GOES-15 « CIMSS Satellite Blog

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 »

Uncharacteristically cloud-free and warm across interior Alaska

June 17th, 2013

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

McIDAS images of GOES-15 0.63 µm visible channel data (above; click image to play animation) revealed an uncharacteristically cloud-free view of most of the interior of Alaska on 17 June 2013. A large blocking ridge of high pressure had been building across the region, which helped to set the stage for record high temperatures at a number of locations — on 16 June many sites reported daily maximum temperatures in the middle to upper 80s F, with a few sites hitting the 90º F mark (regional temperatures and precipitation). In south-central Alaska, several locations set all-time record highs on 17 June.

On the previous day, a comparison of AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel and 3.74 µm shortwave IR data (below) showed that the Alaska fire season was well underway, with a number of fire “hot spots” (black to yellow to red color enhancement) appearing on the shortwave IR image; some of these larger fires were producing smoke plumes that could be seen on the visible image. Again, note the unusually warm tempertures at many of the reporting sites. Smoke plumes from a couple of the larger fires could also be seen in southwestern and southeastern Alaska on the animation of GOES-15 visible images above. Closer views of pyrocumulonimbus clouds associated with the largest fires can be seen here.

Suomi NPP VIIRS 0.64 µm visible channel and 3.74 µm shortwave IR channel images

Posted in Arctic, AVHRR, Fire detection, GOES-15, POES, Suomi NPP, VIIRS | No Comments »

Unusually dry cut-off low near the southern California coast

June 9th, 2013

GOES-15 6.5 µm water vapor channel images (click image to play animation)

AWIPS images of GOES-15 6.5 µm water vapor channel data (above; click image to play animation) showed the formation of an unusually dry signature associated with a cut-off low near the coast of southern California during the 08 June – 09 June 2013 period. Water vapor channel brightness temperatures were as warm as -9.0º C (darker orange color enhancement), which is an abnormally warm/dry value to be seen on water vapor imagery.

This warm/dry signal was also very apparent on imagery from the 3 water vapor channels (6.5 µm, 7.0 µm, and 7.4 µm) that are available from the GOES-15 sounder (below; click image to play animation). These 3 GOES sounder water vapor channels sense the amount of mosture within 3 different vertical layers of the atmosphere, and are used to create the GOES sounder Total Precipitable Water (TPW) derived product — which in this case depicted TPW values as low as 11 mm or 0.43 inch at 18:00 UTC. The Blended Total Precipitable Water Percent of Normal product indicated that the TPW values within the dry cut-off low were generally 40-70% of normal for this time of year over that region.

GOES-15 Sounder and Imager water vapor channel images (click mage to play animation)

The very warm/dry signature seen on the GOES-15 water vapor imagery was well-correlated with elevated values of GOES-15 sounder Total Column Ozone, which suggests an abnormally low tropopause within that feature. This was verified with fields from the CRAS model, which indicated that the height of the dynamic tropopause (taken to be the PV1.5 surface) was as low as the 570 hPa pressure level at 18:00 UTC. GOES sounder Total Column Ozone values were as high as 382 Dobson Units within the dry cut-off low.

GOES-15 imager 6.5 µm water vapor channel image + GOES-15 sounder Total Column Ozone product (with overlays of CRAS model fields)

===== 10 June Update =====

Comparison of GOES-15 Sounder and Imager water vapor channel data

The dry cut-off low began to move inland over southern California on 10 June, and an AWIPS image comparison of GOES-15 Sounder and Imager water vapor channel data (above) showed that it was centered approximately over Vandenberg Air Force Base (KVBG) at around 12 UTC that morning. A comparison of the GOES-15 Sounder and Imager water vapor channel weighting functions (below) indicated that the individual water vapor channels were sensing radiation from layers that were at much lower altitudes in the dry air mass over Vandenberg, California than they were farther to the north over Medford, Oregon (KMFR) where the atmosphere had much more moisture distributed within the middle to upper troposphere.

Comparison og GOES-15 Sounder and Imager water vapor channel weighting function plots

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GOES-13 outage

May 22nd, 2013

Last GOES-13 10.7 µm image before outage

GOES-13 suffered an anomaly overnight: the satellite is no longer pointed towards the Earth for as yet unknown reasons. The anomaly started at 03:40 UTC on 22 May, and at 04:29 UTC, GOES-15 (GOES-West) began a 30-minute full disk scan schedule.

Last GOES-13 10.7 µm images before outage

Successive images from just before the anomaly (above), at nominal times of 03:15 UTC and 03:32 UTC, are shown. There is a large navigation offset (~200 km) apparent in the right panel, which panel shows the last scanned image from GOES-13 before the major anomaly. The offset is also apparent in the image at the top of the page (Look, for example, at Cuba, or in the northwest corner of the image)

GOES-14, in standby mode at 105.5 W longitude, has been activated; the first images from GOES-14 will be available at 05:00 UTC 23 May. There are no plans now to move GOES-14 from its current position. In the meantime, GOES engineers are working on a solution to GOES-13′s problems. An update from the Environmental Satellite Processing Center (ESPC) is scheduled for around Noon eastern time (see NOAA NESDIS GOES Special Bulletins). Note that GOES-14 data will *not* be relayed via GOES-13 — so ground station users will need to reposition their antennas to receive GOES-14 direct readout data.

In addition, GOES-12 (GOES-South America) continues to give coverage from its position over 60 W. Full-disk imagery is available every three hours, and routine sampling (both Imager and Sounder) continues and is available here.

– Note to NWS AWIPS Users –

GOES-15 (GOES-West) full-disk coverage

With the temporary loss of GOES-13 (GOES-East), the GOES-15 (GOES-West) satellite has been placed into Full Disk scan mode, which only provides imagery over CONUS every 30 minutes — and the quality of the imagery degrades over the eastern US (above), due to the very large view angle from GOES-15 (which is located at 135 West longitude). Parallax error is also greatly increased.

During such an outage of geostationary satellite data, imagery from polar-orbiting satellite instruments (such as Terra and Aqua MODIS, Suomi NPP VIIRS, and POES AVHRR) can be used when available to help fill in temporal data gaps, and also provide a much more detailed image in terms of spatial resolution (and with a lack of a large parallax error). The animation below covers the time period from 04:00 UTC to 11:00 UTC, showing the GOES-15 IR imagery at 30 minute intervals with the insertion of IR images from MODIS, VIIRS, and AVHRR when available. You can immediately see the value of the higher spatial resolution provided by the polar-orbiting satellite data.

Animation of GOES-15 IR images, with available polar-orbiter satellite IR images inserted

A direct comparison of GOES-15 and Suomi NPP VIIRS IR imagery around 07:00 UTC (below) again shows the better detail provided by the higher spatial resolution of VIIRS (along with a lack of parallax error) for severe thunderstorms that were producing large hail and damaging winds across parts of the lower Mississippi Valley region.

Comparison of 07:03 UTC Suomi NPP VIIRS IR image and 07:00 UTC GOES-15 IR image

In addition, the availability of a Day/Night Band on the VIIRS instrument can provide a “visible image at night”, which can be helpful for locating important features such as convective overshooting tops and low-level cloud edges (below).