NWS Reno: Forecasting for the Sierra and Western Nevada Since 1905

Western Pacific typhoons are not always just a curious side note. In fact, they can affect the storm pattern over our region significantly, especially in the fall and winter. If a tropical system over the western Pacific gets absorbed into the storm flow at the right location, it can amplify/energize the pattern, potentially leading to stronger storms over North America. Check out the video** below, which shows  a typhoon (red symbol) just before absorption followed by the movement of the energy (shaded area) downstream after the typhoon is ingested into the flow. Notice how the flow (indicated by white lines) amplifies as the former typhoon energy moves across the Pacific and into Canada and the United States. Amplified flow can bring about a significant clash of air masses (cold Canadian and subtropical) and initiate the development of powerful winter storms. Computer models often have trouble predicting how exactly tropical systems will be absorbed into the flow, which unt...

On the evening of Sunday September 27th (mainly between 7 and 8:30 pm), we will be able to view an astronomical treat that hasn't happened in over 30 years! There will be a combination of a supermoon (perigree full moon) along with a total lunar eclipse! So what exactly is a supermoon? It's a new or full moon closely occurring with perigree - the moon's closest point to Earth in its orbit. This particular supermoon will be the closest supermoon of the year (other full moon supermoons this year: August 29th and October 27th) being only 221,754 miles away from Earth. About three or four times a year (in the spring and the fall), the new or full moon coincides closely in time with the perigree of the moon - the point when the moon is closest to the Earth. Image Courtesy NOAA Like I mentioned earlier, this September supermoon will be a treat because it will coincide with a total lunar eclipse! Check out this great animated video by NASA's Goddard Space Flight Center ...

Let's take a look back at Summer 2015. Although astronomical fall hasn't begun, meteorological summer has ended. What? There is a bit of a difference between the two. Astronomical summer ends (or fall begins) when the Autumnal Equinox occurs, around September 22-23 ( specifically September 23, 2015 at 8:20 UTC in the northern hemisphere ) So why would meteorological summer end (or fall begin) at a different time? It's basically because the astronomical seasons are based on the Earth's position related to the Sun while the meteorological seasons are based on the temperature cycles through the year. For a more in depth discussion on what the difference is between the two, check out this great write-up by NOAA's NCEI (National Centers for Environmental Information).  Anyways, back to the Summer summary for Reno. Looking back at the summer, we had a VERY active monsoon pattern which resulted in multiple days of thunderstorms and flooding for the Sierra and weste...

Well the smoke has returned... it seems like an appropriate time to have Washoe County Air Quality guest blog about the smoke again. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -      Wildfire smoke contains many different pollutants with fine particulates (PM2.5) being the most concerning (see blog post "Wildfire Smoke in Northern Nevada ). The Washoe County Air Quality Managament Division's PM2.5 monitoring network has been monitoring since 1999. In addition to the two permanent PM2.5 monitors at our Reno3 and Sparks monitoring sites, we recently deployed portable beta attenuation monitor (E-BAM) for PM2.5 monitoring at Pleasant Valley Elementary to expand our network during wildfire season (see map). An E-BAM's purpose is to get accurate PM2.5 data so that the public can make health based decisions as soon as possible. Decisions like keeping windows closed at night, having recess or practice indoors, and cancelling events like a triathlon ar...

El Niño and La Niña are weather catch phrases that are thrown around pretty frequently, but how many of us truly know what these features are? They are complex atmospheric-oceanic circulations, and to be honest, it's more than we could even explain in a short blog post, but we will cover some of the basics here. Let's start with El Niño since we currently have these conditions in place. El Niño is the warm phase of the El Niño Southern Oscillation (ENSO) and refers to warming in the equatorial Pacific sea surface temperatures (SSTs) compared to normal. Here is a quick video explaining this phenomenon: La Niña is the cool phase of ENSO and refers to cooling in the equatorial Pacific SSTs compared to normal. One more quick video to explain: The strength of El Niño and La Niña episodes is determined by the difference in SSTs compared to normal and are measured in a region of the east-central Pacific Ocean known as the Niño 3.4 Region: The Oceanic Niño Index (...

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...

Enjoy this guest post from our friends at Washoe County Air Quality !  - - - - - - - - Forecast calls for sunny skies and hot temperatures for Northern Nevada. The air quality should be good as long as there isn't any wildfire smoke, right? Well, not necessarily. Let me explain.  Summer is the season of ozone (O 3 ). There is both stratospheric and ground level O 3 . The stratospheric ozone protects us from the Sun's harmful ultraviolet radiation. Ground level ozone is an air pollutant that harms humans and the environment especially during hot and sunny summer afternoons.  Ground level O 3  is created by the chemical reactions between volatile organic compounds (VOCs) and oxides of Nitrogen (NO x ) in the presence of sunlight. NOx and VOCs, also ozone precursors, come from motor vehicles, industrial processes, power generation, and consumer products among many other things including wildfire smoke. Urban and suburban areas will have higher leve...