Indicators

Hello Weather & Climate News readers! This post will be the first (Part II) in what will be my ongoing education article series WxClimoEd. I hope to write educational posts on various topics related to weather and climate to help enhance your understanding of various phenomena and their impact on the environment, individuals and society. These posts will present key ideas and concepts and provide occasional linked sources to further, more detailed information.

Understanding Global Climate Change (Indicators)

In Part 2 of this article series on Global Climate Change, I’ll discuss the indicators of climate change in progress on  Earth. Even without the global measurements of temperature, there are plenty of signs in the climate system that change toward a warmer world is in progress.

IMG_3897

Earth Undergoing Abrupt Climate Change

While global warming is considered to be detectable since the First Industrial Revolution (after 1750), since the latter half of the 20th century, the environment has begun to exhibit what could be considered “abrupt” changes. Among scientists who study natural abrupt change in the paleoclimate records have had some common thought on what “abrupt” means: 1) Changes in climate which can be witnessed within a human lifetime and 2) the change is very nonlinear; it far exceeds the mechanism which initiated the change in the first place (See this video presentation by Dr. White at the American Geophysical Union Annual Meeting discussing past abrupt climate change in the paleoclimate record). In the past, abrupt change usually occurred as a result of the advance or recession of ice sheets, leading to rapid change in local temperature or regional circulations (or even global distributions of precipitation or temperature patterns). Today, abrupt change is being increasingly witnessed as a result of an already unnaturally fast mechanism (rapid rise in carbon dioxide concentration, resulting in rapid rise in global temperatures relative to natural variability…multi-decadal to centennial  scales vs. multi-millennial).

Here are just some of  the abrupt changes resulting from the changing climate happening now:

  1. Decline in sea ice over the Arctic Ocean

siv_annual_max_loss_and_ice_remaining
Arctic Sea Ice Volume since 1979. Note gradual and accelerating collapse of sea ice volume. Arctic may fall below 1,000 cubic kilometers at some point in the month of September in as early as several years to a decade or so. This will begin the process toward widespread open ocean in the Arctic for a time in September.
2. Rapid increase in air temperature of the Arctic.

The Arctic (64-90N) has warmed around 3-4 degrees C since the 1881-1910 period (based on NASA data). 2-3 degrees C of warming has occurred just since the 1951-1980 period with notable warming since the year 2000. This has led to not only the rapid decline in Arctic sea ice, but the beginning the melting of land permafrost.

temps
Average air temperatures (over land and ocean) in the Arctic region, relative to 1951-1980 average. Shown is 1984 (year I was born) to 2016. Red box show rapid warming of Arctic since 2000 compared to previous decades. “315” = +3.15 degrees C anomaly. (NASA GISS)
Addendum: The rise in the average temperature of Earth as a whole can count as abrupt, as seen in the earlier graph (farther back up). Most warming has occurred since the 1970s. The top ten warmest years on record going back to 1880 have occurred since 1998 (with 1998 now the last year in the top ten from the 20th century). 2017 is expected to be the 2nd warmest year on record just slightly behind 2016.


3. Increase in Sea Surface Temperatures and Oceanic Heat Content of Global Ocean.

The average sea-surface temperature of the global ocean from 60S-60N has risen around one degree C since the 1881-1910 period. 0.5 degrees C warming has occurred since 1980. Like the global air temperature, SSTs have been most of their record warm years since the turn of the 21st century, with an accelerated pace of warming since 2000 (1.62 degrees C/century currently, compared to 1 degree C/century 1950-2000). 2017 sea surface temperatures are currently running the 2nd warmest on record (NOAA data).

ssts
Sea surface temperature anomalies 1880-2016 for various sectors of global ocean. Values on graph are in degrees F. Oceans have warmed roughly 2 degrees F/1 degree C.
As far as oceanic heat content, the oceans have accumulated over 100 zetajoules (1 x 10^23 joules) of heat energy in the upper 700 meters of the global ocean since 1993. An incredible amount of energy, with increasingly accelerated warming in the deep ocean below 700 meters since 1993.

