Gulf of Alaska Storm Season Begins

Some of the most ferocious storms of the planet develop in our backyard:  the Gulf of Alaska.

Storms that are not hurricanes or typhoons but capable of producing winds and waves comparable to Category 3 tropical storms.

And one will occur in a few days.

The satellite imagery of these storms is remarkable, as illustrated by a powerful example from September 26, 2012.  Masses of frontal clouds swirl into the low center, not unlike water circling into a drain.  The low center is in the center of the swirl.  

The energy source of these powerful storms comes from contrasting cold and warm air, with warm southerly flow in front of the storm and cold air circling behind.  The popcorn-like, modeled cloud field south and west of the low center in the above picture indicates cold, unstable air.  This storm had plenty of fuel

The central sea-level pressure in Gulf of Alaska low centers can drop as low as 930 hPa (hectopascals, also known as millibars).   Such pressures are similar to the central pressures of major hurricanes. The strongest storms to hit the Northwest rarely get down even to 980 hPa.   

And then there are the winds.   Gulf of Alaska storms can possess gusts to 80 mph or more and sustained winds reaching 50-70 mph.   Associated ocean waves that have exceeded 100 ft.

Autumn is actually a favored time for Gulf of Alaska storms, something illustrated in these figures from a climatological study (Mesquita et al. 2010).  This figure shows the relative number of storm tracks, for each season.  The lower right is fall.  Gulf of Alaska watch out!

This Week

A very energetic Gulf of Alaska storm will form later this week.    The latest National Weather Service GFS model run, valid 11 PM Friday, shows an impressive 947 hPa low center, just south of Alaska with sustained winds reaching 64 knots.   Just achieving category 1 hurricane strength (sustained winds of 64 knots or more).

The European Center model is also going for a big storm, but a bit weaker and further to the east.

This is a rapidly intensifying storm (it was 992 hPa only 24 h before) and thus is called an atmospheric BOMB.  Atmospheric bombs must deepen by at least 24 hPa in 24 h.  This one doubles that.  Impressive.  Very impressive.

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Last Chance to Take My 101 Class as an ACCESS STUDENT

As I noted in previous blogs (see repeat below), I am teaching atmospheric sciences 101-- the introductory class in weather and climate-- this fall. Class starts tomorrow!

If you are over 60 and a Washington State resident you can take it as an ACCESS student for very little cost (normal fare would be around $1800).  You can attend the class in person or over zoom.

ACCESS students don't officially get registered until 3 days into the quarter, so if you are going to register, send me an email and I will send you the zoom link so you won't miss the first class.  Classes will be recorded.

Atmospheric Sciences 101

Like last year, I am teaching atmospheric sciences 101:  a general introduction to weather and climate, this fall.  You can learn more about the class on the class website.  I talk about everything from the basics of the atmosphere to weather prediction, thunderstorms, hurricanes, and local weather to global warming and climate.

I will be teaching the class in person at the UW, but will also make it available over zoom.  Thus, folks can take it remotely.

If you are over 60, you can take the class through the ACCESS program for a very nominal charge (something like $15).   Last year I had over 125 folks do so.

So if you are a UW student looking to learn about weather or a non-student interested in the topic, I welcome you to join me this fall.  My first class is on September 29th.