WEEKLY WEATHER AND CLIMATE NEWS

25-29 May 2020

Items of Interest:

• Zenithal Sun -- Early this week (25-27 May) marks one of the two times during the year when the noontime sun is directly overhead to residents on Oahu (Honolulu metropolitan area). [timeanddate.com]
• Change in season -- Meteorological spring in the Northern Hemisphere, the three-month span from March through May, concludes next Sunday (31 May 2020), while meteorological summer (June, July and August) will commence on the following day.
• NOAA Extreme Weather Information Sheets are updated -- NOAA's National Centers for Environmental Information (NCEI) has updated the NOAA Extreme Weather Information Sheets (NEWIS) that provides emergency contact information for residents of coastal regions. These two-page reference sheets, which were first issued in 2006 after Hurricane Katrina, contain local, state, and federal phone numbers and websites in case of emergency. Currently, 22 updated NEWIS sheets are available for coastal locales from Texas to North Carolina, Hawaii, Puerto Rico, and the U.S. Virgin Islands. [NOAA NCEI News]
• Forty year partnership for satellite observing continues -- NOAA recently announced that the Cooperative Institute for Meteorological Satellite Studies (CIMSS) will continue at University of Wisconsin–Madison for the next five years, in recognition of the strength and value of the decades-long collaboration. CIMSS, which is collocated with the University's Space Science and Engineering Center (SSEC), is recognized internationally for its satellite expertise, spanning geosynchronous and polar-orbiting platforms. This network of satellites forms the backbone of a global observing system developed to monitor the planet and ensure public safety. The weather, climate and ocean sciences have all profited immensely. The current award brings as much as $150 million to CIMSS. [University of Wisconsin-Madison News] (Editor’s Note: Many of the satellite images and products associated with them that appear in this course have their origins in CIMSS and SSEC. EJH)

Weather and Climate News items:

• Eye on the tropics -- Tropical cyclones were detected over the waters of the western North Pacific, the North Indian and South Indian Oceans during the last week:
• In the North Indian Ocean basin, Tropical Cyclone Amphan was tracking to the north-northwest across the Bay of Bengal as a category 4 tropical cyclone (on the Saffir-Simpson Scale) at the start of last week. At the time, the center of Amphan was located approximately 675 miles to the south-southwest of Kolkata, India (formerly known as Calcutta). During the course of last Monday, Amphan strengthened to become a category 5 tropical cyclone as maximum sustained surface winds peaked at 165 mph. Traveling toward the north-northeast, Tropical Cyclone Amphan made landfall approximately 150 miles west of Kolkata as a category 2 tropical cyclone with sustained winds of 100 mph. A storm surge, which had been generated by the 160-mph winds, reached heights of 17 feet as it approached the coast. Torrential rains accompanying Amphan also spread across densely populated sections of eastern India and Bangladesh. More than 2.6 million people fled the region, but evacuation during the pandemic brought additional dangers, as more than 80 people were killed and thousands left without power. [BBC News] Amphan weakened quickly after making landfall, with the remnants of this tropical cyclone heading toward the south-facing slopes of the Himalayan Mountains, resulting in upslope rains. Consult the NASA Hurricane Blog for additional information and satellite imagery on Tropical Cyclone Amphan.
• In North Atlantic basin, Tropical Storm Arthur was continuing traveling toward the north-northeast off the coast of South Carolina at the start of last week. As the first named Atlantic tropical cyclone of 2020, this system strengthened slightly as it approached the North Carolina coast by late Monday morning. At that time, maximum sustained surface wind speeds had reached 50 mph as the center of Arthur approached to within 20 miles of Cape Hatteras, NC. By Monday afternoon, Tropical Storm Arthur began taking a track toward the east-northeast, moving away from North Carolina's Outer Banks. Coastal North Carolina was buffeted with strong winds and torrential rains that produced between 3 to 5 inches of rainfall at some locations. Ocean swells generated by Arthur were affecting portions of the mid-Atlantic and Southeast coasts of the U.S. By early Tuesday morning, sustained surface winds had reached 60 mph as the center of the storm was approximately 300 miles to the east-northeast of Cape Hatteras. Arthur became a post-tropical cyclone late Monday morning as it was approximately 400 miles to the east-northeast of Cape Hatteras, or 380 miles to the northwest of Bermuda. However, maximum sustained wind speeds associated with this remnant low remained at 60 mph. Additional information and satellite images on Tropical Storm Arthur can be found on the NASA Hurricane Blog.