4. Acidification of the Global Ocean.

Earth’s seawater is slightly basic (basic is ph > 7). The global average ph of the oceans has decreased from 8.25 to 8.069 since the 1750s (ph was 8.104 in the 1990s). This is caused by the oceans dissolving carbon dioxide (30-40% of carbon dioxide released by humans dissolves in the oceans). This interaction forms carbonic acid, with further chemical reactions leading to increasing concentrations of the hydronium ion (H+). This leads to a lowering of the ph. The rate of acidifcation is faster than at anytime in the past 300 million years! The rapid acidification has been more pronounced in the Arctic Ocean because of very cold water (colder water can absorb more dissolved gases). When ph falls under 8 in the coming decades (assuming no mitigation), marine life which depend on carbonate structures (shellfish, sea snails, corals, some types of plankton, etc) begin to suffer from the corrosive effects of less basic waters.

5. Sea Level Rise

rate-of-sea-level-rise-accelerating

Sea levels are rising as a result of meltwater from land and thermal expansion as oceans warm. As the atmosphere and oceans continue to warm and weaken the Arctic and Antarctic Ice Sheets, sea levels will continue to rise, with possible nonlinear positive feedbacks accelerating it. It has already accelerated since the end of the 20th century. “King Tides” have become an increasing problem because of sea level rise in the 21st century.

6. Increase in Extreme Weather and Climate Events

The end of the 20th century into the early 21st century has featured a statistical increase in extreme weather events. Climatologists usually classify “extreme” as being 4-5+ standard deviations from the mean of all events. Such increase in extreme events over the course of years means that natural variability is being dominated by global warming, and causing a continuously shifting climate pattern.

unnamed
The shift in the range of meteorological variables across the bell curve because of climate change. The curve represents the normal distribution of events with natural variability (climate teleconnections and seasonal). The small shift of the mean by climate change causes a significant increase in less common events at one tail as well as an increase in truly extreme events not previously observed in the reference climate regime. (Presentation slide by Erick Fernandes, 2015).
Extreme events include heat, flooding, rainfall rates, drought, and wildfires. All of these occurrences have been increasing the frequency and severity around the world because of climate change. In addition, there is evidence that because of the high rate of warming of the Arctic, the mid-latitude jet stream has become weaker with increased amplitude extremes, leading to short-term and longer-term patterns favorable for extreme conditions at the surface. For example, high amplitude ridges of high pressure which do not move much or reform constantly can lead to extended periods of drought and extreme heat (while other areas downstream may receive cooler temps but heavy rainfall and flooding. This is actually something that is observable on meteorological timescales. Dr. Stefan Rahmstorf discusses the increases in extreme events from climate change in a lecture HERE.


One thing I must emphasize with understanding the impacts of global climate change is that it is impacting the environments of our world now and continue to accelerate in the coming years and decades (assuming no major changes are done). Global warming…the primary force of climate change, caused by our immense release of greenhouse gasses from fossil fuels…is the dominate force behind the rate of change in climate behavior. According to the Intergovernmental Panel on Climate Change in their 5th assessment, the world should actually be experiencing anomalous COOLING right now, but instead we have warmed Earth above and beyond natural long term global temperature variability. So when people ask “Did global warming cause (insert extreme weather event)?”, it is the wrong question. Climate looks at a collection of events for a trend. What is clear is that global warming is NOW causing a statistically significant increase in extreme events and will continue to do so. There is no “new normal” but only a continuous “ramping up” of the Earth’s natural variability toward greater extremes relative to the beginning of the Industrial Revolution, with greater impacts as humanity leaves the stable global climate in existence since the beginning of civilization.

This may be something many do not appreciate, but it is factual. Human civilization has changed Earth’s climate system to the point that we as humans are turning up the “thermostat” and started a multi-centennial experiment in geoengineering. Heat, drought, flooding, rainfall rates, wildfire events, and jet stream amplitudes, as a result, have all increased significantly in just the past 30 yrs.

