Note: This Synoptic Discussion describes recent weather events and climate anomalies in relation to the phenomena that cause the weather. These phenomena include the jet stream, fronts and low pressure systems that bring precipitation, high pressure systems that bring dry weather, and the mechanisms which control these features — such as El Niño, La Niña, and other oceanic and atmospheric drivers (PNA, NAO, AO, and others). The report may contain more technical language than other components of the State of the Climate series.


Summary


The strong El Niño continued during March 2016 and contributed to a stronger-than-normal Aleutian Low which energized the upper-level circulation pattern over the contiguous United States (CONUS). An onshore flow and northerly storm track brought above-normal precipitation to Northern California and the northern states, contracting drought, while a slow-moving cutoff low funneled flooding precipitation into the Lower Mississippi Valley and Southern Plains. The wetter fronts and low pressure systems missed the Southwest, Central to Northern Plains, and Southeast to southern New England, resulting in below-normal precipitation and expanding areas of abnormal dryness and moderate drought. The contracted jet stream resulted in warmer than normal temperatures for most of the country and a below-average number of tornadoes. The upper-level circulation, temperature, and precipitation anomaly patterns suggest that the weather and climate of March 2016 were largely the result of atmospheric drivers originating over the Atlantic and Arctic Oceans, but also to some degree from the Pacific Ocean. See below for details.


Synoptic Discussion


Animation of daily upper-level circulation for the month
Animation of daily upper-level circulation for the month.
 Animation of daily surface fronts and pressure systems for the month
Animation of daily surface fronts and pressure systems for the month.

In the Northern Hemisphere, March marks the beginning of climatological spring which is the time of year when solar heating increases with the rising sun angle, arctic air masses are not as cold, and a contracting circumpolar vortex forces the jet stream northward. Polar air masses influence the weather over the contiguous U.S. (CONUS) less, and the warm, dry subtropical high pressure belts influence the weather more.

March 2016 followed this seasonal script — for the most part. A wild card was the strong El Niño which energized the atmosphere and produced a stronger-than-normal Aleutian Low. The Aleutian Low fed an atmospheric circulation that was very active with several upper-level troughs and low pressure systems which moved across the CONUS. The strong Aleutian Low also contributed to a warm southerly flow over Alaska which resulted in another warmer-than-normal month, wetter-than-normal conditions for some southern coastal locations, and drier-than-normal conditions for much of the rest of the state. At the surface, this circulation pattern pushed a stream of Pacific weather systems into western North America. Above-normal precipitation fell across Northern California to the Pacific Northwest and Northern Rockies, increasing mountain snowpackand improving drought conditions. However, the North Pacific subtropical high pressure center was also active this month and reinforced an upper-level ridge just off the coast of Southern California. This ridge deflected storms away from drought-stricken Southern California and the southwestern U.S., resulting in a much drier-than-normal month which expanded areas of abnormal dryness and moderate drought. By the time the Pacific weather systems crossed the Rockies, they had lost most of their moisture. This resulted in the drier-than-normal area extended from the Southwest into the Central and Northern Plains. Fronts that passed through the Central to Southern Plains brought wind but little rain. With warm temperatures and low humidity, this contributed to numerous large wildfires, especially over Oklahoma, which continued from last month.


Upper-level circulation showing cutoff low over Mexico March 10

Some of the low pressure systems moving in the jet stream flow skirted the edge of the North Pacific High and moved into the southern CONUS. One such system plunged deep into Mexico and formed a cutoff low. The cutoff low funneled huge amounts of Gulf of Mexico moisture into the Southern Plains and Lower Mississippi Valley. Over a period of three days (March 9, 10, 11), this circulation pattern combined with a complex surface frontal system to generate persistent heavy rains and widespread flooding.

