Stories tagged CIMSS


I visited to Fort Collins to help celebrate the 50th anniversary of the CSU Department of Atmospheric Sciences. A great celebration and an opportunity to see colleagues I haven't seen in many years.

On Saturday I drove through a section of the Cache La Poudre River to see some of the burnt scares from the High Park fire. The fire started on June 9 by a lightning strike and burned across 87,284 acres by early July, taking 259 homes. One person has died in the fire. It is the second-largest fire in Colorado's history and has cost about $30 million to fightHigh Park Fire impact on the Cache La Poudre River: A view of the Cache La Poudre River on July 14, 2012
High Park Fire impact on the Cache La Poudre River: A view of the Cache La Poudre River on July 14, 2012Courtesy Steve Ackerman

A recent rain washed the ash into the river, which now runs gun-powder black, as you can see in the photo. This is black color is consistent with the name Cache La Poudre. I have to wonder how this sediment will impact the fish in the water. This is an excellent river for trout.

Notice the burnt trees along the ridge line in the photo. Also notice the dead pine trees in the photo; a result of the pine beetle. The mountain pine beetles inhabit ponderosa, lodgepole, Scotch and limber pine trees and play an important role in the life of a forest. The black beetle attacks old or weakened trees which helps development of a younger forest. However, unusual hot, dry summers and mild winters have led to an epidemic. It would seem logical that these beetle damaged trees would increase fire risks as dead trees are flammable and likely to catch fire. But this might not be the case, indeed the dead trees may inhibit the spread of fires. The Yellowstone wildfire of 1988 provided forest ecologists with a method. Large crown fires can swept quickly through the forest spreading from tree tops. In the 1988 fire there were many trees killed and their needles burned off, but the standing dead tree trunks remained. New wildfires tend to slow and sometimes burn out when they reach standing dead forest. An interesting research topic!


The June 29, 2012 derecho swept across from US from west of Chicago to the East Coast, leaving as many as 5 million households without power. The storm traveled at speeds of over 60 mph, with wind gusts approaching 80 mph. At least 22 people were killed.

A derecho (pronounced deh-RAY-cho, a Spanish word meaning “straight ahead”) is an hours-long windstorm associated with a line of severe thunderstorms. It is a result of straight-line winds, not the rotary winds of a tornado—hence its name. Derechos in the United States are most common in the late spring and summer (May through August).
Derecho climatology: The number of derecho windstorms occurring from 1994 to 2003 across the United States.
Derecho climatology: The number of derecho windstorms occurring from 1994 to 2003 across the United States.Courtesy Ackerman &amp; Knox: Meteorology: Understanding the Atmosphere

The extreme winds of a derecho—up to 150 mph in the strongest storms—come about in the following way. Derechos are often associated with a quasi-stationary front in mid-summer. If the atmosphere just north of the front is very unstable, the front may trigger rapidly developing thunderstorms. A line of thunderstorms that forms in the vicinity of the stationary front can, via its cold downdrafts, drag down high-speed air from above. This can cause the high winds of a derecho.

At the same time, the high winds push the line of thunderstorms outward, causing it to bend or “bow.” This results in a bow echo image on weather radar. Once they get going, derechos can cover lots of territory—up to 1000 miles—and leave significant property damage in their wake, even flattening entire forests. In some cases, derechos wreak as much havoc as a hurricane or tornado. About 40% of all thunderstorm-related injuries and deaths occur because of derechos.


Tornadoes form in regions of the atmosphere that have abundant warm and moist air near the surface with drier air above, a change in wind speed and direction with height, and weather systems such as fronts that force air upward. The United States provides these three ingredients in abundance, so it is not surprising that the majority of the world’s reported tornadoes occur in the USA. Within the United States, tornadoes can occur in nearly every state and in every month of the year. Wisconsin has experienced tornadoes in every month except February. It is generally accepted that tornado season begins in the springtime— and that is now.

