Weather Blog

Wow! That's a low pressure!

Wow! That's a low pressure!

It's sometimes amusing to run the forecast models out a while and see what they say -- sort of like slowly unwrapping a surprise gift, you never know what will be revealed.

Monday night's model run revealed something interesting for Halloween Sunday -- a really deep low pressure center out in the Gulf of Alaska:

How deep? Try 948 mb, or 27.99" of mercury -- not to far from what would be a Category 4 hurricane if it were in fact a hurricane (which it is not, since it is not a tropical storm.)

If you stuck a home barometer in the middle of the storm, the needle would be stuck pointing to the bottom (unless yours goes beyond the "stormy" notation for pressures in the 28" range and has a category called "Run like the wind...that is surely coming to your home". I'd like to see that barometer for two reasons. One, that it has that category and two, that it actually fits all that text on there :) )

Anyway, that might seem quite historical, but storms in the fall and winter can get down into the 940s and 950s for central pressure out in the Gulf of Alaska. They typically weaken long before they hit land and are mainly just a headache for mariners in the area as those storm do produce 40-50 foot waves in the vicinity of the storm, not to mention ferocious wind.

Sure enough, here is the model a few days later. Our 948 mb monster is now a more manageable 984 mb by the time it reaches the northern Alaska Panhandle:

Low Pressures Not Just For The Pacific Ocean

Speaking of deep low pressure, we have a fairly rare situation of a very intense low pressure centered right over the Midwest!

Duluth, Minnesota, right in the eye of the low, reported a central pressure of 961.1 mb Tuesday afternoon -- that's 28.38" on the barometer!  And again, a reading that if measured in a hurricane would make it a Category 3. This storm is bringing very severe weather across the upper Midwest and into the Northeast this week and 81 mph winds.

UPDATE: National Weather Service confirms this storm has the lowest central pressure reading in the mainland U.S. of any non-tropical storm in U.S. history. That means worse than the pressure that produced the Blizzard of 1978, the March 1993 "Storm of the Century" or the November 1975 storm that sank the Edmund Fitzgerald freighter, memorialized in a song by Gordon Lightfoot.