Wasatch Weather Weenies

Source: Markowski and Richardson (2014) Paul Markowski and Yvette Richardson of Penn State have a great article out in the latest Physics Today entitled " What We Know and Don't Know about Tornado Formation ."  I suspect the article may be paywalled, but it should be accessible to anyone on the University of Utah campus or from other institutions that have a suitable license.  I especially encourage atmospheric and other science majors to have a look. Paul and Yvette are at the forefront of tornado and severe convection research in the United States and are also known as being outstanding teachers.  They work on different problems than I do, but when I can, I always attend their talks.  The are also the authors of the popular textbook Mesoscale Meteorology in Midlatitudes .

Blue skies prevail over the Wasatch Front this morning, marking an end to our latest flirtation with the tropics.  This weeks monsoon surge produced some incredible flooding and videos, such as the one below from Shane Dukeman in the Virgin River Gorge (Warning: Disturbing scenes and strong language).  The status of the man who disappears with the van is unknown, but officials in Nevada report no deaths. With the tropical airmass gone, it's time to start thinking about skiing again.  The Utah Avalanche Center (UAC) is currently conducting a survey on avalanche danger ratings.  Please consider taking the two minute survey at at  https://www.surveymonkey.com/s/WLHSRHS .  In addition to their usual clientele, they are especially interested in hearing from individuals who are not already familiar with their danger ratings.

The climate of the desert southwest is characterized by long stretches of monotony broken by periods of intense excitement. Intense excitement prevailed yesterday as heavy rains brought flooding to locales such as Palm Springs (CA), Las Vegas (NV), the Virgin River Gorge (UT), and Phoenix (AZ).  Given the large spatial contrasts that exist in monsoon precipitation, the event was about as widespread as a monsoon precipitation event can get. Phoenix has gotten a great deal of attention and for good reason.  The Phoenix Airport recorded 3.29" of rain for the day, all falling in about 7 hours.  Accumulations of over 2 inches covered a large portion of the metropolitan area with some locations reporting more than 5 inches. Source: NWS The time series of accumulated average (brown line) and actual (green line) precipitation since the start of the water year (October 1, 2013) shows the feast or famine nature of the Arizona climate.  Average looks nice and smooth, ...

Someone was going to get a beating from the ongoing monsoon surge and right now it is Phoenix.  Observations from the Phoenix International Airport (KPHX) show that 3.09" of rain has fallen since midnight. Source: NWS The NWS has issued flash flood warnings for much of the area. Source: NWS The 1200 UTC (0600 MDT) analysis below shows the mix of airstreams feeding the storm system, known as a mesoscale convective system , this morning.  Potentially contributing to this event are moisture sources associated with Tropical Cyclone Norbert, a Gulf of California surge, and even the Gulf of Mexico, although the juiciest air appears to be originating from the Pacific and the Gulf of California. The potential for thunderstorms that could be locally heavy exists across much of Utah today through tomorrow.  Keep an eye to the sky.  NWS forecasts at  http://www.wrh.noaa.gov/slc/ .

You can say "yeah, but it's a dry heat" all you want today, but the reality is that it will be quite humid (by local standards) in many parts of the desert southwest today and tomorrow. This morning (1500 UTC/0900 MDT), the decaying circulation of former Hurricane Norbert (now Tropical Storm Norbert) sit off the Baja coast.  A major slug of moisture (integrated precipitable water contours below illustrate the total water vapor in the atmosphere) to Norbert's northeast is now pushing into the lower Colorado River Basin and the surrounding region. The corresponding higher-resolution 3-hour forecast of integrated precipitable water and surface wind from the NAM shows the complex stew of water vapor that will be influencing the southwest the next couple of days.  Yeah, integrated precipitable water values are high around Norbert, but there is also a related surge of Gulf of California moisture into the lower Colorado River Valley and moisture originating to t...

Like a child coming of age in Divergent, as a forecaster one choice can transform you and today that choice is do I join the GFS faction? The GFS continues to be a dauntless like outlier amongst the various models with regards to the evolution of Hurricane Norbert.  It continues to hold on to a solution in which the remnants of Norbert make landfall near San Diego on Monday. Source: Wundermap This contrasts with the gold-standard ECMWF solution Source: Wundermap and even the, gasp, NAM. Source: Wundermap I'd show the Canadian, but it's pretty much a repeat of the ECMWF and NAM with Norbert tracking more slowly to the northwest and well off the SoCal coast on Monday. The pros at the National Hurricane Center are clearly leaning toward the non-GFS solution and keep Norbert well south of San Diego through Monday. Like Beatrice Prior in Divergent chosing Dauntless, perhaps Mother Nature will "chose" the GFS faction.  More likely she will stic...

The most recent satellite loop shows that trouble is brewing in the tropics in the form of Hurricane Norbert and a potent slugs of high precipitable water (a measure of the total water vapor content of the atmosphere) over both the eastern Pacific and the Gulf of Mexico. 1200 UTC 2 Sep – 1200 UTC 4 Sep 2014 IR satellite imagery with GFS analyzed precipitable water contours every 5 mm Model forecasts for the next several days, however, differ depending on how each model handles an approaching upper-level trough in the midlatitude (i.e., extratropical) westerlies.  The upper-level trough digs in the GFS, eventually leading to large scale southwesterly flow over the eastern Pacific and southwest U.S.  As a result, Norbert tracks quickly northward and eventually curves toward SoCal coast, potentially bringing heavy rains to the area on Monday.  If the GFS forecast were to verify, gusty winds would likely accompany the Norbert remnants as they make landfall, but winds wo...