How long can Tornado Scars last?

July 22nd, 2015
MODIS True-Color Image,  June 9, 2007 (left) and  July 15, 2015 (right) (click to enlarge)

MODIS True-Color Image, June 9, 2007 (left) and July 15, 2015 (right) (click to enlarge)

On 07 June 2007, severe thunderstorms moved through the Upper Midwest (blog post on that event), spawning strong tornadoes; from the SPC Storm Reports comments:

HUNDREDS OF TREES DOWN NORTH OF ZOAR. (GRB)

NUMEROUS TREES DOWN OF 1 FOOT DIAMETER AND GREATER. TRACK WAS APPROXIMATELY 1/4 MILE IN LENGTH AND 125 YARDS WIDE (MQT)

Terra MODIS data on 09 June 2007 (in the image above, at left) showed a tornado scar (much longer than 1/4 mile in length) running southwest-to-northeast through heavily forested Menominee County into Langlade County and then Oconto County in northeast Wisconsin. Terra MODIS True-Color imagery from 15 July 2015 (also in the image above, at right) (cropped from imagery at the MODIS Today website), shows that a scar persists more than 8 years later! (This persistent scar has been mentioned before on this blog here in 2009 and here in 2011).

Landsat-8 overflew northeast Wisconsin on 15 July 2015, at nearly the same time as the Terra MODIS imagery above, and those views, captured via SSEC‘s RealEarth are shown below. The scar is more evident in the shortwave infrared (Band 6, 1.61 µm) than the visible (Band 3, 0.56 µm) because the shortwave infrared channel is more sensitive to changes in vegetation. Lakes are also far more apparent in the 1.61 µm imagery because water absorbs 1.61 µm radiation; little is scattered back to the satellite for detection and water therefore appears black.

Landsat-8 band 3 (0.56 µm) and Band 6 (1.61 µm) imagery, ~1640 UTC July 15, 2015 (click to enlarge)

Landsat-8 band 3 and Band 6 imagery, ~1640 UTC July 15, 2015 (click to enlarge)


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In April 2011, an historic tornadic event occurred over the Deep South that spawned numerous strong long-tracked tornadoes (blog post). The tornado paths from this event were also visible from both MODIS and GOES imagery (Link). The animation below shows MODIS true color imagery from before the tornadoes, from several days after, and from early May this year. Three distinct tornado scars remain in Alabama: One runs from Tuscaloosa to Birmingham, a second is south of Tuscaloosa, and a third is north of Tuscaloosa.

MODIS True-Color Imagery over Alabama, 13 April and 29 April in 2011 and 01 May in 2015 (click to enlarge)

MODIS True-Color Imagery over Alabama, 13 April and 29 April in 2011 and 01 May in 2015 (click to enlarge)

Flooding Rains in southern California

July 20th, 2015
GOES-15 Infrared Water Vapor (6.5 µm) Images  (click to play animation)

GOES-15 Infrared Water Vapor (6.5 µm) Images (click to play animation)

Unusual rains causing flooding and mudslides hit southern California (San Diego in particular) on 18-19 July 2015. The two-day rain total (1.69″) at Lindbergh Field broke the monthly record for July (previous record, 1.29″) and exceeded the January-April 2015 rainfall (the typical wet season) at the station. The San Diego Padres had their first July rainout ever, and the Anaheim Angels had their first rainout since 1995! What caused the rains? The water vapor imagery, above, shows the three systems that contributed. Pacific Hurricane Dolores (Track) was declared post-tropical off the coast of Baja California at 0300 UTC on 19 July. Farther to the west, Pacific Tropical Storm Enrique was declared post-tropical at 0300 on 18 July. High pressure aloft was helping support a Gulf Surge, a surge of moisture up the Gulf of California towards the desert southwest. Two animations of MIMIC Total Precipitable Water, below, show the surge and also show that moisture associated with main circulation of Dolores remains mostly offshore until late on the 19th, after the heavy rains had ended.

MIMIC Total Precipitable Water, 0000 UTC on 15 July through 0000 UTC on 18 July 2015 (click to enlarge)

MIMIC Total Precipitable Water, 0000 UTC on 15 July through 0000 UTC on 18 July 2015 (click to enlarge)

MIMIC Total Precipitable Water, 0000 UTC on 18 July through 0000 UTC on 21 July 2015  (click to enlarge)

MIMIC Total Precipitable Water, 0000 UTC on 18 July through 0000 UTC on 21 July 2015 (click to enlarge)

The Blended Precipitable Water Product (data collected from this site), below, also shows evidence of a Gulf Surge of moisture moving northward through the Gulf of California in the few days preceding the rains.

