WEEKLY WEATHER AND CLIMATE NEWS

27 November-1 December 2017

Items of Interest:

• From http://www.nws.noaa.gov/om/severeweather/severewxcal.shtml
• Weather Awareness -- During this week (26 November-2 December)
  Georgia and South Carolina will observe Winter Weather Awareness Week in their respective states. Residents of these states should become aware of the hazards associated with winter storms and other cold weather events by reviewing the material prepared by the local National Weather Service Office.
• Beginning of meteorological winter season -- The winter meteorological season in the Northern Hemisphere starts on Friday (1 December). Recall that climatologists and meteorologists have elected to use a standard three-month grouping to identify each meteorological season. Hence, the months of December, January and February are considered the winter meteorological season. You will note that the winter solstice, marking the day where the length of daylight is least in the Northern Hemisphere is still three weeks away, falling on Thursday, 21 December 2017. Since the lowest temperatures typically fall in mid to late January, the meteorological winter tends to be centered on the coldest time of the year in the Northern Hemisphere.
  In addition, Thursday (30 November) marks the end of the official 2017 hurricane seasons in the North Atlantic, which includes the Gulf of Mexico and the Caribbean, along with the eastern and central North Pacific basins.
• The 2017 hurricane seasons reviewed -- With the end of the official 2017 hurricane season in both the North Atlantic and North Pacific on Thursday (30 November 2017), a quick review of this year's tropical cyclone statistics for the official 2017 hurricane season has been made for both basins. [AMS DataStreme Atmosphere]
  For those who are interested in obtaining historic hurricane information, the "Historical Hurricanes Mapping & Analysis Tool" developed by NOAA allows the search and display of detailed data for more than 6000 tropical cyclones in seven of the planet's major ocean basins based upon a data set that runs from 1842 to 2016. Coastal population trends are also available for the Atlantic and Gulf Coasts of the United States.
• High-quality maps of December temperature and precipitation normals across US available -- The PRISM Climate Group at Oregon State University's website has prepared high-resolution maps depicting the normal maximum, minimum and precipitation totals for December and other months across the 48 coterminous United States for the current 1981-2010 climate normals interval. These maps, with a 800-meter resolution, were produced using the PRISM (Parameter-elevation Regressions on Independent Slopes Model) climate mapping system.
• December weather calendar for a city near you -- The Midwestern Regional Climate Center maintains an interactive website that permits the public to produce a ready to print weather calendar for any given month of the year, such as December, at any of approximately 270 weather stations around the nation. (These stations are NOAA's ThreadEx stations.) The entries for each day of the month includes: Normal maximum temperature, normal minimum temperature, normal daily heating and cooling degree days, normal daily precipitation, record maximum temperature, record minimum temperature, and record daily precipitation; the current normals for 1981-2010.
• It's Sure Dark! -- Have you noticed that the sun is setting early these days? During the first ten days of December, many locations throughout the country will experience their earliest sunset times of the year. The exact day for the earliest sunset depends upon the latitude, so you may want to check the date in your locale from the sunrise tables appearing in an on-line, interactive service available for the entire year at most cities in the United States. The reason for the earliest sunsets occurring in early December rather than on the winter solstice (during the early morning hours of Wednesday, 21 December 2016) is that the sun is not as precise a timekeeper as our watches. Because of a combination of factors involved with Earth's elliptical orbit about the sun and the tilt of Earth's spin axis with respect to the plane of the ecliptic, the sun appears to "run fast" by as much as 15 minutes as compared with clock time in November. However, with the approach of the winter solstice and perihelion (the smallest earth-sun distance during the morning of 4 January 2017), the apparent sun slows during December and finally lags the clock by 12 minutes in February. Consequently, a noticeable and welcome trend toward later sunsets can be detected by the end of December, especially by those residents in the northern part of the country. However, the latest sunrises occur at most locales in early January, meaning that early risers will continue seeing dark and dreary mornings for another month.
• "Coldest day of the year" is on the horizon -- NOAA's National Centers for Environmental Information (NCEI) produced a set of "Coldest Day of the Year" maps for the contiguous United States, Alaska, Hawaii and Puerto Rico showing the dates of the lowest daily minimum temperatures of the year as calculated from the 1981-2010 climate normals. Many places across the West will experience their lowest daily temperatures starting during the next two to three weeks in early December. On the other hand, some areas across the West will not reach their lowest daily temperatures of the year until late January. [NOAA NCEI News]
  [Notes: (1.) According to the seasonal variations in the long-term average or "normal" temperatures, many locations across the nation not along the coasts typically have their lowest normal daily high and low temperatures during the third week of January, nearly one month after the winter solstice. However, areas across the West have their lowest temperatures during the month of December, with elevation becoming an influence.
  (2.) For comparison purposes, check the corresponding NCEI map for the "Warmest Day of the Year" that shows the dates of occurrence of the highest maximum temperatures. EJH]
• First snow of season histories are available for several thousand US weather stations -- NOAA's National Centers for Environmental Information has assembled an interactive map that allows the user to obtain the dates of the first measurable snowfall (0.1 inches or more) for several thousand weather stations across the United States (including Alaska) in the Global Historical Climatology Network that have at least 20 years of record. Clicking on a station location will provide not only the date of the first observed snowfall at that location, but the amount of this first snow and the first year of observation for that station. [NOAA Climate.gov News]
• SKYWARN™ recognition -- Next Saturday 2 December 2017 (starting at 00Z or 7:00 EST PM on Friday night) has been declared SKYWARN™ Recognition Day, a day in which the National Weather Service and the American Radio Relay League celebrate the contributions made by volunteer SKYWARN™ radio operators during the past year's Severe Weather Operations.

