Friday, May 24, 2019

High Winds in Northern Utah

Easterly flow caused high winds to northern Utah on 23 May 2019 and with it, many power outages (KSL story).

This picture is from my grandpa's backyard in North Logan. Winds knocked down many trees and fences in the neighborhood...


At 0700 UTC (1:00 AM local time), winds gusts exceeded 60 MPH in Brigham City.

Maximum wind gusts exceeding 40 MPH for the previous 24 hours at 1800 UTC (12:00 PM local time) are shown below...

The HRRR forecasts compared with HRRR 3-yr climatology shows this was an exceptional wind event for this time of year and location. Below shows that the wind speeds in northern Utah exceeded the 95th percentile wind speed by over 10 m/s.
Area Forecast Discussion 
  National Weather Service Salt Lake City UT 
  413 AM MDT Thu May 23 2019 
   
  .SYNOPSIS... 
  The unsettled weather pattern with a trough over the western  
  United States will continue through Friday. There will be  
  somewhat of a hiatus Saturday into Sunday as the trough redevelops 
  a little farther west allowing a drier southwest flow aloft to 
  prevail. This new trough will move across Utah early next week. 
   
  && 
   
  .SHORT TERM (Through 00Z Monday)...Strong easterly winds have been 
  blowing overnight across the northern Wasatch Front and Cache 
  Valley. These winds are expected to remain strong through at least 
  early morning as the 700mb winds remain above 35 kts from about  
  Brigham City northward as well as across the Cache Valley. Farther 
  south the winds have not been as strong as the 700mb winds near  
  the Ogden area were forecast to only be 30 kts earlier this  
  evening and are forecast to be down to under 20 kts by mid  
  morning. May be able to drop the High Wind Warning highlight  
  sooner than later, especially for Davis and Weber counties. The  
  strength of these easterly winds downsloping along the northern  
  Wasatch Front and Cache Valley has prevented showers from  
  occurring overnight, but as these winds relax and the instability  
  of the cold pocket aloft moves in from the south later this  
  morning through this afternoon showers will become widespread.

Area Forecast Discussion 
  National Weather Service Salt Lake City UT 
  1033 AM MDT Thu May 23 2019 
   
  .SYNOPSIS... 
  The upper level low pressure over northwest Utah will maintain  
  unsettled weather across much of the region through early Friday. 
  The low pressure will exit the area and bring a break in  
  widespread precipitation Friday night through the weekend. The  
  next storm system will move across Utah early next week. 
   
  && 
   
  .DISCUSSION...The upper trough centered over the Great Basin is 
  showing multiple circulation centers this morning. These 
  circulations will consolidate into one center over northwest Utah 
  this afternoon, then lift northeast toward the northern Plains   
  later tonight through Friday. A residual upper trough will remain 
  behind the exiting upper low, with this feature merging with the 
  next upper low moving into the Pacific Northwest early in the 
  weekend.  
   
  The canyon/downslope high wind event for areas north of SLC is  
  winding down late this morning. Decreasing easterly near 700 mb  
  winds and the retreat of the tight northeast surface gradient back 
  into western/central Wyoming signals the end of the strongest  
  winds, though gusty easterly winds will continue through around  
  mid-afternoon. Will keep the current High Wind Warning going  
  through the scheduled expiration at 19Z.

Thursday, May 23, 2019

Wet spring and active weather all month long

It has been a very wet spring. I measure rain in my rain gauge just about every morning. Since the beginning of April, I have measured 4.81 inches in Provo. There is actually a little little more because I accidentally spilled the water out of the gauge before I got a measurement.

At my Davis weather station in Spanish Fork, I have measured 4.44 inches since June 1st. (Had to get this info from Weather Underground because WeatherLink doesn't let me see this anymore without paying for my own data I send to them; just a little upset).

Why so much rain this year? I remember in my synoptic meteorology learning that the more wave numbers you have the more active and progressive systems are. We definitely have a high wave number in the northern hemisphere, 6+, and that means storms roll through quickly. Maybe I should dust off my synoptic meteorology notes and get a refresher on this. I'm very rusty.


Monday, May 6, 2019

Impacts of high-frequency radar-derived wind observations on COAMPS® forecasts

I recently submitted a proposal for the National Research Council Research Associateship Program (http://sites.nationalacademies.org/pga/rap/). The proposal is to work at the Naval Research Laboratory in Monterey, California as a post-doctorate researcher on a data assimilation project.

The full application can be found here: https://1drv.ms/b/s!AtJL0JL_rT9judo3fc85wl5SkgOIiQ

Abstract

Shore-based high-frequency (HF) radars are routinely used to observe ocean currents and surface wave characteristics remotely. Because surface waves are closely related to near-surface winds, many investigators have explored methods in deriving winds from HF radars, with limited success until now. Most recently, a technique has been developed that uses HF radar Doppler spectra data with the adjoints of a HF radar model and a wave prediction model to derive winds. This technique has been applied to HF radar data collected along the Santa Barbara, California coast during October 2017. These remotely sensed near-surface wind observations are likely to be valuable in initializing mesoscale analyses and forecasts in the littoral zone, as satellite-derived surface winds are generally not available near the coast. Since ocean wave models are dependent on atmospheric winds, better forecasts of near-surface winds impact almost all Naval operations near shore—especially transits in and out of ports. This work proposes to investigate the impact HF radar-derived winds have on the quality of Coupled Ocean/Atmosphere Mesoscale Prediction System® (COAMPS) analyses and forecasts using the new COAMPS-4D Variational data assimilation system. An observing system experiment is proposed to evaluate impacts from real HF radar observations on COAMPS followed by a historical observing system simulation experiment to determine potential impacts from simulated wind retrievals.

FIG. 1 Southern California coast surface wind observation network available 14 October 2017. Locations of the HF radar network are denoted by green triangles and automated weather stations and buoys are denoted by red dots.
FIG. 2 Observed near-surface vector wind at 17:25 UTC 14 October 2017 from MetOp-B ASCAT scatterometer (black) and automatic weather stations and buoys (red). Half and full barbs denote 2.5 and 5 m s-1, respectively.



Thursday, February 14, 2019

Kelvin-Helmholtz Cloud (Wave Cloud)

This Kelvin-Helmholtz cloud phenomenon was spotted from the University of Utah campus MesoWest cameras (looking south). Wikipedia: Kelvin-Helmholtz Instability.




Friday, February 1, 2019

Polar Vortex and Extreamly Cold Temperatures

A wave of cold, artic air moved into the United States late in January 2019. Many record cold temperatures were broken. You can search on the news for that.

3-years of HRRR model analyses were used to compute empirical cumulative distributions of conditions for every hour of the year (Blaylock et al. 2018). This image show how much the temperatures at 0700 UTC on 31 January 2019 are less than the 5th percentile for the same time of year. This shows that temperatures are much more than 10 degrees colder than the 5th percentile temperature.