Tornado season is based on when the ingredients for severe weather come together in a particular place. Because a change in wind with height is closely related to the presence of a jet stream, tornado season moves north and south during the year with a jet stream. Tornado season peaks in March and April in the Southeast but not until July in the upper Midwest and Northeast. The deep South has a secondary peak in tornado occurrence in November.
Month of maximum tornado threat: The geographic distribution of the month of maximum tornado threat for the continental United States.
Month of maximum tornado threat: The geographic distribution of the month of maximum tornado threat for the continental United States.Courtesy Ackerman &amp; Knox: Meteorology: Understanding the Atmosphere

Tornadoes can also happen at any time of day or night. However, they thrive on solar heating and in some cases the ability of warm, moist air at the surface to penetrate the capping inversion. Therefore, the most likely times for tornadoes are late afternoon or early evening. More than half of all U.S. tornadoes occur during the hours of 3:00 PM to 7:00 PM local time.


Thailand Flooding from Space
From the NASA Image of the Day on October 28:








The entire nation now has a new ‘normal temperature.’ These climatological temperatures, and other weather parameters, are computed by averaging all temperatures over a 30-year period. These averages are called normal temperatures. These averages serve as a reference point and are used to help us interpret average climate conditions at a particular location. A comparison of today’s temperature with the normal temperature helps us determine if today is an atypical weather day. Private industry also uses these temperatures in the planning. For example, energy companies use the normal temperature for long term planning of energy usage. Agriculture uses this as they monitor a particular growing season.

The National Ocean and Atmosphere Administration’s National Climatic Data Center (or NCDC) calculates the normal weather conditions over a thirty year period for more than 7,500 locations in the United States.
Since this time period is a reference point, we have to define the 30-year period. As of July 1, this averaging period is 1981-2010. Prior to that date, the averaging period was 1971-2000. So, what does this new period tell us?

The normal temperature for the entire US is about 0.5 °F warmer now than it was during the 1971-2000 time period. The normal low temperature for WI is about 0.8 °F warmer now than it was in the 1971-2000 period; and WI normal high temperature is about 0.6 °F warmer. According to Assistant State Climatologist of WI, Dr. E. Hopkins, the new normal high and low temperatures for Madison (which is where I live) are 56.6 and 36.7, which are 0.2 and 1.2 degrees higher than the previous 30-year period.

You can find the new normals for where you live at this site:








A number of severe thunderstorms have swept through the SE US recently. Some storms generated tornadoes that were truly devastating. The news channels have many photos of the ground destruction. We can see the path of the storms in satellite images. Here is a link to one of those images.

A comparison of 250-meter resolution image from a NASA MODIS instrument at 0.65 µm and 0.87 µm visible channel images centered on Tuscaloosa, Alabama on 28 April 2011 showed signatures of a few of the larger and longer tornado damage paths from the historic tornado outbreak (SPC storm reports) that occurred on 27 April 2011. The yellow arrows point to some of the paths.

Here is a link to an animation between the two channelsMODIS Image of Tornado Paths on 28 April 2011: NASA Satellite image see tornado path
MODIS Image of Tornado Paths on 28 April 2011: NASA Satellite image see tornado pathCourtesy CIMSS UW-Madison


We have heard about the many fires in Russia. NASA satellites have detected over 600 600 hotspots from wildfires within Russian territory in one day!

Fires produce a heat signature that is detectable by satellites even when the fires represent a small fraction of the pixel. Fires produce a stronger signal in the mid-wave IR bands (around 4 microns) than they do in the long wave IR bands (such as 11 microns). That differential response forms the basis for most algorithms that detect the presences of a fire, the size of the fire, the instantaneous fire temperature.

The unusually hot and dry mid-August conditions beneath a strong ridge of high pressure across British Columbia led to a major outbreak of wildfires across that western Canadian province. The satellite image shows the location of those fires as red squares. The smoke plumes are also seen on the satellite imagery.

Here's an image from a NASA instrument: The red squares are fire locations and the smoke from the fires is evident.

The aerosols released by fires and the degraded air quality caused by them represent tremendous costs to society, so reliable information on fire locations and characteristics is important to a wide variety of users. For this reason, NOAA tracks these plumes and makes them publically available from NOAA at: