Why don't we get superstrong summer storms?

By Rick Thoman
Alaska Climate Specialist
Alaska Center for Climate Assessment and Preparedness
International Arctic Research Center/University of Alaska Fairbanks

During the fall and winter we regularly talk about how ocean water that is unusually warm or is open water instead of ice covered can influence the strength of storms that impact Western Alaska.
But during summer, when it's pretty much all open water and the water is quite a bit warmer than in the winter, there is much less storminess than in fall or winter.
Why is that?
The answer lies in the atmosphere. Storms at mid- and high latitudes get their energy from horizontal air temperature differences: In the northern hemisphere that typically means colder and drier air through a significant portion of the lower atmosphere to the west and northwest of the low pressure central and milder and more moist air to the east and southeast of the center.
However, during the summer there is rarely enough of a temperature difference over the Bering Sea to support strong storms. From this week's graphic, we see that July long-term average temperature near 5,000 feet above sea level (often representative of the atmosphere above the near surface effects) hardly varies over the Bering Sea.
There are more substantial differences over the Chukchi Sea north of Point Hope, and summer (July-September) is the stormiest time of year there.
November is quite different (the bottom half of the graphic), with a large north-to-south difference in temperatures across the Bering Sea: 10°F difference between Nome and Unalaska. And that's the 30-year average, which means that roughly half the time the difference would be more than 10°F. Because ocean water has to be at least 29°F (otherwise it would be sea ice) and eastern Russia land areas are regularly very cold, especially once the land becomes snow covered, it is much more common to develop strong temperature contrasts over the region, which in turn and fuel more frequent and stronger storms even though the ocean is colder and partially ice covered.