  
• In South Indian Ocean basin, a tropical low pressure system formed last Wednesday nearly 500 miles to the southwest of Padang in Sumatra. Tracking to the south-southeast, this low strengthened into a tropical storm that was assigned the name Mangga. On Friday, Tropical Storm Mangga passed to the west-northwest of the Cocos Islands. Over the next day, Mangga traveled toward the southeast as a minimal tropical storm, with maximum sustained surface winds remaining at 40 mph. By early Sunday, Mangga had become an extratropical storm, well before reaching the western coast of Australia. The NASA Hurricane Blog has additional information on Mangga.
• Connection seen between increasing global temperature and hurricane intensity -- Scientists at NOAA's National Centers for Environmental Information and the University of Wisconsin-Madison's Cooperative Institute for Meteorological Satellite Studies analyzed hurricane satellite imagery from 1979 through 2017. The analysis techniques employed provided a more uniform dataset that could be used to detect statistically significant trends. Their research substantiates the connection between warming trends on Earth and increases in hurricane intensity. In nearly every ocean basin where tropical cyclones of hurricane-strength form, the maximum sustained winds are getting stronger. [NOAA NCEI News]
• An atmospheric teleconnection seen between U.S. and tropics -- Researchers at the University of Miami's Rosenstiel School of Marine and Atmospheric Science recently reported finding a new connection between tropical weather events and U.S. rainfall during El Niño years. The researchers analyzed 39-years of weather data from the National Centers for Environmental Prediction to understand how the Madden-Julian Oscillation (MJO) leads to pressure and rainfall anomalies over the North Pacific and North America. The MJO is a phenomenon of sub-seasonal atmospheric variability in the tropical Indo-Pacific Oceans. When both an El Niño Southern Oscillation (ENSO) and MJO event are occurring simultaneously, the rainfall pattern across the U.S. typically seen from ENSO can be considerably altered for a few days to weeks due to interference from the MJO. This study could help better predict rainfall during an El Niño event. [University of Miami Rosenstiel School of Marine and Atmospheric Science News]
• An updated look at U.S. record hailstones and hailstorms -- Christopher Burt, a noted weather historian, has posted a blog on Weather Underground entitled "U.S. Hailstone and Hailstorm Records" that contains an updated listing of the largest hailstones that have been collected (and measured) across the U.S. The costliest and deadliest hailstorms in U.S. history are also listed. He also provides a U.S. hailstorm climatology that contains maps of the contiguous U.S. showing the geographic distribution of the number of total hail reports and total large (2-inch or greater diameter) hail reports from 1955 to 2002. The topic of how the hail climatology could be affected by climate change is also addressed. [Weather Underground Category 6™]
• Global temperatures and ice for April 2020 reviewed -- Using preliminary data collected from the global network of surface weather stations, scientists at NOAA's National Centers for Environmental Information (NCEI) report that the combined global land and ocean surface temperature for April 2020 was the second highest for any April since comprehensive global climate records began in 1880; this April 2020 temperature anomaly (or departure from average) was 1.91 Fahrenheit degrees above the 20th-century (1901-2000) average. The largest positive global ocean-land temperature departure for any April in the 1880-2020 record was set four years ago (April 2016 had a positive 2.03-Fahrenheit degree departure).
