WEEKLY CLIMATE NEWS

22-26 October 2018

• Debunking the legend of the woolly bear caterpillar and winter severity -- The long-held folklore legend that the size of the band on the midsection of the woolly bear caterpillar in early autumn can be used to forecast the severity of the upcoming winter is described and shown to be a myth. [National Weather Service Forecast Office, La Crosse WI]
• Accessing the national climatographies -- NOAA's National Centers for Environmental Information (NCEI) and its predecessor, the National Climatic Data Center, have produced numerous climatographies that are quantitative descriptions of climate that include tables and charts portraying the characteristic values of selected climatic elements at a station or over an area. Some of these climatographies provide a variety of daily, monthly and annual normal climate data for agricultural, transportation and other interests. This week's Supplemental Information...In Greater Depth provides the links to selected climatographies from NCEI.

CURRENT CLIMATE STATUS

• National weather and climate reviewed for September 2018 -- Scientists at the NOAA National Centers for Environmental Information (NCEI) recently reported on their analysis of preliminary weather data collected during the month of September 2018. Based upon these data, this recently concluded September was the fourth warmest September across the contiguous United States since sufficiently reliable climate records began in 1895. The nationwide monthly average for September was 67.8 degrees Fahrenheit, which was 2.9 Fahrenheit degrees higher than the 20th century (1901-2000) average. The relatively high temperatures were driven by warm nights, as the minimum (nighttime) temperature averaged across the "Lower 48" States was the second highest September temperature on record, while the daily maximum (daytime) temperatures across the country was the 23rd highest.
  Most (42) of the contiguous states reported above to much above statewide average temperatures for the month. Seven of these states (Arizona and Utah in the West and Delaware, Florida, Maryland, Ohio and West Virginia in the East) had record high statewide temperatures for September. Twenty-two additional states had statewide temperatures that ranked in the top ten highest temperatures in the 124-year period of record for the respective states. Only six states in the northwestern quadrant of the nation and in the southern Plains had statewide temperatures close to the long-term average.
  Alaska reported a statewide temperature of 44.3 degrees Fahrenheit, the third highest temperature reading for the state's period of record that commenced in 1925.
  The September 2018 average precipitation across the "Lower 48 states" was 1.00 inch above the 20th century average with a nationwide average of 3.49 inches, making it the third wettest September since 1895. Most states in the eastern half of country had statewide precipitation totals that were above- to much-above average amounts. Texas and West Virginia experienced their wettest September since 1895, while another fourteen states running from the lower Mississippi Valley northward to the Midwest and the Middle Atlantic States. However, two states east of the Mississippi Valley (Florida and Georgia) did have below average statewide precipitation in September. The western half of the nation was relatively dry in September, with Utah reporting its second driest September in 124 years, Idaho its fourth driest, followed by California (6th driest), Nevada (7th) and Wyoming (12th driest).
  Alaska experienced its third driest September on record.
  [NOAA/NCEI State of the Climate]
  NOTE: A description is provided of the climatological rankings employed by NCEI for their monthly and seasonal maps. [NOAA/NCEI]
• September national drought report -- The National Centers for Environmental Information for has posted its September 2018 drought report online. Using the Palmer Drought Severity Index, approximately 21 percent of the coterminous United States experienced severe to extreme drought conditions at the end of September, while 14 percent of the area had severely to extremely wet conditions.
• Early fall extremes found in waters surrounding Alaska -- A map of the sea surface temperature departures during the month of September 2018 from the 1981-2010 normals was plotted across the waters surrounding Alaska. This map shows above average sea surface temperatures across the Gulf of Alaska to the south of Alaska and the Bering Sea and the Chukchi Sea to the west of the state. Some of the largest temperature anomalies were nearly a plus 4 Celsius degrees in the Chukchi Sea surrounding Russia's Chukchi Peninsula. On the other hand, the waters of the Beaufort Sea off Alaska's northeastern coast were cooler than normal, with temperature departures that as much as a negative 3 Celsius degrees. In addition, the southeastern Panhandle was in a "severe drought" according to the U.S. Drought Monitor. A dome of high atmospheric pressure situated over the 49th State that extended upward through much of the troposphere created the warm and dry conditions. [NOAA Climate.gov News]
• Five more events added to 2018 national list of billion-dollar weather and climate disasters -- Last week NOAA's National Centers for Environmental Information (NCEI) issued an update to its 2018 billion-dollar weather and climate disaster list for the U.S., with the addition of five more events that have occurred during recent months with estimated costs in excess of $1 billion each. These newly-added events are: Hurricane Florence, the Western wildfires, the Southwest/Southern Plains drought, a mid-June Colorado hail storm and a mid-April southern and eastern severe weather event that included tornadoes. With these additions, the year-to-date total as of early October has reached eleven weather and climate disaster events with losses exceeding $1 billion each across the U.S, which represents the fourth highest number of such events during the first nine months of any year since NCEI began tabulations in 1980. As many as 105 fatalities have been attributed to these events so far in 2018. [NOAA NCEI]

