Showing posts with label Wind. Show all posts
Showing posts with label Wind. Show all posts

Tuesday, April 29, 2014

A Big Honkin' Ridge

The atmosphere is transitioning into outlier mode this week with the development of a remarkably high amplitude wave pattern at upper levels.  The impacts of this anomalous pattern are already being felt in the western United States.

The loop below shows the development of the high amplitude pattern over the past couple of days.  Note the amplifying upper-level ridge along the US West coast (black 500-mb height contours) and the strong high pressure system forming at the surface and eventually centered near the ID–MT boarder (color sea level pressure contours).

This pattern is already having a major impact on southern California with the resulting pressure gradient driving strong Santa Anna winds.

The strongest winds I've been able to find thus far are at Sill Hill at 3556 ft east of San Diego with a peak gust of just over 80 mph.

Given the drought conditions present over California, let's hope that they escape this event without any fires.

The ridge is expected to amplify through tomorrow afternoon [1800 MDT 30 Apr (0000 UTC 1 May)], with the overall pattern forming an omega-block like pattern over the eastern Pacific and North America (note the omega shape below).  The strength of the ridge over the Pacific Northwest and southwest Canada is quite unusual for this time of year with 500-mb heights of this magnitude unobserved over the past 30 years during the 3-week period from 20 April to 11 May. 

This will result in unusually warm spring weather for the Pacific Northwest (more on this "heat wave" at the Cliff Mass blog).  In fact, maximum temperatures in the lowlands west of the Cascades will approach or exceed 80 at many locations.  How about these forecasts from the National Weather Service for Portland and Seattle (I've truncated the stuff past Thursday). 

The ridge axis will eventually move over Utah (in somewhat weakened form), so we will see temperatures on the rise throughout the rest of the week. 

Friday, April 25, 2014

Pretty Good Forecast

Following up on this morning's post, I thought I'd show that the HRRR is doing quite well for this event.  Below is the "analysis" for 2035 UTC (0235 PM MDT).  I've added a blue line showing a somewhat convoluted leading edge to the southerlies (note that I've ignored mountaintop obs for this analysis).  The southerlies have entered the southern portion of the Dugway Proving Grounds, have met the Great Salt Lake Breeze in the northern Tooele Valley, and have penetrated into the western Salt Lake Valley.  Note that the flow in the eastern Valley is either light southerly, easterly, or northwesterly.

The HRRR image I have from this morning's forecast is technically for 2130 UTC (55 min later), but still is a remarkably good forecast, especially with regards to the strong southerlies pushing northward into the Tooele Valley and western Salt Lake Valley.

The one quibble one might mike is that the surge of southerlies might have been a bit slow compared to observed (note that the observed southerlies have penetrated a bit farther north than forecast for about an hour from now).  Nevertheless, this is a good harbinger for the future of numerical weather prediction.

A Glimpse at the Future

Yesterday's post discussed some of the uncertainty in the forecast for today (Friday) and Saturday.  At issue for today was the position of the trough that was expected to develop over the Great Basin and extend downstream from the Sierra Nevada into northwest Utah.

Currently, that trough is located to the south of the Salt Lake Valley with northerly flow evident across much of northern Utah.  It is difficult to nail down the precise position during the early morning hours when shallow cold pools and drainage flows in the valley obscure the large-scale wind direction, but if I had to give my best guess I would probably put it somewhere in Utah county.

That's a bit south of where the models had it yesterday, but as I said, this was an event where one needed to recognize there was uncertainty in the forecast trough position.

Now I want to share with you some amazing images from a new forecast model called the High Resolution Rapid Refresh, known as the HRRR (pronounced "her").  Developed at the NOAA Earth Systems Research Laboratory (ESRL), the HRRR has 3-km grid spacing, radar data assimilation, and all sorts of other goodies that should allow it to become a game changer when it is finally implemented as an operational model at the National Centers for Environmental Prediction (NCEP).  Unfortunately, there have been numerous delays in the acquisition of a new computer at NCEP (see this post by Cliff Mass for why), but one can access the experimental version run at ESRL.

