Update on Storm Chasing Efforts during IOP2

I like to joke that "storm chasing" Utah style involves sitting in one place and scanning storms repeatedly, which is exactly what we've been doing today for OREO IOP2.

After our overnight team returned to Salt Lake late last night, today's day team deployed to Antelope Island near the Fielding Garr Ranch.


Antelope Island is a great place to operate the DOW as there are unblocked vistas of much of the northern Wasatch and even the Salt Lake Valley.  It's a bit farther from the Cottonwoods than we like, but we can do a great deal looking at other parts of the Wasatch.

Much of the day we scanned a relatively broad frontal band.  Pretty boring by our standards, but it might still yield some interesting data.  However, during the afternoon, the flow shifted to WNW and the atmosphere destabilized, yielding some shallow convective showers. 


These showers produced a bit of graupel in downtown Salt Lake City and the Avenues (and perhapse elsewhere).


One thing we can do with the DOW is take vertical scans through storms.  The orange and yellow stuff at the bottom of the vertical scans below are ground clutter produced by mountains, but the purples are some of the convective showers, which you can see are shearing off downstream with height. 


Given a relatively pessimistic storm chasing forecast after Monday night, we'll probably work this shallow stuff to the last gasp.

Storm Chasing Update

Forget lectures and death by powerpoint.  This is what I call teaching.
Too busy to write much this morning.  We had a great night in Huntsville last night getting some very interesting data.  We are now redeploying the Doppler on Wheels to Antelope Island where we hope to get some data on today's precipitation. 

We got some great coverage last night from KUTV.  Check it out at http://kutv.com/news/local/doppler-on-wheels-helps-u-of-u-scientists-improve-weather-forecasting.

DOW7 Deployed in Huntsville for IOP7

DOW7 is now deployed in Huntsville for OREO IOP7.

The weather is perfect right now.  Radar has shown a quasi-stationary precipitation cell immediately downstream over the Wasatch crest and over our area.  For a while, it was noticeably clearer west of the Wasatch from our vantage point.

This is just the sort of thing that we're looking for and trying to better understand. Very few studies have examined lee-side precipitation processes.

Lake Superior ship tracks

GOES-16

GOES-16 “Red” Visible (0.64 µm, left), Near-Infrared “Snow/Ice” (1.61 µm, center) and Shortwave Infrared (3.9 µm, right) images, with hourly surface wind barbs plotted in yellow [click to play animation]

* GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing *

GOES-16 “Red” Visible (0.64 µm), Near-Infrared “Snow/Ice” (1.61 µm) and Shortwave Infrared (3.9 µm) images (above) revealed the presence of ship tracks across Lake Superior on 16 November 2017. Aerosols from the exhaust of ships cause a “cloud seeding effect”, which results in a higher concentration of smaller cloud droplets compared to the surrounding unperturbed clouds. These smaller cloud droplets are more effective reflectors of sunlight, resulting in a brighter white signature on the Snow/Ice imagery and a warmer (darker gray) signature on the Shortwave Infrared imagery.

A view of the entire lake — using similar Visible, Snow/Ice and Shortwave Infrared images from the Terra MODIS instrument — is shown below. In addition to the ship tracks, plumes from power plants and/or industrial sites can be seen in southern Ontario, streaming southward near Thunder Bay (station identifier CYQT) and southwestward near Upsala (CWDV); another plume was evident in northeastern Wisconsin, to the southeast of Eagle River (KEGV).

Terra MODIS Visible (0.65 µm), Near-Infrared

Terra MODIS Visible (0.65 µm), Near-Infrared “Snow/Ice” (1.61 µm) and Shortwave Infrared (3.7 µm) images [click to enlarge]

OREO IOP1 Is ON!

It's great to finally have some weather again in northern Utah.  I was woken last night by strong southerly winds, and they appear to have transported in a pretty good plume of dust this morning. 

We have a team leaving the University of Utah today at noon to begin operations for the Outreach and Radar Education in Orography (OREO) Intensive Observing Period 1 (IOP1).  Every meteorological field program needs a good acronym (hence OREO) and we usually name each observing period as an "IOP."  IOP0 is typically used for a practice IOP, which we did about 10 days ago on Antelope Island.  Since then we've been waiting on weather.