Weather and Climate News Items:

• Eye on the Tropics -- During the last week, a tropical cyclone developed over the southwestern Caribbean Sea in the North Atlantic basin and then after passing over Central America entered the eastern North Pacific basin near the end of week. A tropical depression formed during the predawn hours of last Monday morning over the waters of the southwestern Caribbean (a portion of the North Atlantic basin) approximately 300 miles to the east of Bluefields, Nicaragua. By early Monday afternoon, this nearly stationary tropical depression had intensified to become Tropical Storm Otto, the fifteenth named Atlantic tropical cyclone of 2016. Slightly more than 24 hours later (mid Tuesday afternoon, 22 November), Otto became the basin's seventh hurricane of the year as maximum sustained surface winds reached 75 mph as it remained roughly 300 miles off the Nicaraguan coast. By last Thursday morning Otto had intensified to become a category 2 hurricane on the Saffir-Simpson Scale before making landfall on the southern Nicaraguan coast near the town of San Juan de Nicaragua during the early afternoon. After landfall Otto weakened to a tropical storm as of mid Thursday evening. Moving westward across Nicaragua and Costa Rica, Otto produced torrential rainfall that resulted in flooding across these two countries with a loss of at least nine lives. [CNN] Early Friday morning emerged as a tropical storm from Costa Rica and out over the waters of the eastern North Pacific. According to Dr. Phil Klotzbach, Otto was the fifth named tropical cyclone on record to have crossed from the Atlantic to the eastern North Pacific. [The Weather Channel] On Saturday morning Otto was downgraded to a tropical depression as it was located nearly 700 miles to the west-southwest of Liberia, Costa Rica. The NASA Hurricane Page has additional information and satellite images on Hurricane Otto.
  In the western North Pacific basin, a tropical depression formed late last week over the Leyte Gulf just to the east of the Philippine Islands. Traveling toward the west-northwest west across the central Philippine Islands, this tropical depression intensified to become Tropical Storm Tokage. Over the past weekend Tokage curved toward the northwest and then to the north-northeast as moved out across the South China Sea. As of early Monday (local time), Tropical Storm Tokage was located approximately 230 miles to the northwest of Manila. Philippines. Forecasts indicate that Tokage would travel westward across the South China Sea before dissipating on Tuesday near the Paracel Islands.
• Australian tropical cyclone season outlook issued -- Forecasters at the Australian Government's Bureau of Meteorology recently released an outlook for the upcoming 2016-17 Australian tropical cyclone season that typically begins in November and runs through April. These forecasters foresee an above-average tropical cyclone activity in the five regions that surround that continent, with the best chances for the above-average numbers of tropical cyclones being in the Australian region in the south central section of the country (with a 67- percent chance) and the Northwestern sub-region (63-percent chance). Their outlook for a more active season is based upon a transition from ENSO-neutral to weak La Niña conditions across the tropical Pacific Ocean, together with warmer than average ocean waters located to the north and east of Australia. Typically, the waters around Australia experience more tropical cyclones during La Niña events. [Australian Bureau of Meteorology]
• Making a snow forecast for North America during a La Nina winter -- With a weak La Niña event being anticipated for this upcoming winter, a meteorologist for NOAA's Climate Prediction Center posted a guest article in which he compares snowfall patterns across North America during La Niña winters between 1950 and 2009 with average snowfall totals for that same period. He provides maps of the snowfall departures for all La Niña winters during this span, as well as for winters that are associated with both weak and strong La Niña events. These maps show that a La Niña tends to favor increased snowfall across sections of the West Coast of North America from Oregon northward to southwestern Alaska, across the Cascades and the northern Rockies, the Upper Midwest, areas downwind of the Great Lakes and across eastern Canada. On the other hand, reduced snowfall is seen across scattered areas that tend to experience snow in the Southwest, the central-southern Plains, and the Middle Atlantic States. [NOAA Climate.gov News]
