Smoke and Radar: American Fire Smoke engulfs Reno 2 years ago today.


Everyone is familiar with weather radar and how it can detect areas of precipitation, but radar is also an indispensable tool when it comes to helping identify storms which have the potential to become severe. Normally when we refer to severe storms in the West, we are referring to storms that are capable of producing damaging winds/hail and also flash flooding. Here in the Sierra and western Nevada, tornadoes are fairly uncommon but still can happen as was the case this past June in Hawthorne, NV where an EF-1 tornado formed. 
Smoke on Satellite

  The satellite image below (fig 1) shows a true color view from the afternoon of the 8/18/13. What is notable is the smoke plume from the American Fire hovering over the Sierra west of Lake Tahoe. The next image later that afternoon (fig 2) show thunderstorms had formed across the Sierra south of Tahoe while smoke had begun to travel up slope of the Sierra. 
Figure 1: MODIS-Terra satellite image from the afternoon of 8/18/13.
Wildfire smoke can be seen along the west slopes of the Sierra.
Figure 2: MODIS-Aqua satellite image later that afternoon.
Thunderstorms can be seen developing along the Sierra south of Lake Tahoe.
Smoke from the fire can be seen travelling up the Sierra
near the developing clouds and storms. 
Smoke on Radar


Thunderstorms continued to develop across the Tahoe Basin and clouds began to hide the view of the smoke from satellite imagery. How do you then track the movement of smoke when clouds are hiding them from view on satellite???  That's where radar came into play that day.  Although it is not always possible, the smoke plume was able to be detected by radar that day as it was located at an elevation and distance within sight of the radar. 


The image below shows (fig 3) shows an outflow wind boundary from a thunderstorm that was traveling east over the Carson Range and towards Reno. The big question was: Is this outflow going to bring smoke with it?  Without webcams or spotter reports to provide the answer, we turned to our radar.  


outflow.JPG
Figure 3: Thunderstorm outflow boundary pushing eastward towards Reno.


The radar loop below shows this north-south oriented outflow boundary pushing cross the Carson Range.  The WSR-88D radar sitting on top of Virginia Peak received an upgrade to include Dual-Polarization technology (or Dual Pol for short) back in 2012.  One of dual-pol’s benefits is that it’s able to distinguish not just where precipitation is but what type it likely is (hail, snow rain) and even if it's not precipitation at all (insects, birds, dust, smoke).





The loop below shows one of those complex dual-pol products called Differential Reflectivity. Basically with dual-pol, the radar can now send out a vertical and horizontal radar pulse, in the process it can get a rough idea on the orientation and what the shape of the detected object might be. In this case, the radar was detecting something that wasn’t rainfall but most likely was detecting the smoke being caught up in the outflow boundary. 




A few minutes later suspicions were confirmed as the wall of smoke became visible over the top of the Carson Range. (fig 4)

smokeCarson.JPG
Figure 4: Once this boundary pushed over the Carson Range, the wall of smoke 
became visible from the NWS office.


This wall of smoke rapidly descended down into Reno in about 30 minutes and resulted in a rapid deterioration of air quality and visibility. Dual-pol radar proved extremely useful in getting an early alert of the possible smoke threat and we were able to get the word out with short-term products and social media about the oncoming smoke! We managed to capture a timelapse of the smoke descending the mountains and completely engulfing Reno. The 9 second time lapse that afternoon runs from 5:20pm-6:00pm.




Below are a few links to our social media outlets and also some air quality sites that we find quite useful year-round. Thanks for reading!

Bureau of Air Quality Planning: http://nvair.ndep.nv.gov/ UNR PM2.5 Sensor: http://www.patarnott.com/pas532/ Map of Particulate Sensors: http://smoke.airfire.org/monitoring/#/ NWS Reno Social Media: NWS Facebook: https://www.facebook.com/NWSReno NWS Twitter: https://twitter.com/nwsreno NWS YouTube: https://www.youtube.com/user/NWSReno







Popular posts from this blog

NWS Wind Forecasts: AKA What's the Deal With Friction?

Image
We have had a number of comments on social media which mention much lower observed wind speeds locally than are in the forecast. Well, you are unlikely to know this (it is not exactly advertised!) but National Weather Service wind forecasts are for 10 meters, or almost 33 ft, above the ground. As we are about to explain, that makes all the difference in the wind between eye-level (~5-6 feet) and ~33 feet.  It is natural to wonder the purpose of a wind height forecast well above where you and I typically reside. The main reason for this is the complication in forecasting wind as one nears the ground due to frictional influence caused by the surface. Here is a diagram showing the concept of wind speeds change as one gets away from the ground.  As you can see above, there is a rapid speed reduction (gray dashed line) near the ground with a lesser change away from the surface. Note that the above diagram is generalized. How much reduction is realized depends on the nature of the s...
Read more

What is the Rain Shadow and What's Wind Gotta do With It?

Image
The dreaded rain shadow - something that those of us who live east of the Sierra crest are more than familiar with and hate to hear. So what is this rain shadow and why does it even exist? Lets start with the topography just to our west... The Sierra Nevada mountain range runs 400 miles from north-to-south and is approximately 70 miles wide. It includes the highest peak in the lower 48, Mt Whitney at 14,505 feet, and rises above 10,000 feet in many locations. Left: The Sierra Nevada Mountains highlighted in blue. Right: A relief map showing elevation (in meters) of the Sierra. The Sierra are a significant barrier for Pacific storms which typically move from west to east. The movement of air masses and associated weather cannot go through the mountains and is forced up and over the mountain range. As Pacific moisture is driven eastward by the wind, the air mass is lifted up and over the Sierra. Rising air will cool and once it reaches the point of saturation, condense into...
Read more

Forecasting "Dry Microburst" Potential From Soundings and Observations

Image
Summer afternoons in the valleys of eastern California and western Nevada usually feature dry low level relative humidity. In certain cases where low levels are very dry (single digit relative humidities) and enough instability for showers and/or thunderstorms exists, there is the heightened possibility for severe (over 60 mph) outflow winds. Now, severe winds are possible from strong thunderstorms in many cases, even without very dry surface relative humidity. However, what makes very dry surface or low level conditions special is that severe outflow winds are possible even with w eak  convection such as light showers...or even just cumulus clouds! When severe winds are produced by convection with little or no rainfall reaching the ground, it is referred to as a "dry microburst". Microbursts can be of significant danger to aviation and, if they are strong enough, life and property. Before we move onto what conditions we look for to determine the threat for dry microbursts,...
Read more