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

Friday, October 23, 2015

Hurricane Patricia --Category 5 aiming for Mexico

Hurricane Patricia on Friday morning 10/23/2015, from Weather.com

As I write this, Hurricane Patricia is less than 100 miles off shore of Mexico, aiming for landfall south of Puerto Vallarta and north of Manzanillo.  Evacuations have been underway. Mexico's second largest city Guadalajara lies inland fortunately south of the projected path that will take it into southern Texas. It is expected to make landfall Friday afternoon or evening, and to fizzle out near Monterrey on Sunday.
     Patricia is a Category 5 with sustained winds of 200 miles per hour in a small area about 15 miles across near the center. For comparison, the definition of a Category 5 hurricane is one with sustained winds of 157 miles per hour, so Patricia is a strong Category 5. Individual gusts can reach strengths of 50% greater than sustained winds**, implying gusts of 300 mph or 133 meters per second.  Since the speed of sound in air is ~340 meters per second, these winds have a Mach number of nearly 0.4! Mike Smith of Accuweather has drawn the analogy that Patricia is like a 15-20 mile wide EF-4 to EF-5 tornado. Since a mile-diameter tornado is huge, this gives a feel for the size of the dangerous region of this hurricane.
     Patricia has taken the record for the lowest pressure in any hurricane ever recorded with a pressure in the eye of 880 millibars. Hurricane Wilma set the record at 882 millibars ten years ago. Patricia is the strongest hurricane ever recorded in the eastern Pacific. Rainfall amounts of 8-12" are projected with isolated instances of 20". Wave heights near shore have increased already and a dangerous storm surge is expected at the landfall site. Fortunately the inland terrain is mountainous and shear between the storm and the mountains will cause the hurricane to weaken within about 36 ours.
     Category 5 storms tend to cluster into El Nino years because warmer sea surface temperatures and reduced wind shear favor their formation, though there are exceptions.  Since this is the year of the so-called "Godzilla' El Nino, it'll be interesting to follow this season.

     For comparison, here's a link to a post that I did on Super Typhoon Haiyan two years ago, and here's a link to a list of Category 5 Pacific hurricanes.
**Landsea, Christopher W. "Tropical Cyclone FAQ Subject: D4) What does "maximum sustained wind" mean? How does it relate to gusts in tropical cyclones?"Atlantic Oceanographic and Meteorological Laboratory. National Oceanic and Atmospheric Administration. Retrieved 2006-03-16.

Various weather sites, however, are projecting maximum winds of the order of 250 miles per hour.

Wednesday, October 14, 2015

Jupiter's Red Spot is shrinking!!

Comparison of Jupiter's Red Spot
with Earth. Image from
After a 2-month hiatus, I'm going to work my way back into regular posting. But will start in a very lazy way by referring you to a really cool video here, a new NASA time-lapse portrait of Jupiter!
      Jupiter is the largest planet in the Solar System with an equatorial radius of about 11 times that of the Earth, and about 1/10 of the radius of the sun.  It is a gassy planet, and it's upper atmosphere consists of about 75% hydrogen and 24% helium by mass, with a trace of methane, water, ammonia, .... It's atmosphere spans 5,000 km (3100 miles) in altitude, though since Jupiter has no solid surface of rocks like the earth, the base is rather arbitrarily defined as the point where atmospheric pressure is about 10 times the surface pressure on Earth.
     The Great Red Spot is a vortex, an anticyclonic (rotating counterclockwise) storm that is known to have existed since 1831, and possibly since 1665 where it was reported in the very first volume of the Philosophical Transactions (of England)  that a small spot in the biggest of the three observed belts had been spotted with a twelve foot telescope. The Great Red Spot is about three times the diameter of the earth as shown in the image to the left. It "sticks out" above the surrounding cloud tops by 8 kilometers.
      For a technical paper on the topic, see Asay-Davis et al., Icarus, 203(1), pp. 164-188, September 2009, in which they show that "between 1996 and 2006, the area circumscribed by the high-speed collar of the Great Red Spot (GRS) shrunk by 15%...."