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Tornado at Denver International Airport

June 18th, 2013

Suomi NPP VIIRS 0.64 um visible image and 11.45 um IR channel image (with overlay of METAR surface reports)

A tornado touched down just east of the Denver International Airport concourses at 20:21 UTC on 18 June 2013, producing a peak wind gust of 97 mph (before the wind instrumentation stopped transmitting data). AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel data at 20:03 UTC (above) showed the storm about 20 minutes before it produced the tornado. The minimum cloud-top IR brightness temperature was -68º C (darker red color enhancement), which was significantly colder that the tropopause temperature of -56º C on the 12 UTC Denver rawinsonde data.

The corresponding Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image (viewed using the SSEC Web Map Server) is shown below.

Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image

The series of METAR surface reports from Denver (KDEN) during the period from 20:20 to 20:37 UTC:

KDEN 182037Z 09026KT 9SM -TSRA FEW050 BKN080CB BKN180 24/04 A3002 RMK FUNNEL CLOUD B18 FUNNEL CLOUD E20 TORNADO B21 TORNADO E36 AO2 LTG DSNT NE-S RAB03 TORNADO 2 SE MOV N P0005
KDEN 182032Z 09026KT 7SM +FC -TSRA FEW050 BKN080CB BKN180 22/08 A3001 RMK FUNNEL CLOUD B18 FUNNEL CLOUD E20 TORNADO B21 AO2 LTG DSNT NE-S RAB03 TORNADO 2 SE MOV N P0005
KDEN 182022Z 06021G28KT 5SM +FC TSRA FEW050 BKN080CB BKN180 21/07 A3002 RMK FUNNEL CLOUD B18 FUNNEL CLOUD E20 TORNADO B21 AO2 PK WND 07028/2020 LTG DSNT E-S RAB03 OCNL LTGICCG VC E TS OHD MOV E VIRGA SW P0005
KDEN 182021Z 06022G28KT 5SM +FC TSRA FEW050 BKN080CB BKN180 21/06 A3003 RMK FUNNEL CLOUD B18 FUNNEL CLOUD E20 TORNADO B21 AO2 PK WND 07028/2020 LTG DSNT E-S RAB03 OCNL LTGICCG VC E TS OHD MOV E VIRGA SW P0005
KDEN 182020Z 07020G28KT 5SM FC +TSRA FEW050 BKN080CB BKN180 21/07 A3003 RMK FUNNEL CLOUD B18 AO2 PK WND 07028/2020 LTG DSNT E-S RAB03 OCNL LTGICCG VC E TS OHD MOV E VIRGA SW P000

McIDAS images of GOES-13 0.63 µm visible channel data (below; click image to play animation) showed the development of the thunderstorms over the region

GOES-15 0.63 µm visible channel images (click image to play animation)

Posted in GOES-15, Red/Green/Blue (RGB) images, Severe convection, Suomi NPP, VIIRS, Web Map Server | No Comments »

Severe weather in the Oklahoma City area

May 31st, 2013

GOES-14 sounder Convective Available Potential Energy (CAPE) product (click image to play animation)

Only 11 days after the devastating EF-5 tornado that struck Moore, Oklahoma, another round of severe weather brought tornadoes (including the EF-5 El Reno tornado) large hail (up to 2.5 inches in diameter), damaging winds (gusts as high as 87 mph), and heavy rain that led to flash flooding to the Oklahoma City area on 31 May 2013 (SPC storm reports| NWS Norman summary). AWIPS images of the 10-km resolution GOES-14 sounder Convective Available Potential Energy (CAPE) derived product (above; click image to play animation) showed the trend of rapid destabilization across the region during the hours leading up to convective initiation — widespread CAPE values in the 5000-6000 J/kg range were seen (lighter purple color enhancement).

Once convective initiation began the storm growth was explosive, as revealed by McIDAS images of 1-km resolution GOES-14 0.63 µm visible channel data (below; click image to play animation; also available as a QuickTime movie). The GOES-14 satellite had been placed into Rapid Scan Operations (RSO) mode, providing images as frequently as every 5-10 minutes. Complex storm-top structures were evident in the visible imagery, including numerous overshooting tops and anvil gravity waves. In addition, later in the animation a smoke plume can be seen approaching from the west (originating from a large fire that was burning in New Mexico). OKC denotes the location of Oklahoma City.