We plan to operate this evening and tonight from a site just east of Huntsville to examine the spillover of precipitation across the northern Wasatch and into the Ogden Valley.   Already, there's some interesting things happening there.  Radar imagery very clearly shows echoes developing not on the windward side of the Wasatch, but downstream.  Much of this is just sprinkles or virga, but it is a hint that perhaps there is some sort of lee wave present at the moment. 


The HRRR forecast for 1Z (6 PM MST) is optimistic, with band of precipitaiton extending across central Nevada to the northern Wasatch.  The location and movement of that area of precipitation will partly dictate the success or failure of our mission tonight.  We're hoping it is in the right place at the right time. 


Tomorrow, we may be working on post-frontal snowshowers in northwesterly flow.  We have a couple of sites selected to operate out of, but will make final decisions in the morning with updated forecasts in hand.

Keep your fingers crossed!

Low Solar Radiation: Is That Why You are Depressed?

I can't tell you how many folks have emailed me or complained in person about what they perceive as a sudden turn to darkness.  They feel depressed, tired and anxious.  Daytime light helps maintain our circadian rhythms and a number of people suffer from Seasonal Affective Disorder (SAD) when the days grow short and clouds fill the sky.

So what is the truth?  How bad has it gotten?  Let's check. 

Here is the solar radiation reaching the surface in Seattle from the wonderful WSU AgWeaherNet collection of stations over the past six months (check below).   During June and July, some days had nearly 30 MegaJoules per square meter (a Joule is a unit of energy), and even cloudy days had about 15.  But recently, we have had days with 3-4 MegaJoules....way, way lower.   And the last few days, had no real spike upward in radiation to provide relief. 


Folks are right...it HAS been dark.   Part of the problem is, of course, the turn towards more clouds the last few weeks.   But, in addition, the number of hours of daylight has progressively dropped, something shown by the figure below (the vertical white line indicates today).   We have rapidly lost daytime hours the past few months and we are close to hitting bottom.


The recent switch to daylight savings time makes it even worse, with our commute home now in darkness.

The air even feels different, with biting cool, dampness that Seattle residents fear.   Here is the plot of relative humidity for the past 6 months at Seattle.  During the past month, relative humidity has jumped to around 80-90%, resulting in not only a feeling of dampness, but a loss of visibility due to fog and water-absorptive particles in the atmosphere.

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Very dark, clouds, humid, and cool---enough to scare off many Californians, and certainly able to explain the down feelings some folks have experienced during the past week.

Core Dump on Our Pending Storm

The Doppler on Wheels (DOW) has been in town now for two weeks, and we've yet to have a significant storm during that period.  At Alta, the best we've done is 4 inches on November 4th, which isn't much of a storm.  We've kept ourselves busy with various educational and outreach activities, but are in desperate need of a storm.

Fortunately, it looks like Mother Nature will give us something tomorrow afternoon through Friday.  It's been an interesting storm to follow in the forecast models for a number of reasons.

1. It's taking forever to get here.

The GFS forecast initialized at 0000 UTC 12 November (5 PM MST Saturday) showed the upper-level trough making landfall onto the Pacific Northwest coast at 1800 UTC 16 November (11 AM MST Thursday), with precipitation across the Wasatch Mountains, Uintas, and even western Colorado.  Under this scenario, we'd want to be out storm chasing early tomorrow (Thursday).


During the past three days, however, the GFS has really slowed the progression of the trough.  The forecast from 0000 UTC 15 November (5 PM MST Tuesday) has the trough much farther west and well off the coast at 1800 UTC 16 November (11 AM MST Thursday).  Precipitation is just sneaking into the northern Wasatch and Bear River Range area, and there's no precipitation over Colorado.  Instead, we'll be able to sleep in tomorrow!


