Tuesday, March 31, 2015

Satellite Meteorology talk by Prof. Steven Ackerman (CIMSS)

Steven Ackerman from the Cooperative Institute for Meteorological Satellite Studies gave this talk:

Video part 1

Video part 2

Wednesday, March 25, 2015

Mystery of Hole in the Clouds

This was several days ago, but a fun read. There was a funny clear streak in the clouds over San Antonio, Texas. What caused this? An airplane!

Read an explanation of why these form here, here, and here.

Also, check out the Cloud Appreciation Society website: http://cloudappreciationsociety.org/

Tuesday, March 24, 2015

Wind Rose by hour

Remember my wind rose for my personal weather station? Well, I took a look at the wind rose for the station at the mouth of Spanish Fork Canyon and made a comparison.

This is ten minute wind data from January 1, 2014 thru March 24, 2015.

There strongest winds occur most frequently in the early morning hours, between midnight through 9:00 AM. Then the winds begin to weaken after 9:00 AM and remain weak throughout the daytime hours until 9:00 PM when the winds begin to strengthen again.

Compare this with my personal weather station. Notice the change in color scale which reveals that the winds at the canyon mouth are stronger than at my house. Still, the transition times between weak and strong winds at 10:00 AM and 5:00 PM exist.

Plum Blossoms

Wednesday, March 11, 2015

Great Salt Lake Breeze and Lake Level

A proposal for my statistics class.

Great Salt Lake Breeze and Lake Level
Wind patterns at Salt Lake International Airport are often characterized by a thermally driven lake-breeze circulation. A pressure gradient between the Great Salt Lake (GSL) and the adjacent land causes surface winds to blow from the cool lake towards the warm land during the day. Winds reverse at night and blow from the cooled land towards the lake. Past studies and modeled simulations suggest that the strength of a lake breeze is partially dependent on the lake’s dimensions. Small lakes have weaker lake breezes than large lakes. Furthermore, lake breezes tend to occurs less frequently for small lakes because of interference from terrain or synoptic forced winds (Crosman and Horel 2010).
Lake dimensions can change over time. In the last century, fluctuations in the GSL level has caused the lake area to grow and shrink. For example, archived MODIS images show a larger lake on May 31, 1987 (left) when lake levels where high and a smaller lake on March 10, 2015 (right) when lake levels were low.

The purpose of this project to compare historical lake level measurements with radiosonde and pilot balloon wind observations to confirm the relationship between lake breeze strength and lake level. For instance, it is expected that the lake breeze will be stronger during years when Farmington Bay contains water. The results of this work may have implications for understanding how the lake area influences air quality in Salt Lake City.
Zumpfe and Horel (2007) have shown that winds at the airport generally shift to the north in the late morning or afternoon on days without precipitation. These wind shifts occur most frequently between April and October. They also show that the occurrence of lake breeze fronts in the Salt Lake Valley was more frequent when the lake level was high.
In previous publications, lake breeze strength has been quantified by the distance it penetrates inland, its vertical depth, and the on-shore wind speed. While lake breezes are influenced by several factors, numerical simulations suggest that they are especially sensitive to changes in lake dimension (Crosman, 2012). Other studies found that lakes larger than 100 kilometers across behave similarly to a sea breeze, but lake breezes for different sizes of smaller lakes behave non-linearly. For instance, a small change in lake area for a small lake will have a higher increase in wind speed than a small change in lake area for a larger lake (see figure 7d in Crosman and Horel 2012). Part of the reason of this non-linear behavior between lake size and wind speed is caused by changes in the curvature of the lake. Large curvature is associated with more diverging on-shore winds and thus weaken the lake-breeze.
The data that will be used for this project will be from weather balloons and lake level measurements. Daily, low level wind observations from balloons date from 1926 to present. That data set included 22 years not used in Zumpfe and Horel’s study. Measurements of GSL levels are available for the same time period with only one measurement per month.
We want to see if on-shore wind seed can be predicted from lake level. To analyze the sea breeze only wind observations below 1500 meter elevation (approximately 200 meters above ground level) will be used. The first thing to look as will be a linear regression between afternoon wind speed and lake level. As lake dimension sensitivity studies suggest, this relationship should be non-linear. However, the non-linear relationship may not be apparent if changes in lake area for the GSL during this time period are not large enough. Also, since lake breeze strength is dependent on synoptic and seasonal influences, I expect the relationship will be weak. Additional work will be needed to filter the data and remove the seasonal component of the lake breeze. It may be best to break the analysis up by season or month. I’ll also need to filter out days that are obviously not lake breezes. For example, afternoon winds from the south should not be considered. Other statistical methods may be used out of necessity or suggestion.

Crosman ET, Horel JD (2012) Idealized Large-Eddy Simulations of Sea and Lake Breezes: Sensitivity to Lake Diameter, Heat Flux and Stability. Boundary-Layer Meteorol 144:309-328
Crosman ET, Horel JD (2010) Sea and Lake Breezes: A Review of Numerical Studies. Boundary-Layer Meteorology 137:1-29
Zumpfe DE, Horel JD (2007) Lake-Breeze Fronts in the Salt Lake Valley. J Appl. Meteor. Climatol. 46:196-211


These are always great. Photo credit to Mom. Thanks for sharing!

Weather for this week looks good.
Wednesday: Warm, upper 60s
Thursday: Cold front comes through and will bring rain to the valleys and snow to the mountains.
Friday: Starts to warm back up, upper 50s
Saturday: Warm
Sunday: Warmer!

Tuesday, March 3, 2015

Winter Front

Now that winter is almost over, a juicy winter storm has hit Utah. Finally! It was fun to watch this storm approach on my way to campus this morning. I managed to walk into the office about 20 minutes before it started snowing. Here's a view out the window of the shelf cloud at the leading edge of the cold front...

Then only a half hour later the winds shifted...

And it's still coming down! Our webcams shows snow has filled the valley.

SunCrest is now socked in with snow. Below is the time lapse video of the front approaching...

You can see the passing of the front in the MesoWest data from the airport station KSLC. It hit the airport just before 8:00 (I was literally 15 minutes ahead of the storm almost to campus.

Then the front hits the William Browning Building just minutes after I walk in (wind data was not showing up, but you still should be able to see the front by the rapid drop in temperature around 8:20).

It took a few hours, but the front eventually reached my station in Spanish Fork at 10:30.

And for my BYU friends, here's from the Eyring Science center, it looks like the front reached you around 10:00 this morning.

And here's the radar...

Looking at the radar and the HRRR model this storm will pass in the next hour or two. Hopefully the roads will be cleared by the evening commute.

Oh, and look at the pretty snowflakes falling at Alta..
source: Alta Snowflake Showcase

Sunday, March 1, 2015

Weather Merit Badge: BYU Pow Wow

Every six months BYU hosts a merit badge pow wow. This is my third time teaching the weather merit badge. Click the picture below for more information. For details about the weather merit badge click here or the picture of the weather merit badge in the right side panel. The website includes

  • class powerpoint
  • requirements worksheet
  • homework instructions
  • web links for weather safety
  • the BSA merit badge pamphlet
  • other fun weather related links

Fort Herriman Junior High visit

Recently I visited several ninth grade classes and talked about what meteorologist do. It was fun to show some weather maps and videos as well as pass around real weather instruments like station sensors and weather balloons. Here is a copy of the powerpoint slides I shared with them...