Those of you with a lot of bandwidth can access a monsterous loop of HRRR forecast surface winds for today by clicking here (it's worth a look).  Otherwise, just have a look at the two images below, which are wind forecasts for 2130 UTC (330 PM MDT) and 0100 UTC (700 PM MDT).  At 2130 UTC, note the dramatic transition between the strong southerly flow and the lighter flow to the north, with the boundary extending just into the southwest Salt Lake Valley.  Other tidbits here include downslope flow to the north of the Uintas (encircled by ligher flow) and numerous shear boundaries related to flow interaction with the topography.

By 0100 UTC, the boundary has pushed just a shade further north (quite a bit further north over Dugway Proving Ground), but remains just south of the Great Salt Lake.  Meanwhile, a front is pushing into western Utah from Nevada.

We will have to see how well the HRRR does on this event, but it has great potential to revolutionize short-range forecasting over Utah, as well as other parts of the continental U.S.  I'm hoping to integrate it into blog posts coming in the future - especially those related to snow!

Tuesday, April 22, 2014

The Warm and then the Storm

Last night was remarkably warm with a minimum temperature of 63ºF at the Salt Lake Airport occurring at about 11 PM.  That's the average high for today. Given that we will be cooler than that this evening, it won't stand as the official minimum for the calendar day.  

This morning's sounding shows a surface temperature of 68ºF and about the weakest nocturnal stable layer possible.  Conditions above that stable layer are what meteorologists call "well mixed" to about 500 mb.  As soon as we mix out that shallow stable layer, we're going to see wind gusts picking up in strength.  

Source: NWS/Storm Prediction Center
Expect a warm, windy day today in advance of an Intermountain cold front that will be intensifying as it approaches northern Utah.  The NAM forecast below shows the front moving into northwest Utah at 3 PM, near ideal timing for maximum frontal intensity.  

Winds both ahead of and immediately behind the front should be quite strong.  The NWS is calling for gusts in excess of 60 mph across much of the western half of the state, including the Wasatch Front.  It will be interesting to see how much dust this kicks up and whether or not we get into a plume. 

After a high in the early afternoon today near 75ºF, the bottom falls out with and following the cold frontal passage.  NAM 700-mb temperatures drop from about +6ºC at noon to -7ºC by midnight, and then even a bit colder. If the forecast below verifies, we will see flakes on the benches with a coating possible on cold surfaces and the grass by morning.  Ah, spring!

Yesterday, the GFS was quite a bit warmer than the NAM following frontal passage, but appears to have shifted toward the colder NAM solution.  No complaints here as I like my cold fronts to be as strong as possible.  

Sunday, April 13, 2014

Overnight Blow

Some strong winds accompanied a band of showers and thunderstorms that moved through the Salt Lake Valley just after midnight MDT/0600 UTC last night.

Source: NCAR/RAL
The award for highest lowland wind gust goes to the Meteorological Solutions Inc. observing site in Olympus Cove where a peak gust of 63 mph at 0105 MDT/0705 UTC. Note the dramatic drop in temperature and increase in wind speed.

Source: MesoWest
Other peak gusts include 60 mph on the Eyring Science Center @ BYU, 60 in Vernon, 57 at the University of Utah, and 52 at the Salt Lake City International Airport.  

Two inches of snow at Alta combined with the cooler weather should yield some "interesting" dust-on-crust conditions in the Wasatch for today.  

Thursday, October 3, 2013

Recipe for a Blizzard

Again, I am remiss today in ignoring the weather for later today and tonight in northern Utah, but in addition to the potential impact of Karen on the Gulf states discussed in the previous post, we have a truly remarkable winter storm set to rumble across Wyoming and the Dakotas, with blizzard conditions expected in some areas.  The storm will start with rain in some areas, but most of Wyoming and the Dakotas will eventually see snow as colder air moves in and precipitation rates intensify.  This is a very powerful early season storm with all the key ingredients for interstate gridlock and dangerous travel conditions:

  1. Strong lee cyclogenesis over eastern Colorado with cold high pressure to the north and northwest
  2. A strong intervening pressure gradient with strong surface winds across Wyoming and the Dakotas
  3. Heavy precipitation rates
Check out the GFS forecast for 0600 UTC (0000 MDT) 4 October through 0600 UTC (0000 MDT) 5 October.  Yeah, those are some big precipitation totals with some very strong winds.  

