High Wind Shear Rips Apart Tropical Storm Sandra

Something to give thanks for this holiday weekend: Tropical Storm Sandra was shredded apart by 50 knots of wind shear early Saturday morning before the storm could make landfall on the Pacific coast of Mexico, ending the reign of this most unusual late-season storm. Earlier in the week, record-warm ocean waters helped Sandra set the record for the latest major hurricane ever observed in the Western Hemisphere, as the storm maintained at least Category 3 strength from 21 UTC November 25 through 03 UTC November 27 (previous record: an unnamed Atlantic hurricane in 1934 that held on to Category 3 status until 00 UTC November 24.) When Sandra peaked as a Category 4 storm with 145 mph winds on November 26, it became the latest Category 4 storm ever observed in either the Eastern Pacific (previous record: Hurricane Kenneth on November 22, 2011) or the Atlantic (previous record: "Wrong Way" Lenny on November 18, 1999.) Prior to Sandra, the strongest East Pacific hurricane so late in the year was 1983’s Winnie, which topped out on December 6 at 90 mph winds. Sandra was also the first major hurricane in the Western Hemisphere that has ever been observed on Thanksgiving Day. Sandra was the record-shattering 25th Category 4 or stronger tropical cyclone in the Northern Hemisphere in 2015. According to wunderblogger Dr. Phil Klotzbach's Twitter feed, the previous record was eighteen such storms in 1997 and 2004.


Figure 1. MODIS satellite image of Hurricane Sandra taken at approximately 2 pm EST November 27, 2015. At the time, Sandra was a Category 1 storm with 80 mph winds, and was rapidly being shredded apart by high wind shear. Image credit: NASA.


Figure 2. Projected 3-day precipitation totals (rain and melted snow/sleet) for the period from 7 am EST Saturday, November 28, through Tuesday, December 1.

Moisture associated with Sandra fuels heavy rain event over Texas
Moisture streaming ahead of Sandra from the tropical Eastern Pacific into the Southern U.S. contributed to a heavy rainfall event over Texas and Oklahoma on Thursday and Friday, and this tropical moisture will continue to fuel heavy rains across portions of Arkansas, Mississippi, and Tennessee during the remainder of the holiday weekend. The rain of 3.45" that fell Friday on Dallas-Fort Worth gave them their wettest November calendar day on record, their wettest November on record (7.99" so far, previous record 7.94" in 1918), their wettest fall on record (now up to 19.95"), and their wettest year on record (now 56.91", previous record 53.54" set in 1991.) Thanks go to TWC's Michael Palmer for these stats.

Have a great rest of your Thanksgiving weekend, everyone!

Jeff Masters