CURRENT CLIMATE MONITORING

• QuikSCAT scatterometer has been turned off -- During the first week of October, engineers at NASA's Jet Propulsion Laboratory turned off the SeaWinds scatterometer instrument that flew on the NASA QuikSCAT spacecraft, which was launched in June 1999. The SeaWinds scatterometer measured the speed and direction of the winds over the global ocean surface for the first decade, when the spinning antenna to stop rotating, reducing its observing swath. However, with a narrower swath that was being observed, the instrument was used to calibrate newer spaceborne scatterometers for another nine years. The shutdown of the SeaWinds scatterometer was in accordance with the decommissioning plan for the satellite. [NOAA NCEI News]
• Citizen-scientists help map urban heat island in Baltimore-Washington metropolitan area -- On two of the hottest days of summer this past August, 25 citizen-scientists traveled around the streets of Baltimore, MD and Washington, DC using specially designed thermal sensors to obtain afternoon air temperature readings at numerous locations. The data they collected were plotted on a map to determine the hottest and coolest locations as part of a NOAA-funded project to map urban heat islands. They found that some neighborhoods in the two cities with paved highways and numerous buildings with little vegetation had temperatures reaching 103 degrees Fahrenheit, while those neighboring areas with large parks with trees and other vegetation had temperatures that were as much as 17 Fahrenheit degrees lower. Comparison of the generated temperature maps with corresponding satellite images of land cover is instructive. [NOAA NCEI News]
• Tornado frequency is shifting eastward from Great Plains -- A meteorology professor from Northern Illinois University and a research scientist from the National Severe Storms Laboratory have found significant decreasing trends in frequencies of both tornado reports and tornado environments over the Great Plains known traditionally as "Tornado Alley" that cover parts of Texas, Oklahoma and northeast Colorado over the last four decades, while tornado frequency has increased over sections of the Midwest and Southeast. The researchers determined the number of tornado reports across the nation to the east of the Rockies from 1979 to 2017 and used the operational weather forecasting index called the Significant Tornado Parameter (STP) to investigate regional trends in the daily frequency of tornado-environment formation over the same time interval. The number of actual tornado reports and the historical STP analysis showed the eastward uptick in tornado frequency. This eastward shift in tornado reports and environments may be caused by either natural or human-induced climate change. [Northern Illinois University Newsroom]