2. The Sierra Nevada really take a bite out of storms

Through flow blocking and water vapor depletion in mountain-induced rain and snowfall, the Sierra Nevada have a dramatic impact for the worse on moisture transport into the Great Basin.  This can be seen in the GFS forecast pannels immediately above.  Note in particular the how the column-integrated relative humidity in the lower left panel decreases abruptly across the southern "High" Sierra, with moisture only able to sneak in across the lower northern Sierra north of Lake Tahoe.  This effect is also apparent in theNAM forecast for the same time and, in this case, it is a contributor to the delay of precipitation spreading into northern Utah.  Without the High Sierra, moisture would penetrate more easily into the Great Basin and the Wasatch would light up even earlier.  Pity.


The time-height section from the NAM shows a classic "cloud-storm" environment tomorrow over the Salt Lake Valley.  Cloud storm is a phrase we jokingly call events with high clouds and virga, but little precipitation reaching the valley floor.  There's copious moisture at mid levels, but dry environment down low.  Deep moisture doesn't penetrate into the Salt Lake Valley until Friday night.  More evidence of further delays in the storm really getting going over the Salt Lake Valley.


Add all this up — the delay in the arrival of the trough, the drying influence of the High Sierra, and the dry low levels over northern Utah — and you have a recipe for restless natives anxious for the arrival of a storm that has been promised for Thursday.

3. Many storm chasing options

We of course have a mobile radar, so we can put it wherever we want and don't have to necessarily wait in the Salt Lake Valley for weather.  That being said, it takes time to move the DOW around and configure a reasonable scanning strategy to do real science.   We have a number of possible targets through Friday afternoon, including the spillover of precipitation across the northern Wasatch Mountains and into the Ogden Valley, multi-ridge interactions between the Stansbury and Oquirrh Mountains or Oquirrh and Wasatch Mountains, a cold frontal passage presently forecast for Friday morning, and post-frontal convection in northwesterly flow in the wake of the cold front.  It's going to be a busy time!  We'll have an interesting planning session this afternoon and then will need to keep a close eye on things in the field to maximize our opportunities.

4. Mountain snow possibilities

The situation this week has been pretty grim for skiers.  Not only has it been dry, but it has also been warm.  I don't follow the snowmaking activities at the resorts, but I suspect they were limited at best.  That situation will continue today and even tomorrow looks to be pretty warm.  In addition, the early phases of the storm when it does arrive look quite warm.  For example, the NAM forecast for 1200 UTC (5 AM MST) Friday morning has 700-mb temperatures of around -2ºC.  That equates to a snow level around 7000 feet or so.


Thus, while the upper elevations of Snowbasin are likely to get a pasting, the base may see rain for at least a portion of the storm.  PCMR may also see rain at the base during the early stages.

However, the snow level will be lowering during the period, especially on Friday.  Friday has some potential to be productive in the Cottonwoods due to cold, unstable, northwesterly flow.  Overall, the NAM-12km is generating about an inch of water and 9 inches of snow at Alta Collins through late Friday.  The numbers, however, vary widely across models and ensemble members.  At this point, I'd lean toward 6-12 inches at upper elevations in Little Cottonwood, with the potential for more if the post-frontal environment is highly productive.  Water totals in the northern Wasatch should be higher.

Snowmakers had better be ready to release the torrents Friday, Friday night, and Saturday morning.  After that, ridging returns and more marginal snowmaking conditions return for a couple of days.

Addendum at 10:15 AM 15 November

The SREF plume diagram below was unavailable when I wrote this post, but I've added it here and it shows remarkable spread for the event at Alta Collins.  Talk about forecaster heartburn!  Hope for the high members to verify.


Strong storm off the Pacific Northwest coast

* GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing *

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Nighttime images  of Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) data (above) showed an occluded extratropical cyclone off the coast of the Pacific Northwest at 1050 UTC or 3:50 AM local time on 13 November 2017. This system was producing storm force winds offshore.

A GOES-16 Mesoscale Sector had been positioned over that region, providing imagery at 1-minute intervals — the structure and evolution of the storm could be seen using Lower-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor imagery (below).

