July 2023 Temperature and Precipitation
July 2023 Temperature and Precipitation
Near Record Warmth in the Arctic
This post presents the climate analysis model perspective of July 2023 temperatures and precipitation and the upper air pattern that supported this extraordinary month. July weather and climate highlights and station based temperature and precipitation departures for Alaska are here. The July 2023 wildfire and ocean temperatures/sea ice summaries are here.
Temperature
July was overall a very mild month in the Arctic, and Greenland, Northwest Canada, northern Alaska and the western Russian Arctic were especially warm relative to the 1991-2020 average (Fig. 1, left). Baffin Island (Canada), Iceland and the Scandinavian Arctic saw the largest departures on the negative side. Mid-summer temperature departures from normal are always small over the central Arctic Ocean because most of the heating goes into melting snow and sea ice and much less into warming the air. The Arctic (land and ocean areas poleward of 60N) July average temperature was 0.84°C above the 1991-2020 average, making this the second warmest July on record: only 2016 was slightly warmer (Fig. 1, right).
Zooming into Alaska and vicinity (Fig. 2), we see most of the region was warmer than normal, but especially the lower Mackenzie River valley westward into the Brooks Range and North Slope of Alaska. Southwest and parts of Southcentral Alaska were cooler than normal but not dramatically so. This was due to much above cloudiness and rainfall (see below). However, this area of slightly below normal average temperatures was larger enough to temper the warmth elsewhere, so for Alaska as a whole the July average was “only” the sixth warmest July based on the ERA5 reanalysis (2019 by far the warmest). For the Yukon Territory, this was by far the warmest July on record (ERA5 reanalysis), more than 1°C warmer than July 1989.
Precipitation
Southcentral Alaska and western Alaska from Bristol Bay to the western North Slope were generally wetter than average in July, with rainfall in parts of this area more than twice the 1991-2020 average (Fig. 3). Most areas father east were drier than average, and the eastern Gulf of Alaska coast and parts of the Northwest Territories especially dry, with generally less than half of the average July precipitation. This is an usually coherent pattern for July precipitation departures, which often shows higher small-scale variability due to the frequent showery nature of rainfall over much of the region.
In most of the region July rainfall continued the pattern from June, so the departure from normal pattern in Fig. 4 does not look too different from the July-only total. However, there are some differences, most notably in Southeast Alaska and easternmost Chukotka, where June rainfall was above a bit above normal, so the two month total, while below normal, was not extreme.
Upper Air Pattern: Driving the Weather
The mid-atmosphere flow pattern was relatively stagnant during the month, so the average explains much of climate scale patterns at the ground. Most notable is the high pressure aloft centered over the southern Yukon, which served to anchor the warm air in northwest Canada and eastern Alaska. Low pressure over the northern North Atlantic near the Faeroe Islands, the northern Laptev Sea and Bering Sea correlate well with the below normal temperature areas with the notable exception of Baffin Island.
And since folks are asking, the newly emerged El Niño was not a factor in July 2023 northern latitudes climate: it takes time for the atmosphere to respond to changes in equatorial Pacific ocean surface temperature and that was only beginning to happen in July.