GOES-14 0.63 µm visible channel images (click image to play animation)

Not long after the first large thunderstorms began to develop west of Oklahoma City, a 1-km resolution POES AVHRR 12.0 µm IR channel image (below) displayed cloud-top IR brightness temperatures as cold as -78º C at 21:51 UTC or 4:51 PM local time (shortly before the first report of 1.25-inch diameter hail at 21:59 UTC). A 1-km resolution AVHRR vs 4-km resolution GOES-14 IR image comparison demonstrated two important advantages of polar-orbiter satellite imagery: (1) more accurate depiction of the coldest overshooting tops (-78º C on AVHRR, vs -64º C on with GOES-14), and (2) limited parallax error, helping to more accurately determine the true location of the overshooting tops.

POES AVHRR 12.0 µm IR channel image

AWIPS image combinations of GOES-14 10.7 µm IR channel data with overlays of Cloud Top Cooling (CTC) Rate and Overstooting Top (OT) Detection products (below; click image to play animation) showed the following: (1) the first region of significant CTC that was flagged with the newly-developing Oklahoma City storm was at 21:15 UTC, with a CTC rate of -8.8º C compared to the previous GOES-14 IR image; (2) the CTC rate increased to -26.9º C for the following 21:25 UTC IR image; (3) the CTC rate jumped to a remarkable -60.2º C for the following 21:32 UTC IR image (an indicator of the explosive rate of storm development); (4) OT detection icons began to appear once GOES-14 IR images exhibited IR brightness temperature values of -60º C and colder (beginning at 21:55 UTC).

GOES-14 10.7 µm IR image + Cloud Top Cooling Rate and Overshooting Top Detection products (click image to play animation)

===== 02 June Update =====

A comparison of before/after (14 May/02 June) 250-meter resolution true-color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (below) showed the damage path from the 31 May El Reno, Oklahoma tornado. The lakes and rivers appear brighter on the 02 June image due to sun glint off the bodies of water (the sun-satellite geometry was different than it was on 14 May).

Before/after (14 May/02 June) MODIS true-color Red/Green/Blue (RGB) images

The tornado damage path is also highlighted on the 02 June MODIS true-color RGB image, viewed using Google Earth (below).

MODIS true-color RGB image (viewed using Google Earth)

Posted in AVHRR, Cloud-Top Cooling, GOES sounder, GOES-14, Google Earth, MODIS, POES, Red/Green/Blue (RGB) images, Severe convection | No Comments »

Moore, Oklahoma tornado

May 20th, 2013

GOES-15 (left) and GOES-13 (right) 0.63 µm visible channel images (click image to play animation)

A devastating tornado struck Moore, Oklahoma just after 20:00 UTC or 3:00 PM local time on 20 May 2013, causing extensive (EF4 to EF5) damage and at least 24 fatalities. McIDAS images of GOES-15 (GOES-West) and GOES-13 (GOES-East) 0.63 µm visible channel data (above; click image to play animation; also available as a QuickTime movie) showed the line of rapidly-developing thunderstorms over southern and central Oklahoma during the early afternoon hours — Moore is located about halfway between Oklahoma City (OKC) and Norman (OUN). Earlier in the day the GOES-13 satellite had been placed into Rapid Scan Operations (RSO) mode (providing images as frequently as every 5-10 minutes), while the GOES-15 satellite was placed into Super Rapid Scan Operations (SRSO) mode (providing bursts of imagery at 1-minute intervals) after 20:15 UTC. According to the preliminary NWS damage survey, the tornado began around 19:45 UTC just west of Newcastle, and ended around 20:35 UTC just east of Moore.

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images

An AWIPS comparison of 1-km resolution Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images about an hour before the tornado arrived in Moore (above) revealed the presence of shadowing from overshooting tops and cloud-top IR brightness temperatures as cold as -68º C. About 30 minutes prior to the Moore tornado, a comparison of 1-km resolution Aqua MODIS 0.65 µm visible channel and 11.0 µm IR channel images (below) again indicated signatures of vigorous overshooting tops, with cloud-top IR temperatures as cold as -76º C.