NESDIS Blended Total Precipitable Water (left) and Percent of Normal (right), 1200 UTC on 15 July through 1200 UTC on 20 July 2015 (click to animate)

NESDIS Blended Total Precipitable Water (left) and Percent of Normal (right), 1200 UTC on 15 July through 1200 UTC on 20 July 2015 (click to animate)

The animation of 10.7 µm imagery, below, suggests that the precipitation on Saturday the 18th was associated more with the Gulf Surge of moisture (which surge was likely influenced both by the large scale synoptic flow and by the circulation of Dolores); precipitation on Sunday the 19th seems more directly influenced by Dolores.

GOES-15 Infrared (10.7 µm) Images  (click to play animation)

GOES-15 Infrared (10.7 µm) Images (click to play animation)

What part did the upper-level outflow jets from the two tropical cyclones play in this event? Consider the water vapor animation below, zoomed in from the larger-scale view at the top of this post. Outflow from Enrique moves from the southwest part of the domain towards the southern California coast (the low-level circulation of Enrique are at the southwest edge of the domain), moving inland as convection develops on Saturday 18 July 2015. The Total Precipitable Water imagery suggests that convection starts as the leading edge of the Gulf Surge arrives; water vapor imagery suggests a tie to Enrique.

GOES-15 Infrared Water Vapor (6.5 µm) Images  (click to play animation)

GOES-15 Infrared Water Vapor (6.5 µm) Images (click to play animation)

GOES-15 Visible Imagery, below, from Saturday the 18th and from Saturday the 19th suggest rain on 19 July was more directly tied to the circulation of Dolores. On both days, the convective nature of the precipitation is apparent, with numerous overshooting tops present. Convection on Sunday the 19th started over higher terrain first, and then was joined by tropical convection moving in from the ocean.

GOES-15 Visible (0.65 µm) Images, 1300 UTC 18 July through 0300 UTC 19 July 2015  (click to play animation)

GOES-15 Visible (0.65 µm) Images (click to play animation)

GOES-15 Visible (0.65 µm) Images, 1300 UTC 19 July through 0300 UTC 20 July 2015  (click to play animation)

GOES-15 Visible (0.65 µm) Images (click to play animation)

As might be expected, the San Diego sounding (source) shows deep tropical moisture late on the 18th and late on the 19th as the heavy rains occurred. The precipitable water value of 2.10″ at 0000 UTC on 20 July was a top 5 value for July (Source). The rains caused two spikes in the flow of the San Diego River (Link, courtesy Alex Tardy, NWS San Diego).

Stuve plots of radiosonde data at 72293, 0000 and 1200 UTC 19 July and 0000 UTC 20 July 2015  (click to enlarge)

Stuve plots of radiosonde data at 72293, 0000 and 1200 UTC 19 July and 0000 UTC 20 July 2015 (click to enlarge)

The convection over San Diego produced many lightning strikes on Saturday, as shown on the map below, courtesy of Alex Tardy, NWS San Diego.

Lightning Strikes for the 24 hours ending 2 PM PDT on Saturday 18 July 2015 (click to enlarge)

Lightning Strikes for the 24 hours ending 2 PM PDT on Saturday 18 July 2015 (click to enlarge)

Wildfire smoke: from Alaska to Norway, via the Arctic and Atlantic Oceans

July 18th, 2015

Meteosat-10 0.8 µm visible channel images [click to play animation]

Meteosat-10 0.8 µm visible channel images [click to play animation]

EUMETSAT Meteosat-10 High Resolution Visible (0.8 µm) images (above; click to play animation; also available as an MP4 movie file) revealed the hazy signature of what appeared to be a ribbon of smoke aloft being transported eastward across the North Atlantic Ocean by the circulation of a large area of low pressure (surface | 500 hPa) on 17 July 2015. Early in the day, the smoke feature stretched from the east coast of Greenland to the central Atlantic Ocean; by the end of the day, the leading edge of the smoke had moved over the British Isles and was headed toward Scandinavia.

A portion of the smoke plume could be seen on Aqua MODIS and Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images (below) as it was approaching the southern portion of Great Britain.

Aqua MODIS and Suomi NPP VIIRS true-color images [click to enlarge]

Aqua MODIS and Suomi NPP VIIRS true-color images [click to enlarge]

On the following morning, Meteosat-10 visible images (below; click to play animation) showed that the leading edge of the smoke ribbon was moving over southern Norway.

Meteosat-10 0.8 µm visible channel images [click to play animation]

Meteosat-10 0.8 µm visible channel images [click to play animation]

The transport pathway of this smoke feature was rather interesting, as we shall explore with the following sets of images.