  The scientists also reported that when considered separately, the April 2020 average temperature anomaly over the oceans was 1.49 Fahrenheit degrees above the 20th-century average making this last month the highest April global ocean temperature departure in the 141-year record. The month's average temperature over the land surfaces was 2.99 Fahrenheit degrees above the long-term average, which was the secomd highest April land temperature departure on record.
  According to data from the Rutgers Global Snow Lab, the Northern Hemisphere snow cover extent for April 2020 was the thirteen smallest in the 54-year period of record.
  According to the National Snow & Ice Data Center, April sea ice extent data for the Arctic Ocean in 2020 was the fourth smallest extent in April extent since satellite records began in 1979. The previous smallest April Arctic sea ice extent on record occurred during April of 2016 and 2017. The extent of sea ice on waters around Antarctica in April 2020 was the seventh smallest in the satellite era.
  A global map of "Selected Significant Climate Anomalies and Events for April 2020" is available from NCEI.
  [NOAA/NCEI State of the Climate] or [NOAA Climate.gov]
• Official Atlantic and Pacific hurricane outlooks issued for 2020 -- During the last week, scientists with NOAA's Climate Prediction Center (CPC) released their outlook for the upcoming 2020 hurricane seasons in the North Atlantic basin, which includes the Caribbean Sea and the Gulf of Mexico, the eastern North Pacific basin, which lies between the western coast of North America and the 140-degree West meridian of longitude, and the central North Pacific basin, which is situated between the 140-degree West meridian and the International Dateline.
• Their outlook for the North Atlantic basin indicates a 60-percent chance of an above-normal season, a 30-percent chance of a near-normal season, and a 10-percent chance of a below-normal season in 2020. The forecasters predict a 70-percent likelihood of 13 to 19 named tropical cyclones (hurricanes and tropical storms with sustained surface winds of at least 39 mph), including six to ten of these tropical cyclones becoming hurricanes (maximum sustained surface winds of 74 mph or higher). Between three and six of these hurricanes could become major hurricanes (Category 3 hurricanes or greater on the Saffir-Simpson Hurricane Intensity Scale, with maximum sustained surface winds of 111 mph or higher). The forecasted numbers include Tropical Storm Arthur, a pre-season system that formed off the Florida coast one week ago. (Based upon long-term statistics, an average Atlantic season consists of 12 named tropical cyclones per year and the six hurricanes that normally form during each year. Three of these hurricanes typically become major hurricanes.) The forecasters based their above-normal forecast upon four factors: i.) anticipated continuation of ENSO-neutral conditions, with the possible transition to La Niña conditions, which would not suppress hurricane activity; ii.) Above-average sea surface temperatures (SST), reduced vertical wind shear and weaker trade winds in the tropical Atlantic basin that favor increased activity; iii.) an enhanced west African monsoon that favors increased tropical cyclone activity; and iv.) an ongoing high-activity era that began around 1995.
  NOAA will update their 2019 Atlantic hurricane outlook in early August, just before the peak in the season. [NOAA News]
  For comparison, hurricane expert Phil Klotzbach and colleagues at Colorado State University had released a forecast of the 2020 Atlantic hurricane season in early April that called for a season with above-average tropical cyclone activity. They envisioned sixteen named tropical cyclones, which include eight hurricanes. Of these hurricanes, the forecasters foresee four major hurricanes. [The Tropical Meteorology Project]
• The CPC outlook for the eastern North Pacific basin in 2020 calls for a near or below-average season, with a 40-percent chance of a near-normal season and a 30-percent chance of a below-normal season and a 25-percent chance of an above-normal season. A 70-percent probability is given for the development of 11 to 18 named storms, of which 5 to 10 are expected to become hurricanes, including one to four major hurricanes. On average, slightly more than 15 named tropical cyclones develop annually over the eastern Pacific, with slightly more than eight hurricanes developing per annum. The long-term average of major hurricanes is slightly more than four in a year. The forecasters feel that a near or below-average season is likely because of the below- or near-average sea surface temperatures (SSTs) across the eastern Pacific hurricane region, while waters are warm in the Atlantic. Furthermore, ENSO-neutral conditions are anticipated to continue into autumn, with even the possible transition into a La Niña condition. [NOAA CPC]
• The CPC outlook for the central North Pacific basin suggests a near or below average season, with a 40-percent chance of a near-normal season, a 30-percent chance of a below-normal season and a 25-percent chance of an above-normal season. Their outlook calls for possible formation of two to six tropical cyclones (which includes tropical depressions, tropical storms, and hurricanes), as compared with the long-term average of four to five tropical cyclones. The indication of a below-average season is based upon the anticipated continuation of ENSO-neutral conditions during the hurricane season, and near to below-average ocean temperatures in the main hurricane formation region. [NOAA News]
• A single graphic entitled "NOAA's 2020 Hurricane Season Outlooks" summaries the outlooks for all three basins.
