From Cliff Mass Weather Blog
cliff mass
In the past three days, I have received several calls from friends in the media asking the same question:
Will storms like this week's “bomb” cyclone become stronger or more frequent due to global warming?
If not, could global warming lead to such growth in the future?
The answer to these questions is clear: no.
There is compelling scientific evidence that such storms are not increasing in our region and that a warming planet will not bring more weather “bombs” to our region.
First some terminology
one mid-latitude (or extratropical) cyclones It is a low-pressure center in the Northern Hemisphere around which winds rotate counterclockwise. The strength of a cyclone is usually quantified by center pressure, although size is also important. Generally speaking, the lower the central air pressure, the stronger the cyclone and the stronger the wind.
As shown below, cyclones often form in areas with strong horizontal temperature variations…in fact, this temperature difference is what fuels these storms.
Regarding central air pressure, the average storm pressure in our area is about 990-1000 hPa. The pressure may be 980-990 hPa for severe storms, 965-980 hPa for severe cyclones, and even lower for extreme storms.
Tuesday's storm dropped to a staggering 943 hPa, tying a record set over the past 70 years.
A cyclone that accelerates extremely quickly is called “bomb”…The media must have fallen in love with this term. By definition, bomb cyclones deepen by 24 hPa or more in 24 hours. This definition is completely arbitrary. Really just for fun.
Are local cyclones getting stronger?
The answer is obviously no. There is no increase in the frequency or intensity of landfills or nearshore cyclones in our region.
Most notable local cyclones occurred in the early to mid-20th century, with the last major landfalling cyclone occurring in 2006 (the Hanukkah Eve storm).
Another way to demonstrate that storms are not increasing is to plot sea level pressure over time at a point along the Washington coast (Ocean Shores). As shown below, there is no evidence of an increase in minimum pressure (e.g. below 980 hPa).
Will global warming worsen severe storms in the region?
A group of ours at the University of Washington (in collaboration with the UW Climate Impacts Group) conducted a formal study of this issue, funded by Seattle City Lights.
We draw on the best available scientific regional climate models driven by an ensemble of global climate models.
this research No An increase in extreme winds was found in the area (we checked several locations). The graph below shows an analysis of extreme wind trends at the end of the century.
There are good scientific reasons to expect little change in the intensity of midlatitude cyclones in our region.
For example, global warming preferentially warms the lower atmosphere in the Arctic, weakening the north-south temperature differences that trigger storms. On the other hand, temperature changes aloft intensify, causing storm washouts.
In summary, natural changes and processes can sometimes combine to produce very strong cyclones, like the one we experienced on Tuesday.
We have experienced a rare extreme event, and there is no reason to expect these types of storms to become more frequent as the Earth slowly warms.
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