Most of the air masses moving in the jet stream flow originated over the Pacific, but some of them were drawn down from Canada. The Canadian air masses were cold enough to cause the precipitation to fall as snow instead of rain. The month began with about 18 percent of the CONUS snow-covered. As below-freezing Canadian air was entrained behind each low pressure system, the snow cover expanded, reaching a peak of about 25 percent of the CONUS on the 4th and 24th. But temperatures are warming this time of year, and warm southerly winds between the snowstorms rapidly melted the snow cover, which reached a minimum of about 8 percent in the middle of the month. March ended with about 14 percent of the CONUS snow-covered.

The Bermuda High (also known as the North Atlantic High) was stronger than normal this month and influenced the weather over the western North Atlantic and eastern CONUS. It weakened low pressure systems and fronts as they moved across the Southeast to southern New England, reducing their precipitation and contributing to a drier-than-normal month. By the end of the month, several large wildfires had developed in and around the Southern Appalachians. With the North Pacific High to the west and Bermuda High to the east, severe weather was funneled in between them, mainly from the Southern Plains to Ohio Valley. There were 67 tornadoes nationwide during March (according to preliminary reports), which is below the March average of 80.

The seasonally contracting jet stream, ridges migrating in the jet stream flow, and dominance of the Bermuda High combined to enable warmer-than-normal air to dominate the CONUS. By month's end, there were 5,956 record warm daily high (2,484) and low (3,472) temperature records, which is about 22 times the 266 record cold daily high (154) and low (112) temperature records, with the CONUS ranking fourth warmest nationally for March. The REDTI (Residential Energy Demand Temperature Index) for March 2016 ranked fifth lowest in the 1895-2016 record for March, illustrating how the unusually warm temperatures in the major metropolitan areas across the country reduced heating demands.

Nationally, March 2016 ranked as the 26th wettest March on record. The wet conditions in Northern California to the Northern Rockies helped contract drought in those parts of the West. But the drier-than-normal conditions from the Southwest to Northern Plains expanded drought in those areas. Overall, the national moderate-to-exceptional drought footprint grew slightly to 12.8 percent of the U.S. as a whole, and 15.1 percent of the CONUS.

The Climate Extremes Index (CEI) aggregates temperature and precipitation extremes across space and time. Several parts of the U.S. experienced March extremes which were manifested in top-ten ranks for warm maximum and minimum temperatures. Only one region (East North Central region) ranked in the top ten category for the regional CEI. With the sixth highest warm minimum temperature component, ninth highest warm maximum temperature component, eighth highest wet spell component, and 15th highest days with precipitation component, the East North Central region had the fourth highest regional CEI. When aggregated across the nation, March 2016 had the seventh most extreme national March CEI on record, with the third most extreme warm minimum and fourth most extreme warm maximum temperature components and 19th most extreme 1-day precipitation component contributing.

North America monthly upper-level circulation pattern and anomalies
North America monthly upper-level circulation pattern and anomalies.

As the troughs and ridges migrated through the jet stream flow across North America, and the North Pacific and North Atlantic Highs exerted their influence, the circulation pattern favored ridging over the Southwest and eastern CONUS. A below-normal 500-mb height anomaly pattern prevailed across much of the North Pacific and extended into the northwestern CONUS.

Map of monthly precipitation anomalies
Map of monthly precipitation anomalies.

March 2016 was drier than normal across the Southwest to Central and Northern Plains, Southeast to southern New England, most of Hawaii, and parts of Alaska and Puerto Rico. It was wetter than normal from Northern California to the Pacific Northwest, the Northern Rockies, Lower Mississippi Valley, Great Lakes, and parts of the Southern Plains, Alaska, and Puerto Rico.

Map of monthly temperature anomalies
Map of monthly temperature anomalies.

March 2016 was warmer than normal across Alaska and the CONUS.