If the climate were a piece of music…think of Earth’s relatively short-term natural cycles as the melody and global warming as the dominating background harmony from which the melody plays over. If the harmony changes keys, the melody will respond and shift accordingly.

In Part 3, I’ll discuss the projected future impacts of climate change being actively researched (and some already happening) such as food security, human health and living space.

Firestorm devastating portions of Napa Valley, CA.

Sunday Night, major fires erupted in California’s Napa Valley under strong easterly winds and low relative humidity. This resulted in a conflagration engulfing communities and homes in flames and forcing thousands to make quick escapes in the early morning hours. One of the worse hit communities is Santa Rosa, where much of the city has been destroyed by fire. Over 1500 homes and businesses are believed to have been burned down in the Napa Valley region. The flames continue to grow at this time with over 75,000 acres burned.

Photos via the San Francisco Chronicle.

The fires are occurring in a region which is currently not in drought conditions hydrologically (as of last Thursday). However, after an unusually wet winter, an unusually hot, dry season followed. This allowed fuels, which grew in abundance following the wet season to dry out, leading to the massive fires in CA in this summer going into the Fall. Much of Western North America has been suffering significant fires in 2017 (year-to-date acreage burned in the US, as of Friday, was 3rd to 2012 and 2015). Intensifying wildfire seasons (on regional/continental scales) and increasing frequency of large fluctuations in extremes between very wet and very dry periods are predicted signals of climate change from global warming as well.

january-to-march-2017-us-total-precipitation-percentiles-map
Much above average to record precipitation in Northern California in January-March 2017.
august-2017-us-total-precipitation-percentiles-map
Much below average to record minimum precipitation (including NO measurable rain) in Northern California in August 2017. June-August 2017 saw much below average precipitation.
august-2017-us-average-temperature-percentiles-map
Much above average and record warmth across the West Coast during August 2017. San Francisco Bay Area saw record highs over 100 degrees at the start of September.

So far the fires have killed 10 people (as of 10 pm PDT Monday Night), while more than 110 have been injured, some severely from burns, most from smoke inhalation. It’s being reported Monday Night that 100 missing persons reports have been called in to the Sonoma County, CA office.

920x1240
Region where fires are in progress in the San Rosa and Napa region far north of San Francisco and west of Sacramento.

Although relative humidity conditions will improve somewhat tomorrow, no rainfall is forecast for this region of Northern California for the next 7 days to dampen the fire situation. Winds Tuesday will likely gust over 20 mph and may be locally stronger near the fire, continuing the self-sustaining burn.

us_model-en-087-0_modusarpd_2017101004_2_1900_219
11 pm PDT Monday Analysis by the High-Resolution Rapid Refresh (HRRR) showing the low dew point temperatures near and east of Santa Rosa. This area delineates a region of low relative humidity, allowing fires to burn and spread with little moisture on fuels to slow their extent.

 

For further updates see this updating page by the San Francisco Chronicle.

–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.

20170926_conus_text

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.

month_drought
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.
814prcp.new
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.

lanina-winterPNG

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)

Hurricane Harvey continuing its march toward Texas

My goodness…7-day rainfall forecast…and much of that in Texas and Louisiana is over 3-4 days…

The hurricane is still expected to make landfall somewhere over the south-central TX Coast near borderline Category 3/4 intensity tomorrow night. Evacuation orders are underway for many coastal locations and barrier islands for potential significant surge up to 12 ft above normal levels. Hurricane warnings are up from Port Mansfield to Sargent, Texas with a tropical storm warning from south  of Port Mansfield to the Mouth of the Rio Grande River at the US-Mexico Border.

This continues to be a potentially catastrophic storm. Incredible freshwater flooding will likely be the main story but storm surge and perhaps even wind damage could be additional impacts. Please tell anyone you know in these areas to take evacuation notices seriously. 

I’ll have frequent updates on Twitter and Facebook with occasional updates on WordPress. Visit www.nhc.noaa.gov for the latest updates from the National Hurricane Center.