A closer view of the tornadic supercell is shown below, with overlays of surface reports (metric units). The pulsing nature of the overshooting tops is evident in the fluctuation of the coldest cloud-top IR brightness temperatures (the coldest of which was -69º C, darker black color enhancement, on the 0300 UTC GOES-15 and 0315 UTC GOES-13 images). There are different apparent positions of the storms based on the satellite that views them because of parallax shifts. Such shifts are especially pronounced at higher latitudes with very tall storms.A 1-km resolution Terra MODIS 11.0 µm Infrared image at 0331 UTC is shown below; the minimum cloud-top IR brightness temperature was -73º C. Visible imagery from GOES-13 (above) and GOES-15 (below) showed the overshooting tops associated with the tornadic thunderstorm, as well as the rapidly expanding cirrus shield. A closer view of the tornadic supercell from GOES-15 vs GOES-13 is shown below, with overlays of surface reports (metric units). The overshooting tops are again apparent on the images, along with an above-anvil plume (which is easier seen on the GOES-13 images, due to a more favorable forward-scattering viewing geometry). The robust convective development was first seen on the 2030 UTC images, in the vicinity of the Saskatchewan/Manitoba/North Dakota border region. As an area of low pressure was deepening over eastern Montana, warm and humid air was surging northward into far southern Saskatchewan and Manitoba (surface analyses). GOES sounder derived product images (available from this site) of Convective Available Potential Energy (CAPE), Lifted Index, and Total Precipitable Water (below) showed that the environment across southern Manitoba was becoming increasingly unstable and moist leading up to the time of convective initiation. ]]>
A more detailed view of the fire hot spots was provided by 375-meter resolution (mapped onto a 1-km AWIPS grid) Suomi NPP VIIRS 3.74 µm shortwave IR images (below; click to play animation).Many of the fires were burning in the general vicinity of the Utopia Creek, Indian Mountain airport (station identifier PAIM); a time series of surface observation from that site (below) showed that visibility was 1 mile or less due to smoke at times on 25 July. Daily composites of Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images viewed using the SSEC RealEarth web map server are shown below. ]]>
Meteosat-10 0.8 µm High Resolution Visible images (below; click image to play animation; also available as an MP4 movie file) displayed better detail of the center of the storm circulation when it was immediate off the coast of the Netherlands during the middle of the day.A Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image visualized using the SSEC RealEarth web map server (below) showed the center of the strong mid-latitude cyclone just off the coast of the Netherlands; at the time, winds were gusting to 50 knots at the Amsterdam Schiphol airport. ]]>
Another sequence of GOES-15 visible channel images is shown below (click image to play animation; also available as a MP4 movie file). Another smaller smoke plume can be seen originating from a fire in far southeastern British Columbia.As it continued to burn into the following night; a comparison of Suomi NPP VIIRS 3.74 µm shortwave IR and 0.8 µm Day/Night Band images at 0958 UTC or 3:58 am local time (below) revealed the hot spot (yellow to red to black pixels) and the bright glow of the fire.
—————————————————————————On the following day (22 July), consecutive afternoon (1944 and 2122 UTC) Suomi NPP VIIRS 3.74 µm shortwave IR channel images (above) revealed changes in the shape and areal coverage of the fire hot spot (dark black pixels); the corresponding VIIRS Red/Green/Blue (RGB) true-color images (below) still showed a smoke plume, though is was not as large as that seen on the GOES visible imagery from the previous day.
On 23 July, daytime (1925 and 2104 UTC) Suomi NPP VIIRS 3.74 µm shortwave IR and true-color RGB images (below) continued to display large fire hot spots and a smoke plume drifting toward the east-northeast. The size of the Reynolds Creek Fire was estimated to have increased to 4000 acres.]]>
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.
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.
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.
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.
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 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.
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).
The convection over San Diego produced many lightning strikes on Saturday, as shown on the map below, courtesy of Alex Tardy, NWS San Diego.]]>
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.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. The transport pathway of this smoke feature was rather interesting, as we shall explore with the following sets of images. 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.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. 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. ]]>
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.
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).
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.]]>
GOES-13 sounder Convective Available Potential Energy (CAPE) derived product images (above; click to play animation) showed a large cluster of of severe thunderstorms that developed in eastern Kansas and moved southeastward across southern Missouri into northern Arkansas during the day on 14 July 2015. Due to strong surface heating and ample low-level moisture ahead of the storms, the atmosphere became quite unstable with GOES sounder CAPE values reaching the 5800-6000 J/kg range (lighter violet color enhancement) by 16 UTC. A long swath of damaging winds (SPC storm reports) was produced by these storms.
The visible and infrared images below show snapshots of this severe convective cluster at 3 different times, using high-resolution data from instruments on polar-orbiting satellites: Terra MODIS at 1657 UTC, Suomi NPP VIIRS at 1851 UTC, and POES AVHRR at 1916 UTC. The coldest cloud-top IR brightness temperatures were -83º C on the MODIS image, -86º C on the VIIRS image, and -87º C on the AVHRR image.]]>
Himawari-8 10.35 µm infrared imagery showed an unusual (for infrared imagery) double-eyewall structure in Typhoon Nangka over the western Pacific Ocean on 13 July 2015. For such a feature to appear in infrared imagery, the secondary circulations of both the inner and outer eyewall need to be intense enough to support the downdraft/cloud-clearing necessary to create the “moats” between them. Microwave imagery of the storm, below, viewed via MIMIC (from this site), also showed the double eyewall structure quite well. This double-eyewall signature typically indicates that a tropical cyclone is experiencing an eyewall replacement cycle (ERC), which signals that a (temporary) decrease in intensity is soon to follow.
Several hours later, a DMSP SSMIS 85 GHz microwave image at 1756 UTC, below, indicated that the ERC was essentially complete. Subsequently, the Joint Typhoon Warning Center slightly downgraded the intensity of Typhoon Nangka for their 21 UTC advisory. While not as well-defined as in the Himawari-8 imagery, the double-eyewall signature was still evident in the lower-resolution (4-km, vs 2-km) MTSAT-2 IR imagery (animation).
The Himawari-8 Target Sector was centered over Typhoon Nangka during this time; an IR image animation with a 2.5-minute timestep, below (courtesy of William Straka, SSEC), showed the evolution of the double eyewall signature, along with 2 pulses of storm-top gravity waves which propagated radially outward away from the center in the northern semicircle of the typhoon.]]>