Northern Hemisphere monthly upper-level circulation pattern and anomalies
Northern Hemisphere monthly upper-level circulation pattern and anomalies.
Global Linkages: The upper-level (500-mb) circulation anomaly pattern over North America was part of a long-wave pattern that stretched across the Northern Hemisphere. The circulation pattern was complicated this month. At the mid- and higher latitudes, the circulation pattern consisted of a series of ridges and longwave troughs and ridges. These usually form pairs or couplets in an east-west orientation, but this month their orientation was more north-south and scattered. Troughs with below-normal 500-mb heights occurred over the North Pacific, eastern Canada, western Mediterranean/western Europe, and western Russia. Ridges with above-normal 500-mb heights occurred over western Canada (coupled with the North Pacific trough), eastern CONUS/western North Atlantic (coupled with the eastern Canada trough), Scandinavia/northern North Atlantic (coupled with the Western Europe trough), and Arctic Ocean (coupled with the western Russia trough). Beyond the Northern Hemisphere, above-normal heights extended across the Tropics to Southern Hemisphere mid-latitudes, while below-normal heights covered the Antarctic. The below-normal 500-mb heights were associated with upper-level troughing and near- to below-normal surface temperatures over western Europe and northwestern Africa, below-normal sea surface temperatures over the north central North Pacific and northwestern North Atlantic, and above-normal precipitation over Western Europe. The above-normal 500-mb heights were associated with upper-level ridging at the mid-latitudes, below-normal snow cover over the CONUS and southern and eastern Asia, above-normal sea surface temperatures in most oceans, and above-normal surface temperatures over most continents. With most of the continents having warmer-than-normal temperatures, and large portions of the equatorial Pacific Ocean (due to El Niño), Indian Ocean, Atlantic Ocean, and eastern North Pacific Ocean having warmer-than-normal sea surface temperatures, the March 2016 global temperature was well above normal.


Atmospheric Drivers


Subtropical highs, and fronts and low pressure systems moving in the mid-latitude storm track flow, are influenced by the broadscale atmospheric circulation. The circulation of the atmosphere can be analyzed and categorized into specific patterns. The Tropics, especially the equatorial Pacific Ocean, provides abundant heat energy which largely drives the world's atmospheric and oceanic circulation. The following describes several of these modes or patterns of the atmospheric circulation, their drivers, the temperature and precipitation patterns (or teleconnections) associated with them, and their index values this month:


Examination of the available circulation indices and their teleconnection patterns, and comparison to observed March 2016 temperature, precipitation, and circulation anomaly patterns, suggest that the weather over the CONUS in March reflected influences from Atlantic and Arctic atmospheric drivers with some possible influence from the Pacific drivers. The El Niño was pumping energy and moisture from the tropical Pacific into the mid-latitudes, priming the atmosphere for action. This energy was reflected in an intense Aleutian Low over the north central North Pacific. This contributed to an active jet stream and numerous Pacific weather systems. These weather systems and their storm tracks gave above-normal precipitation to some parts of the CONUS that normally expect it during an El Niño and active MJO. But the March 2016 temperature anomaly pattern did not agree with those expected with an El Niño and active MJO, which indicates that these two drivers were not the primary drivers. The temperature anomaly pattern had more in common with those expected with the AO and NAO. The WP and EP-NP indices were very weak (near zero), and the PNA teleconnections showed little similarity to the observed patterns, so these Pacific drivers likely had little influence on March's weather. But the upper-level circulation anomaly pattern agreed with the WP pattern where teleconnections exist, suggesting that there was some influence. The NAO teleconnection pattern agreed most closely with the observed upper-level circulation anomaly pattern, with the AO also showing some agreement. In summary, the temperature and upper-level circulation patterns show the best agreement with the AO and NAO, while the Pacific drivers (WP, MJO, and El Niño) showed some agreement for precipitation and (for WP) upper-level circulation.

This month illustrates how the weather and climate anomaly patterns can reflect the combined influence of atmospheric drivers (or modes of atmospheric variability) from several regions — primarily the Atlantic and Arctic, but also the Pacific.

Citing This Report

NOAA National Centers for Environmental Information, Monthly Synoptic Discussion for March 2016, published online April 2016, retrieved on April 28, 2024 from https://www.ncei.noaa.gov/access/monitoring/monthly-report/synoptic/201603.