CLIMATE FORECASTS

• New winter and seasonal Climate Outlooks issued -- Late last week, forecasters at the NOAA Climate Prediction Center (CPC) issued their initial US Winter Climate Outlooks for the nation covering meteorological winter (in the Northern Hemisphere) that runs from December 2018 through February 2019. They foresee a good chance that nearly three-quarters of the contiguous United States, along with Alaska and Hawaii, should expect above average temperatures. The greatest likelihood of a warmer than average winter would be found in the northwestern quadrant of the "Lower 48" and across western Alaska and most of Hawaii. Above average winter temperatures were also anticipated across the Southwest and eastward across the Midwest to the Northeastern States. The southeastern quadrant of the nation was expected to have "Equal Chances" of above or below average temperatures, as the forecasters could not find a distinct signal that would suggest either above or below average conditions.
  The winter outlook also indicates that the southern tier of states, running from Arizona eastward across the southern Rockies and the Gulf Coast States and then northward into the Middle Atlantic could expect more precipitation between December and February, with the greatest certainty being centered on northern Florida and southern Georgia. On the other hand, the northern Plains and northern Rockies, together with the Great Lakes States could experience below average winter precipitation. Elsewhere across the "Lower 48", equal chances of above or below average precipitation totals were possible. Southeastern Alaska could see above average precipitation, while Hawaii could be relatively dry.
  These winter outlooks were based in part upon CPC anticipating development of a weak El Niño event before the start of meteorological winter, which would favor these conditions. An updated winter season climate output will be posted in mid-November. [NOAA News]
  A 2:40-minute video was made by the deputy director of CPC forecaster describing the features of this CPC winter outlook.
  At the same time, CPC also released its new national Three-Month (Seasonal) Climate Outlooks for November 2018 through January 2019, corresponding to the last month of the meteorological autumn season (in the Northern Hemisphere) and the first two months of meteorological winter. Specific details of the outlooks include:
  • Temperature and precipitation outlooks -- According to their temperature outlook, more than two-thirds of the 48 contiguous United States should experience a high chance of above average temperatures for the three upcoming months. The greatest probability of such an occurrence should be found across the Northwest, running from Washington and Oregon eastward to Montana and North Dakota. The outlook indicates that sections of the Mid-South and Southeast, running from eastern Texas to the Carolinas would have nearly equal chances of warmer or cooler than normal conditions for late autumn and early winter. Alaska could also have high probability of above average temperatures. No areas across the nation should experience below average temperatures.
    The CPC precipitation outlook for November through January calls for a better than even chance for below average precipitation during the next three months across the interior Northwest, centered primarily upon Montana and northern Idaho. On the other hand, the southern tier of states, extending from Arizona eastward to the Southeastern Atlantic coast and northward to the Middle Atlantic States would have the best chances of above average precipitation through next January. The Rio Grande Valley in New Mexico and Texas, along with the Gulf Coast and coastal sections of Georgia and the Carolinas would have the highest probabilities for wetter than average conditions. Southern Alaska could also have above average precipitation. The remainder of the contiguous states were given essentially equal chances of below and above average precipitation through the first half of winter 2018-19.
    A summary of the prognostic discussion of the 3-month outlook for non-technical users is available from CPC. These forecasts were based in part upon the anticipated transition of the current ENSO conditions to El Niño conditions by the start of the last month of meteorological autumn and through the upcoming winter.
    A description is also provided as how to read these 3-class, 3-month Outlook maps.
  • Seasonal Drought Outlook -- The forecasters at NOAA's Climate Prediction Center also released their US Seasonal Drought Outlook last week that would run from late-October 2018 through January 2019. Their outlook would call for the persistence of extensive drought conditions across many areas of the West, particularly across sections of the Great Basin, southern California, interior Oregon, the northern Rockies of Montana and the northern Plains of the Dakotas. Sections of the Southwest (Arizona and New Mexico) along with coastal sections of northern California, western Oregon and western Washington could see sufficient improvement in drought conditions that would result in the possible removal from drought status by the end of January 2018. Note: a Seasonal Drought Outlook Discussion is included describing the forecasters' confidence.

CLIMATE AND THE BIOSPHERE

• A changing climate could adversely affect beer drinkers -- A team of scientists from the United States, China, Britain and Mexico recently reported that increased occurrences in severe droughts and heat waves associated with anticipated changes in global climate could result in a 17 percent reduction in the supply of barley, one of the key ingredients in the brewing of beer. They predicted that that these shortages in barley due to rising global temperatures and more volatile weather could cause beer prices to double. In addition, livestock farmers who feed barley to their animals will be forced into competition with beer producers for limited supplies of the grain. The researchers based their outlook upon computer simulations using three models. One model determined how Earth's climate would change under four different greenhouse gas emissions scenarios. A second model was a crop model in which the output from the climate model was used to determine how a barley plant would fare in certain environmental conditions and areas. A third model was an economic model that predicts price changes in beer when barley supplies dwindle. One additional factor needs to be considered -- hops, another ingredient in beer, could also experience losses in quality and quantity with a changing climate. [Scientific American]

CLIMATE AND SOCIETY

• Earthweek -- Diary of the Planet [earthweek.com]

Concept of the Week: Feedback in Earth's Climate System

Consider examples of positive and negative feedback. A warming trend in climate is likely to accelerate the rate of melting of snow and ice, producing more bare ground that absorbs more solar radiation, further raising the air temperature. A cooling trend prolongs snow and ice cover in spring and summer so that less solar radiation is absorbed, more reflected to space, bringing about additional cooling. In both cases, feedback is positive because the initial change in temperature is amplified.