• New Seasonal (3-month) Climate Outlooks for this summer issued -- Near the end of last week, forecasters at the NOAA Climate Prediction Center (CPC) released their new national Three-Month (Seasonal) Climate Outlooks for the upcoming summer season. These three months, running from June through August 2020, are identified as meteorological summer for the Northern Hemisphere. Specific details of their outlooks include:
  • Temperature and precipitation outlooks -- According to their temperature outlook, approximately 80 percent of the contiguous states should experience high chances of above average temperatures for these three upcoming months. The highest probability of a warmer than average summer would be centered over the Southwest, across New England and south Florida. In the West, the Four Corner States of Arizona, Colorado, New Mexico and Utah would have the highest probability of warm conditions, while other areas across the Rio Grande Valley, the Great Basin, interior sections of the Northwest also have high probabilites of warm conditions. In the East, most of New England and adjacent areas of Upstate New York have a high probabilty of a warm summer. The remains 20 percent of the land area of the contiguous U.S., across the Missouri and upper Mississippi Valleys would be expected to have nearly equal chances of warmer or cooler than normal conditions. The outlook for Alaska indicates that the entire 49th State would have a high chance of having a summer with above average temperatures.
    Their precipitation outlook calls for better than even chances of wet conditions for summer 2020 across nearly all of the eastern half of the contiguous U.S. The region of highest probability for a wet summer would stretch from southern Minnesota southward to the mouth of the Mississippi River and eastward across the Southeastern States to the Atlantic Coast to the south of the Del-Mar-Va Peninsula. Conversely, the northwestern quadrant of the "Lower 48" states should have good chances for below average summer precipitation, centered especially across interior sections of Washington, Oregon, northern Idaho and western Montana. The rest of the contiguous states should have equal chances of below and above average summer precipitation. These regions are found along the Southwest, the western high Plains and the Northeast. The western half of Alaska was expected to have a good chance of a wetter than average summer, while eastern sections of the state that include the Panhandle would have "equal chances" of above or below average precipitation.
    A summary of the prognostic discussion of the outlook for non-technical users is available from CPC. These forecasts were based in part on the possibility that ENSO-neutral conditions found across the tropical Pacific in May should continue through summer, with a possible formation of La Niña conditions by autumn. Furthermore, positive soil moisture anomalies for sections of the central sections of the nation were considered to be factors.
  • Seasonal Drought Outlook released -- The forecasters at NOAA's Climate Prediction Center also released their US Seasonal Drought Outlook last week that would run from mid-May through August 2020. Their outlook shows that a wide section of the West currently experiencing moderate to severe drought should continue to have drought conditions through this summer; comparison is invited with this week's United States Drought Monitor. Areas extending from the Four Corners region westward to the northern California coast and northward into the interior Northwest could also see expansion of the areal extent. However, sections of the central high Plains in Kansas and Oklahoma under moderate and severe drought conditions at the present time could see improvement in the drought, with some of the region seeing elimination of the drought by end of summer. Areas with drought along the Gulf Coast should also see elimination of the drought within the next three months. Note: a Seasonal Drought Outlook Discussion is included describing the forecasters' confidence.
• 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]