Spring 2020

Weather and Climate Review: Spring 2020

By Dr. Sean Birkel, Maine State Climatologist

Statewide Overview
Notable Weather and Climate Events
Looking Farther Afield

Statewide Overview

The Maine statewide climatological spring (March-May [MAM]) 2020 average temperature was 39.6 °F, or 72^nd percentile for the 125-year record period beginning 1895 (Fig. 1). This temperature is 2.4 °F warmer than that observed for the same period in 2019, and 1.4 °F above the 1901-2000 historical mean. The observed MAM total precipitation was 9.4 inches, or 44^th percentile for the record period (Fig. 2). This precipitation amount is 2.6 inches less than that observed in 2019, and 0.7 inches above the 1901-2000 historical mean, or near normal. In total for MAM 2020, there were 40 high and 33 low daily temperature, 32 high precipitation, and 42 high snowfall records either broken or tied statewide (data from NOAA Daily Weather Records).

: Figure 1. Statewide MAM average temperature anomaly (1901-2000 baseline) timeseries and maps. Timeseries data from the NOAA U.S. Climate Divisional Database. Spatial data from the PRISM Climate Group. These charts are also available on the Maine Climate Office website.

: Figure 2. Statewide MAM total precipitation anomaly (1901-2000 baseline) timeseries and maps. Timeseries data from the NOAA U.S. Climate Divisional Database. Spatial data from the PRISM Climate Group. These charts are also available on the Maine Climate Office website.

On the three-month average, spring 2020 was warmer than the 20^th century baseline and had near normal precipitation. The season and individual month statistics are shown in Table 1.

Table 1. Statewide MAM 2020 season and monthly temperature and precipitation statistics. “Anom” refers to anomaly, or the departure from the 1901-2000 historical mean. Data are from the NOAA U.S. Climate Divisional Database.
	Temp / Anom (°F)	Percentile	Precip / Anom (in)	Percentile
MAM	39.6 / +1.4	72^nd	9.4 / -0.7	44^th
Mar	29.7 / +3.8	77^th	2.7 / -0.6	32^nd
Apr	37.9 / -0.4	40^th	4.1 / +0.8	75^th
May	51.4 / +0.9	63^rd	2.5 / -0.9	32^nd

Notable Weather and Climate Events

March: Unseasonably warm, especially across the coastal climate division and much of the central climate division where snow melted to expose bare ground by mid-month. March will also be remembered as the month the world changed, as on the 11^th the World Health Organization declared COVID-19 a pandemic.

April-May: After a warm first week in April, unseasonably cold temperatures developed mid-month in association with a cool wave across the U.S. and southern Canada (Fig. 3). The change in weather pattern was accompanied by a powerful spring snowstorm on April 9-10 that dropped more than 10” of heavy, wet snow in some areas of coastal and central Maine, knocking out electricity to over 250,000 homes and businesses. Late season snowstorms also occurred April 21-22, and May 9 and 12 (Fig. 4) (also see snowfall total maps for the winter 2019/20 season produced by NWS-Caribou). In mid-May, the weather pattern changed from cool/wet to warm/dry, with the latter persisting into early summer.

Figure 3. Map of temperature anomalies with schematic depiction of jetstream across North America averaged for the five-day period April 15-19. The temperature anomalies are in reference to a 1979-2000 climate baseline. Source data from NCEP Climate Forecast System and Reanalysis. Temperature anomaly and other maps of historical daily mean weather are available on Climate Reanalyzer.

Figure 4. Maps of 24-hour snow precipitation for the late-season snowstorms on April 22nd and May 10th, 2020. Images from the National Snow Analysis operated through the NOAA Office of Water Prediction and NWS National Operational Hydrologic Remote Sensing Center.

Looking Farther Afield

Global Temperature: The MAM 2020 global average near-surface temperature ranks second warmest on record since widespread observations became available in 1880 (Fig. 5).

Figure 5. Global mean MAM temperature anomaly timeseries. Image from NOAA/NCEI Climate at a Glance.

As with DJF 2020, the MAM global temperature is surprisingly high given the absence of a strong El Niño. However, the exceptionally strong positive phase of the Arctic Oscillation (AO) that developed early in the year persisted through March and into April, and restricted cold air mostly over Canada while temperatures soared to record highs across Siberia (Fig. 6).

Figure 6. Map showing MAM 2019 worldwide temperature anomalies in reference to a 1979-2000 climate baseline. Source data from the European Centre Reanalysis version 5 (ERA5). Image generated using Climate Reanalyzer.

Northern Hemisphere Sea Ice: The winter 2020 maximum sea ice areal extent in the Northern Hemisphere was reached 5 March, ranking 11^th lowest for that day of year in the 1979-present satellite observation record (Fig. 7). By 31 May, the areal extent ranked 3^rd lowest, tied with that of 2018, behind only 2019 and 2016. Much of the excess melting during this interval can be linked to warm airflow into the Arctic Basin via Siberia, associated with the aforementioned months-long heatwave.

Figure 7. (Top) Timeseries of daily sea-ice extent (> 15% ice coverage at each gridcell) across the Northern Hemisphere from March 1st to June 15th as measured by satellites since 1979. (bottom) Maps of late spring sea-ice extent May 31st 1979 and 2020. Timeseries source is the NOAA/NSIDC Sea Ice Index. Maps from the NCEP Climate Forecast System and Reanalysis. Daily sea-ice extent timeseries and concentration maps are available on Climate Reanalyzer.

Tools for accessing Maine historical climate data and current weather forecasts are available on the Maine Climate Office website. For U.S. and global visualizations, visit Climate Reanalyzer. The Maine Climate Office and Climate Reanalyzer are developed and maintained by Dr. Sean Birkel with supported from the Climate Change Institute at the University of Maine.