• Review of October 2017 global temperatures and sea ice cover -- Preliminary data analyzed by scientists at NOAA's National Centers for Environmental Information (NCEI) indicated that the global combined land and ocean average surface temperature for the October 2017 was 1.31 Fahrenheit degrees above the 20th century average (1901-2000) for the month. Therefore, last month's global combined temperature tied the temperature for October 2003 for being the fourth highest October temperature since global temperature records began in 1880. When considered separately, the monthly average temperature over the global oceans for October 2017 was 1.13 Fahrenheit degrees above average, the fourth highest October ocean temperature in 138 years of record. The monthly average temperature of the land surface for this recently concluded month was 1.78 Fahrenheit degrees above average, which represented the eleventh highest October land surface temperature on record.
  When considering the combined land-ocean global temperature for the year to date (January-October 2017), this temperature was the third highest global temperature for the first ten months of any year since 1880. [NOAA/NCEI State of the Climate]
  A global map of Selected Significant Climate Anomalies and Events for October 2017 is available from NCEI.
  According to satellite data collected by National Snow and Ice Data Center, the sea ice over the Arctic Ocean during October 2017 was the fifth smallest areal extent for any October since satellite-derived ice records began in 1979. The sea ice around Antarctica also was the fifth smallest October ice extent in the last 39 years. [NOAA/NCEI Global Snow & Ice]
• Extent of sea ice in Alaska waters reaches record low extent this fall -- Sea ice experts have found that the extent of sea ice covering the Bering Sea to the west of Alaska and the Chukchi Sea to the northwest of the 49th State during this past fall has been the smallest since 1978 when satellite surveillance began. The lack of sea ice into late fall has profound implications not only for Alaskan marine life, but also for the native peoples that reside in coastal communities. [NOAA Climate.gov News]
• Thunderstorms studied to improve military's battlefield mission -- A scientist at the US Army Research Laboratory has discovered a pattern within the evolution of a thunderstorm cell involving downdrafts and supercooled water droplets that could be used to better predict how weather and the environment will affect Army assets such as unmanned aerial systems on the battlefield. [US Army]
• ....
• Climate changes in Europe during 19th century triggered immigration to North America -- Researchers at Germany's University of Freiburg claim that a changing climate in western Europe during the mid-19th century associated with the latter stages of the Little Ice Age appears to have been a major factor in driving the migration of many people from southwestern Germany to North America. During the early to mid-19th century, mountain glaciers re-advanced in the Alps due to cool summers and harsh winters. Other extreme weather events such as droughts and floods also helped cause low crop yields and rising cereal prices that ultimately lead to emigration. The researchers identified several waves of emigration, beginning with the "Year without a Summer" (1816) that followed the previous year's eruption of the Tambora volcano in Indonesia, and then in 1846, when an extremely hot and dry summer led to bad harvests and high food prices. However, climate may have been less of a significant factor in driving the largest emigration wave that extended from 1850 to 1855. [European Geosciences Union News]
• An All-Hazards Monitor -- This Web portal provides the user information from NOAA's National Weather Service, FAA and FEMA on current environmental events that may pose as hazards such as tropical weather, fire weather, marine weather, severe weather, drought and floods. [NOAA/NWS Daily Briefing]
• Earthweek -- Diary of the Planet [earthweek.com]