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Warm Oceans, Displaced Polar Air: Why the Eastern U.S. is Likely to See Very Severe Rainfall During May

During recent years, warm ocean surfaces have loaded up the atmosphere with increasing levels of moisture. This moisture, in turn, has fueled more powerful rain storm events across the globe. Meanwhile, climate change is generating regions of increased instability by placing much warmer than normal air masses in confrontation with cold air displaced from a warming Arctic Ocean region.

(How climate change is impacting severe weather potentials across the U.S. East Coast during May. Data provided by Earth Nullschool, Climate Reanalyzer, and the National Weather Service.)

During the coming days, this kind of pattern will generate the potential for severe rainfall events across the U.S. East Coast. NOAA is predicting that between 3-7 inches of rain is likely to fall over the next 5-7 days. But due to the unusual situation, locally extreme and unexpected events may occur.

This severe weather potential has been fed by a combination of factors. A warmer than normal Arctic Ocean has shoved cold polar air south over the Hudson Bay region. The resulting trough is generating stormy conditions and atmospheric instability over much of Eastern North America. To the south and east, much warmer than normal sea surfaces have loaded up the atmosphere with extremely high moisture levels.

(NOAA shows that heavy rainfall is likely to dominate large portions of the Eastern U.S. over the coming weeks. With a number of climate change related influences at play, the potential for outsized severe weather events exists. Image source: NOAA.)

It’s the kind of pattern — within a highly charged atmosphere — that is capable of producing serious instances of severe weather. Heavy rainfall, hail, lightning and tornadoes are all more likely. Factors associated with climate change contributing to the situation include — much warmer than normal ocean surfaces off the U.S. Eastern Seaboard and Gulf Coast, a much warmer than normal Arctic Ocean region for this time of year, displaced polar air near Hudson Bay, and warmer than normal temperatures over much of the U.S.

As Greenland melt comes more into play, and as temperatures continue to spike higher over the Arctic Ocean in coming years, we can expect to see similar patterns producing greater instability and more intense storms. Particularly for the land zones near the North Atlantic. And so what we are seeing now is a likely prelude of events to come as the Earth continues to warm coordinate with continued fossil fuel burning — with mitigating factors primarily involving reduced carbon emissions.

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