Consider an example of negative feedback. While feedbacks among temperature, cloud cover, and radiation are not well understood and depend upon circumstances (e.g., type and height of clouds), they could be either positive or negative. It is thought that a warming trend in climate should increase the rate of evaporation of water from Earth's surface and thereby increase low cloud cover. A thicker and more extensive low-cloud cover reflects more solar radiation to space thereby inhibiting a further rise in surface temperature. Hence, this negative feedback would dampen the initial temperature change.

Understanding feedback in the climate system is essential for modeling and predicting climate change. If some agent or mechanism alters the climate, then feedback may either amplify (positive feedback) or dampen (negative feedback) the change in climate. As demonstrated later in this course, many agents and mechanisms can bring about climate change (e.g., variations in solar energy output, regular fluctuations in Earth-Sun geometry). While these climate forcing agents and mechanisms drive climatic change, processes within the planetary climate system involving feedbacks significantly impact the magnitude of climate change.

Overall, which type of feedback prevails in Earth's climate system, positive or negative? A system in which positive feedback prevails is unstable. For Earth, this would move the climate regime toward an extreme characterized by excessive cold that would encase the planet in snow and ice ("snowball" or "ice ball" Earth) or toward the other extreme resulting in much higher temperatures--the product of a runaway greenhouse effect. Although Earth's climate has varied considerably over the billions of years that constitute geologic time, it appears likely that Earth's climate system has been nearly stable with negative feedbacks generally compensating for positive feedbacks.

Historical Events:

• 22 October 1987...Yakutat, AK surpassed their previous all-time yearly precipitation total of 190 inches. Monthly records were set in June with 17 inches, in September with 70 inches, and in October with more than 40 inches. (Sandra and TI Richard Sanders - 1987)
• 22 October 2005...Isla Mujeres, Mexico set the Northern Hemisphere's and Western Hemisphere's 24-hour rainfall record with 64.33 inches thanks to Hurricane Wilma. (National Weather Service files)
• 24 October 1951...Sacramento, CA reported a barometric pressure of 29.42 inches, to establish a record low for October. (The Weather Channel)
• 25 October 1977...Dutch Harbor in Alaska reported a barometric pressure reading of 27.31 inches (925 millibars) in a non-tropical storm to establish an all-time record for the state. (The Weather Channel)
• 26 October 1859...New York City had their earliest substantial snow of record as four inches blanketed the city. (David Ludlum)
• 26 October 1919...The temperature at Bismarck, ND plunged to ten degrees below zero, the earliest subzero reading of record for the city, and a record for the month of October. (The Weather Channel)
• 26 October 1926...Barrow, AK received a record fifteen inches of snow, and also established a 24-hour precipitation record of 1.00 inch, which lasted until the 21st of July in 1987. (The Weather Channel)
• 26 October 1993...The temperature at Eureka, CA soared to 87 degrees to set an all-time high temperature record for the city. (Intellicast)
• 26 October 2010...The lowest barometric pressure ever recorded in the U.S. between the Rockies and the Appalachians with a non-tropical system was set at Big Fork, MN, with a pressure of 955.2 millibars (28.21 inches of mercury). (National Weather Service files)
• 27 October 1929...A snowstorm dumped 27 inches upon Ishpeming, MI in 24 hours to establish a state record. (David Ludlum)
• 28 October 1936...The temperature at Layton, NJ dipped to 9 degrees above zero to establish a state record for the month of October. (The Weather Channel)
• 28 October 1991...Yakima, WA recorded 2.4 inches of snow, equaling the record for October. (Intellicast)

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Prepared by Edward J. Hopkins, Ph.D., email hopkins@aos.wisc.edu
© Copyright, 2018, The American Meteorological Society.