Suomi NPP VIIIRS 3.74 µm shortwave IR and 0.64 µm visible images on 06 July [click to enlarge]

Suomi NPP VIIIRS 3.74 µm shortwave IR and 0.64 µm visible images on 06 July [click to enlarge]

The 2015 wildfire season in Alaska had been very active — as of 17 July, it was rated as the 4th worst in terms of total acreage burned. In early July, numerous wildfires burning across the interior of Alaska were producing a large amount of smoke, as can be seen in a comparison of of Suomi NPP VIIRS 3.74 µm shortwave IR and 0.64 µm visible channel images at 2131 and 2312 UTC on 06 July (above). The thermal signature of the wildfire “hot spots” showed up as yellow to red to black pixels on the 2 shortwave IR images, while the widespread smoke plumes from the fires are evident on the 2 visible images; even in the relatively short 101 minutes separating the two sets of VIIRS images, notable changes in fire activity could be seen.

Looking a bit farther to the north and west, a sequence of VIIRS 0.64 µm visible images centered over Cape Lisburne (station identifier PALU) in northwestern Alaska covering a 2-day period from 06 to 08 July (below) showed the initial transport of large amounts of smoke from the interior of Alaska northwestward over the Chukchi Sea between Alaska and Russia.

Suomi NPP VIIRS 0.64 µm visible channel images covering the 06-08 July period [click to enlarge]

Suomi NPP VIIRS 0.64 µm visible channel images covering the 06-08 July period [click to enlarge]

Daily composites of Suomi NPP OMPS Aerosol Index covering the period of 04-17 July (below; courtesy of Colin Seftor; see his OMPS Blog post) showed the strong signal of this dense Alaskan smoke (denoted by the red arrows) as it moved from east to west over the far southern Arctic Ocean and along the far northern coast of Russia from 06-10 July. The Aerosol Index signal seemed to stall north of Scandinavia on 12-13 July, but then a small portion began to move toward Iceland and Greenland on 13-15 July around the periphery of a large upper-level low (500 hPa analyses). Finally, some of this smoke was then transported eastward across the Atlantic Ocean around the southern periphery of this upper-level low on 17 July, as was seen on the Meteosat-10 visible images at the beginning of this blog post.

Suomi NPP OMPS Aerosol Index images, covering the period 04-17 July [click to enlarge]

Suomi NPP OMPS Aerosol Index images, covering the period 04-17 July [click to enlarge]

CALIOP lidar data from the CALIPSO satellite (below) showed the vertical distribution of the Alaskan smoke over and off the coast of northern Norway on 11 July. The signal of the smoke was located in the center portion of the images; while there appeared to be some smoke at various altitudes within the middle to upper troposphere, a significant amount of smoke was seen in the lower stratosphere in the 10-12 km altitude range.

CALIPSO CALIOP lidar data showing the smoke over northern Norway on 11 July [click to enlarge]

CALIPSO CALIOP lidar data showing the smoke over northern Norway on 11 July [click to enlarge]

Wildfires in Greece

July 17th, 2015
Suomi NPP VIIRS true-color image (actual satellite overpass time 1112 UTC)

Suomi NPP VIIRS true-color image (actual satellite overpass time 1112 UTC)

Suomi NPP VIIRS (above; toggle with Google maps) and Aqua MODIS (below; toggle with Google maps) true-color Red/Green/Blue (RGB) images visualized using SSEC RealEarth showed 2 smoke plumes from wildfires burning in Greece on 17 July 2015. These fires were causing evacuations in some areas, according to the Wildfire Today site.

Aqua MODIS true-color image composite (actual satellite overpass times 1102 UTC and 1240 UTC)

Aqua MODIS true-color image composite (actual satellite overpass times 1102 UTC and 1240 UTC)

Surface observations around the time of the images (below) indicated that air temperatures were in the 90-100º F (32.2-37.8º C) range at many sites across the region. Winds at Athens were from the northeast at 26 knots, with gusts to 36 knots (time series plot of surface data). Near the edge of the larger smoke plume to the southwest, the surface visibility was restricted to 5 miles at Kithira (but was as low as 3 miles at 10 UTC: time series plot of surface data).

Aqua MODIS true-color image, with Athens, Greece surface observation (click to enlarge)

Aqua MODIS true-color image, with Athens, Greece surface observation (click to enlarge)

Aqua MODIS true-color image, with Kithira, Greece surface observation (click to enlarge)

Aqua MODIS true-color image, with Kithira, Greece surface observation (click to enlarge)

EUMETSAT Meteosat-10 High Resolution Visible (0.8 µm) and shortwave IR (3.92 µm) images (below; click to play animation; also available as an MP4 movie file) showed thee temporal evolution of the smoke plume and the associated fire hot spots (dark black to red pixels). Athens is located within the cyan circle on the images.

Meteosat-10 visible and shortwave IR images (click to play animation)

Meteosat-10 visible and shortwave IR images (click to play animation)