It's not going to feel like October 4th in this part of the world tomorrow.  This is a very serious storm with winter storm conditions about as bad as they can get.  

Sunday, December 2, 2012

A Blustery Fall Day

Wave clouds over the Wasatch at Sunrise
I love days when I wake up to a rattling house and wave clouds over the Wasatch.  Today we have a cold front moving into the western United States, with a very strong low-level pressure gradient moving into northern Utah.  

1200 UTC 2 Dec 2012 IR satellite imagery and sea level pressure analysis
In this case, that pressure gradient is oriented in a way that will drive strong flow in the primarily north-south oriented valleys of northern Utah.  Indeed, one can see a southerly low-level jet, with a peak wind speed of more than 40 knots, centered at about 800 mb (about 700 m above the valley floor) over the Salt Lake Valley in this morning's sounding.  

Winds will pick up this morning as the surface warms and turbulence mixes down some of that stronger flow.  So, if you haven't bothered to rake your lawn, your leaves should be in for an interesting ride.  

Monday, August 13, 2012

Is The Answer Blowin' in the Wind?

Brazos Wind Farm, Texas.  Source: Wikipedia Commons.
Wind power in the United States exploded in the past few years, with capacity doubling since 2008.

Source: Wikipedia Commons
It was a boom time and jobs were plentiful.  According to the American Wind Energy Association, there are about 400 companies generating wind turbine components and about 75,000 jobs in the wind industry.   I have a number of friends who migrated to wind power jobs during this period.  For meteorologists and fluid dynamicists, opportunities existed in wind prospecting, farm design, turbine design, forecasting, you name it.

However, as can be seen in the graph above, installed new capacity peaked in 2009 and The Guardian reports today that while total US wind power capacity eclipsed 50 Gigawatts this year, layoffs are occurring throughout the sector because of a possible expiration of a wind power production tax credit at the end of 2012.

Extension of the wind power production tax credit is presently under consideration by Congress and it has become a subject of considerable political debate as it falls in the crosshairs of energy policy, tax policy, alternative energy subsidies, deficit concerns, etc. (see articles here and here).  The resulting industry uncertainty is stalling investment, delaying projects, and leading to layoffs.  Is this a short-term blip or a more serious long-term stalling of an industry attempting to produce 20% of the US power supply by 2030?  The answer my friends isn't blowin' in the wind, but in the smoke-filled rooms of Washington.

Saturday, July 21, 2012

Change at the British Open

Of the four golf majors, the British Open is most infamous for bad weather.  This year, however, the weather has been benign, and that continues today at Royal Lytham and St. Annes Golf Club.  Nevertheless, change is coming and the golfers will be facing dramatically different conditions tomorrow.

Royal Lytham and St. Annes is located on the eastern shore of the Irish Sea, just north of Liverpool (see A thumbtack below).

As shown by the GFS analysis for 0600 UTC this morning, high pressure is firmly in control today, as was the case for the first two rounds.

However, a strong surface cyclone will be tracking toward Iceland tomorrow, and southwesterly flow will be on the increase in the British Isles tomorrow.  The GFS forecast for 1200 UTC puts Royal Lytham and St. Annes ahead of an approaching cold front, but in strong southerly flow.

Winds will be increasing during the day and by noon will likely be gusting to near 30 miles per hour.  Those hoping to wind the Claret Jug are going to need to adapt to dramatically different conditions  (Adam Scott presently is up 3 strokes, but no lead will be safe tomorrow).  Unlike the first 3 rounds, it will be absolutely essential to keep the ball low and on the ground.  Those who can make that adjustment will minimize damage, which is probably going to be the key to winning tomorrow.

Thursday, May 10, 2012

Dusty Northwest Wind

A weak cold front passed through the Salt Lake Valley early this morning, ushering in a period of stiff northwest winds of about 25 miles per hour with gusts at times into the low 30s at the Salt Lake City International Airport (KSLC).

There appears to be some dust in the post-frontal environment as the mountains are somewhat obscured compared to what one would fine with a "pristine" post-frontal airmass.

Oquirrh Mountains from the Avenues Foothills
The source of dust during these weak events is unclear.  The dust is not thick enough to detect with satellite imagery.  Is it from the playa around the Great Salt Lake?  Is it of a more remote origin?  Is the dust deposited from these weak events significant relative to major episodes during strong windstorms?  These are important questions given the role of dust in the ecology and snow hydrology of the region.

Thursday, April 12, 2012

Southeast Utah Weather and Climate

Sorry to abandon everyone the past few days.  The kids are off school and we've been on a camping trip in southern Utah.  There was plenty going on weather and climate wise.  First, there was Lake Powell, where we found the pool elevation is down a bit compared to the last time they were running the Bullfrog Ferry.

Based on this chart from the Bureau of Reclamation, that appears to be fairly typical for this time of year as the runoff is just about to begin.  Presently, Lake Powell is down about 25 feet compared to the high stand last year.

While Lake Powell is a man-made wonder, one doesn't have to wander far to find natural wonders created by meteorology, hydrology, and geology.

But the meteorological high point was yesterday when south winds transported sand and dust through much of souteast Utah.

After suffering through a similar windstorm while camping near Escalante a few years ago (sadly, that tent did not survive), we opted to spend the night in a hotel in Green River and enjoy a burger at Ray's Tavern.  Besides Green River is lovely on a day like this...

Eventually, the atmosphere was full of dust and the Book Cliffs to the north were fully obscured.

Fortunately, we are back in Salt Lake and I see snow is flying in the Wasatch.  Looks like about 15 inches thusfar on the Alta-Collins stake.  Perhaps we'll wrap up the vacation with some freshies tomorrow.  

Saturday, March 31, 2012

The Dust Is Here

Thusfar, the central Wasatch have escaped the wrath of the dust, but that's not the case in the western Salt Lake Valley and southern Oquirrh Mountains, as evident in the image above, which was taken facing south from the Avenues.  Note the obscuration in the right half of the image.

One of the most prominent plumes thusfar today is to our west, appears to originate in the Skull Valley (near the diamond I've annotated), and blows off downstream over the Great Salt Lake.

There's a chance this is smoke and not dust, but I can't imagine anyone would be burning anything today with so much lead time for the high winds.  The UDOT cameras also suggest it is dust.

Thusfar, we've had a wind gusts over 50 miles per hour at several stations in the lowlands of northern Utah, with a maximum of 62 miles per hour out in Dugway Proving Grounds.  I think we'll see higher gusts over the next few hours as the storm intensifies.

Saturday, March 17, 2012

Big Blow Update

I'm back from skiing.  A couple hours of grim pickins was enough for me.  I'd rather garden and crack open a cold one to celebrate St. Patricks Day.

As anticipated, strong surface winds are developing today.  The biggest gust thusfar today, 94 miles per hour, was recorded on Ogden Peak just after midnight.  There was also a gust of 92 miles per hour at 1215 MDT.

Curiously, winds at Alta weren't too bad through 1 PM when I bolted for warmer climates.  In fact, Mount Baldy has only been gusting into the 30s over the past few hours, which is pathetic compared to the lowlands to the west.  For example, the peak lowland gust thusfar was recorded out in Dugway Proving Ground where their Causeway observing site recently hit 64 miles per hour.

Winds have been stronger thusfar today in the West Desert and the Tooele Valley than the Salt Lake Valley.  We can't get a good view of dust plumes from satellite because of the cloud cover, but UDOT's Grassy Knolls camera shows there's some out in the West Desert.

Things are only going to get more interesting from here.  

Thursday, March 15, 2012

Forecast Predictability and the Utah Sirocco

In previous posts, I have discussed some of the predictability issues associated with this weekend's storm. I still think this is a remarkably difficult forecast for northern Utah.  There's much to talk about, but I'm going to concentrate primarily on Saturday, which may prove to be a very notable weather day.

The GFS forecast for 1800 UTC (1200 MDT) Saturday 17 March puts a digging upper-level trough off the California coast.  Strong southwesterly flow ahead of this feature contributes to the development of a strong Intermountain cyclone centered near Wendover.

Yesterday's model forecasts for Saturday placed the frontal precipitation band associated with the cyclone in various locations (see previous post), which reflects one of the predictability challenges for this event, determining where the cyclone and frontal band will be located.  The GFS forecast from last night keeps the frontal band to north and west of Salt Lake City and the central Wasatch through Saturday evening.  Similarly, so does this morning's NAM, which puts the cyclone center over the West Desert at 0000 UTC 18 March (1800 MDT Saturday 17 March).

While we can't rule out the front sagging a bit further south, especially on Friday night when the models suggest it comes close before being shunted back north (not shown), the model consistency I'm seeing suggests the Salt Lake Valley and central Wasatch will remain in the warm, windy airmass ahead of the Intermountain cyclone and front through Saturday evening.   We could see some valley rain/mountain snow showers pop up in the southerly flow, possibly accompanied by a little thunder and lightning.

In addition, there is significant potential for high winds across much of western Utah on Saturday, including the Salt Lake Valley and Wasatch Mountains.  The GFS forecast above calls for 55 knot (27.5 m/s) at 700 mb near Delta, with a very strong sea level pressure gradient (nearly 12 mb from Page, AZ to Wendover).   The NAM is also "breezy."  This is a recipe for strong southerly winds and dust, which I like to call the Utah Sirocco as it reminds me of the Mediterranean Sirocco, a warm, southerly wind that often transports dust from the Sahara into Europe.

Beyond Saturday, it remains a very difficult forecast with a wide range of possibilities.  This is a situation where the moisture accompanying the system is torn up into pieces and predicting position, timing, and intensity is very difficult at these long lead times.

Wednesday, February 29, 2012

Strong Valley Flow

There is a very strong pressure gradient ahead of the approaching cold front that is driving strong southerly along-valley flow in many of the valleys of northern Utah including the Salt Lake and Tooele Valleys.  The strong pressure gradient is evident in the 1800 UTC (1100 MST) sea-level pressure analysis below.
Source: NCAR/RAL
It has been fairly windy in the Salt Lake Valley this morning.  In fact, the wind gusts on the valley floor are nearly as high as at some mountain site.  For example, at 1100 MST, winds at Salt Lake City International Airport were gusting to 43 mph, while at the top of Mount Baldy in upper Little Cottonwood, an extremely exposed ridge-top site, they were only reaching 50 mph.  Looking at the gusts in the map below (red text), you can see a number of valley sites with gusts comparable to or higher than observed at many upper-elevation sites in the Wasatch Mountains (ignore the 59 mph gust in Sandy which appears erroneous).

Source: NOAA/NWS
The crest-level flow will, however, be picking up with the approach of the cold front during the day today, leading to dendrite armageddon, the destruction of the blower pow that fell yesterday, throughout the range.  Fortunately, more snow is coming.  

Sunday, May 15, 2011

Hatu Winds and Blowing Dust

We've gone from a morning canyon wind event to an afternoon with screaming southerly winds.  I always wanted to call these strong southerlies the "Intermountain Scirocco" as they bear many similarities to the Scirocco winds of North Africa, but Mark Eubank once told me he called them the Hatu winds for Utah spelled backwards.  Hatu it is...

First, let's have a look at some of the winds out there.  At 0018 UTC 16 May, several stations in the west desert and over the Great Salt Lake are reporting gusts in excess of 50 mph.

0018 UTC 16 May MesoWest surface plot.
Wind gusts in mph annotated.
Grassey Knolls along I-80 just west of the Cedar Mountains had a peak gust earlier today of 66 miles per hour.  Not exactly fun for high profile vehicles.

The nearby UDOT traffic camera shows dusty conditions too.

Where is this dust coming from?  Well, a lot of it appears to be coming from three point sources in southern Utah, as evident in this enhanced MODIS image.

Source: NRL
I suspect the biggest offender is the Sevier Lake bed, which has played a role in Salt Lake dust storms in the past.  Thus far today, the flow has been southerly and the dust plume has been west of Salt Lake, but that's changing now as the flow is veering to southwesterly and the Oquirrhs have just disappeared.  I suspect we'll be seeing dust in the Salt Lake Valley soon.