GOES-16 Lower-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images [click to play MP4 animation]

GOES-16 Lower-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images [click to play MP4 animation]

A more detailed view was provided by GOES-16 “Red” Visible (0.64 µm) images (below), with hourly wind gusts plotted in yellow. Peak wind gusts as high as 89 mph were reported within the Seattle and Portland County Warning Areas.

GOES-16 Visible (0.64 µm) images, with hourly wind gusts plotted in yellow [click yo play MP4 animation]

GOES-16 Visible (0.64 µm) images, with hourly wind gusts plotted in yellow [click yo play MP4 animation]

A comparison of Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images at 2038 UTC or 1:38 PM local time (below) showed a curved cloud band with embedded convective elements moving inland over western Washington and Vancouver Island. Note that the VIIRS instrument will also fly on the JPSS series of satellites.

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Wind Storm Update

The first...and lesser act...of today's wind event took place this morning, the passage of an occluded front associated with the offshore low.  But the main act is still in the cards, and folks should be prepared.

The infrared satellite image at 6 AM shows the swirl of clouds around the low center, located southeast of Vancouver Island.  The occluded front is indicated by the roughly north-south band of cloud over the Cascades at that time.


Heavy rain accompanied the occluded front (see radar at 2 AM), and after its passage winds surged.


The maximum winds during the last 24 hr (ending 6 AM), which pretty much happened during the past 6 hours, are impressive: several over 40 mph in the central Puget Sound, with some on the Kitsap Peninsula reaching 50-60 mph.  Even stronger winds on the coast.


 Power outages have already occurred over Seattle
 And Puget Sound Energy has about 25,000 customers blacked out, including large areas over the Kitsap.

The winds above Seattle-Tacoma Airport show the movement of strong winds aloft, some of which have reached the surface in gusts.  This chart shows sustained winds from the surface to 10,000 ft (700 hPa pressure in this figure), with time increasing to the right (in UTC, 13/12 is 4 AM this morning).  The solid triangles indicate 50 knot sustained winds.  Strong winds came in aloft overnight, and intensified with the occluded front.  Temperatures area cooling as well (think snow in the mountains).

We are now in the break before the main act.   You will even notice the rain has backed off and there will be sun breaks. Absolutely typical.  We must wait until late morning/early afternoon when the low approaches and the winds will increase again, probably exceeding what we experienced last night.

The UW has developed the Seattle WindWatch site (sponsored by Seattle City Light) to assist City Light in preparing for and managing wind outages.  One of its capabilities is to present the latest High Resolution Rapid Refresh forecast from the National Weather Service.   This system forecasts very strong winds along the coast at 11 AM (blue indicates gusts about 50 mph), with lesser, but still problematic winds (40-50 mph gusts) over the Seattle, with stronger gusts from Everett westward.
 By 4 PM, winds will accelerate further over central and southern Puget Sound.  With many leaves still on the trees and new branches untested by strong winds, expect more power outages.
Be prepared for the increasing gusts and avoid places with a lot of trees.  No biking to the UW on the Burke Gilman trail for me today!  And if you have trees around your home, expect lots of leaves down.

Überströmungs Cyclogenesis!

A classic example of Alpine lee cyclogenesis of the "Überströmungs-type" is bringing heavy snowfall to portions of the Alps and southern Europe.

Alpine lee cyclogenesis is the birth of a cyclone in the lee (downstream side) of the Alps.  Überströmungs-type Alpine lee cyclones form in northwesterly large-scale flow as cold air is blocked and flows cyclonically to the west of the Alps, while the upper-level trough continues to move downstream, inciting cyclone development in the western Mediterranean region.  Terrain impacts are especially pronounced in cyclones that form in this fashion.

The satellite and sea level pressure loop below shows the situation from 1200 UTC 11 November through 1200 UTC 13 November.  The system begins as a surface trough that plunges southeastward across the British Isles, France, and Germany.  The cold air plunges southward through the low elevation region between the Alps and Pyrenees (note faint rope cloud in the loop), and strong cyclogenesis occurs over northern Italy.


@severe-weather.EU is the feed to monitor this morning as they are tweeting out some wonderful images from across the region.  Here are a few.

 Enjoy the look at the fresh snow.  Let's hope we can join the party later this week.