Aqua MODIS 0.65 µm visible channel and 11.0 µm IR channel images

Comparisons of the 1-km resolution VIIRS 11.45 µm IR and MODIS 11.0 µm IR images with their corresponding 4-km resolution GOES-13 10.7 µm IR images (below) demonstrated the value of higher spatial resolution to aid in the earlier and more accurate detection of the cold cloud-top IR brightness temperatures values associated with these rapidly-developing convective cells. There were significant differences in the magnitude of the coldest cloud-top IR brightness temperatures with the more northerly cell that spawned the Moore tornado: -68 C on VIIRS vs -51 C on GOES, and -76 C on MODIS vs -62 C on GOES. The northwestward shift in the location of features on the GOES-13 images was due to parallax.

Comparison of 1-km resolution VIIRS 11.45 µm IR image and corresponding 4-km resolution GOES-13 10.7 µm IR image

Comparison of 1-km resolution MODIS 11.0 µm IR image and corresponding 4-km resolution GOES-13 10.7 µm IR image

A 250-meter resolution Aqua MODIS true-color Red/Green/Blue (RGB) image from the SSEC MODIS Today site (below; viewed using Google Earth) shows a closer view of the northernmost cell that produced the Moore tornado, along with hail as large as 3.25 inches in diameter (SPC storm reports).

MODIS true-color Red/Green/Blue (RGB) image

GOES-13 sounder Convective Available Potential Energy (CAPE) derived product images (below; click image to play animation) showed how the atmosphere rapidly destabilized during the day, with CAPE values in excess of 5000 J/kg (lighter purple color enhancement) at 18:00 UTC east of the stationary frontal boundary just prior to convective development.

GOES-13 sounder CAPE derived product images (click image to play animation)

Cloud Top Temperature retrievals created using data from the IASI, CrIS, and AIRS polar-orbiting sounder instruments (below; courtesy of Elizabeth Weisz and Nadia Smith, CIMSS) showed the rapid trend in cloud-top cooling during the 15:56-19:35 UTC timeframe.

Cloud Top Temperature retrievals from IASI, CrIS, and AIRS sounder instruments

Posted in GOES sounder, GOES-13, GOES-15, Google Earth, MODIS, Other Satellites, Red/Green/Blue (RGB) images, Severe convection, Suomi NPP, VIIRS | No Comments »

Smoke plume and “hot spot” from the Springs Fire in southern California

May 2nd, 2013

GOES-15 (left) and GOES-13 (right) 0.63 µm visible channel images (click image to play animation)

A comparison of McIDAS images of 1-km resolution GOES-15 (GOES-West) and GOES-13 (GOES-East) 0.63 µm visible channel data (above; click image to play animation) showed the smoke plume from the Springs Fire near Camarillo, California on 02 May 2013. GOES-15 (positioned over the Equator at 135º West longitude) had a better viewing angle of the smoke plume, while GOES-13 (positioned at 75º West longitude) was in Rapid Scan Operations (RSO) mode and was therefore able to provide more frequent images.

AWIPS images of 4-km resolution GOES-15 3.9 µm shortwave IR data (below; click image to play animation) showed the development and rapid growth of the fire “hot spot” signature (dark black enhancment) after 14:01 UTC (7:01 AM local time). At Point Mugu (station identifier KNTD), the surface winds gusted to 27 knots from the southwest at 17 UTC, then shifted and gusted to 30 knots from the northwest at 19 UTC, and then shifted again and gusted to 30 knots from the southwest at 20 UTC. Surface visibility at this site was reported to be as low as 2 miles to the north and northeast of the station, with an overcast layer of smoke during most of the day. Not far inland at Sandberg (station identifier KSDB), winds gusted to 46 knots and the dew point temperature dropped to -19º F (making for a relative humidity of 2%!).

GOES-15 3.9 µm shortwave IR images (click image to play animation)

===== 03 May Update =====

AWIPS images of 1-km resolution Suomi NPP VIIRS 3.74 µm shortwave IR and 0.7 µm Day/Night Band data at 09:41 UTC or 2:41 AM local time on 03 May (below) showed a very large fire “hot spot” (yellow to red to black color enhancement) on the shortwave IR image, and the Day/Night Band revealed the hazy signature of smoke aloft that had drifted offshore and south and southeastward along the southern California coast.

Suomi NPP VIIRS 3.74 µm shortwave IR and 0.7 µm Day/Night Band images

During the following afternoon on 03 May, 250-meter resolution true-color and false-color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (below) showed the dense smoke plume continuing to drift offshore; the hottest active fire regions appeared as light red features on the false-color image.