This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Banner image is by Ludie Cochrane..

Susan Kieffer can be contacted at s1kieffer at gmail.com

Wednesday, December 19, 2018

An unusual tornado in the state of Washington!!

From baynews9.com, no copyright information given on site
About 25 miles as the crows fly, clouds were so dark and ominous yesterday afternoon that I was having flashbacks to the low dark clouds of the midwest during tornado season--April, May.... But no! It was the setting for an unusual and rare hurricane in the state of Washington (we typically have 2.5 tornados/year and they tend to be out in the plains of eastern Washington). The tornado touched down in Port Orchard on the Kitsap peninsula.
       As of today, they've estimated it was an EF-2, with winds possibly up to 130 mph. It traveled 1.4 miles. One radio broadcast today said that they have over 400 structures to evaluate for damage, and they have to do it in a rush because another wind storn us expected tomorrow night (the last one left 100,000-200,000 people without power for hours). Note in the photo how shallow the root system is on our big evergreen trees.
     As usual, Cliff Mass, atmospheric sciences professor at the University of Washington, has posted a detailed analysis of this event and I recommend it for details.  The interesting dynamics that he emphasizes are that none of the settings that meteorologists look for were flashing alarm bells: (1) there was an area of high reflectivity (=heavy precipitation) over Port Orchard, but nothing particularly distinguishing it from other convective cells. (2) The strength of the convective cell, as measured by its height, was "pretty wimpy"--15,000-20,000 feet. (3) Doppler radar imagery showed only a weak hint at rotation, an essential component for spinning up a tornado. (4) The CAPE values indicating available potential energy were modest; (5) There was no sign of the "hooked echo" in the reflectivity.  (6) Wind shear did exist, but was modest. This was not a super-cell thunderstorm.
    The wind shear existed in the lee of the Olympic Mountains. Weak winds existed east of the Olympics (in the lee side of the Cascades) and stronger south-westerly winds came around the southern flanks. As one of the convective cells moved into the lee of the Olympics, it ingested the air containing the shear and spun up into the tornado.
     The National Weather Service did not issue a tornado alert but, interestingly, a group "Washington Weather Chasers" sent out an alert to their subscribers at 1:37 p.m. warning of a "strong rotating thunderstorm moving into the ares. Will be south of Port Orchard around 1:50 p.m...." About 10 minutes later, the tornado touched down. Good work WWC!