Severe thunderstorm over West Texas, as viewed from 3 GOES satellites

May 19th, 2015

GOES-15 (left), GOES-14 (center), and GOES-13 (right) 0.62 µm visible channel images [click to play animation]

GOES-15 (left), GOES-14 (center), and GOES-13 (right) 0.62 µm visible channel images [click to play animation]

Thunderstorms began to develop across West Texas during the afternoon hours on 19 May 2015, along and ahead of an eastward-moving dryline. One of the storms went on to produce a few brief tornadoes, and hail as large as 3.0 inches in diameter (SPC storm reports). Different views of this storm were provided by GOES-15 (GOES-West), GOES-14 (in SRSO-R mode), and GOES-13 (GOES-East) 0.62 µm visible channel images (above; click image to play 190 MB animated GIF; also available as an MP4 movie file, or on YouTube). This comparison highlights the advantages of 1-minute interval Super Rapid Scan images (which will be available from GOES-R) compared to the standard 15-minute interval Routine Scan images provided by the current generation of GOES.

One interesting feature seen on the visible channel images above was the apparent merger of the large dominant dryline storm and a smaller northward-moving storm that had formed in Mexico (radar animation). In GOES-13 10.7 µm IR imagery with an overlay of SPC storm reports (below; click image to play animation), one report of 2.0-inch diameter hail was seen around or shortly after the time of the storm merger.

GOES-13 10.7 µm IR channel images (click to play animation)

GOES-13 10.7 µm IR channel images (click to play animation)

With higher spatial resolution IR imagery from MODIS (1-km), VIIRS (375-meter), and AVHRR (1-km), much colder cloud-top IR brightness temperatures were seen (below) compared to the corresponding 4-km resolution GOES IR imagery at those times — especially during the early formative stages of the thunderstorms captured with MODIS and VIIRS. The coldest cloud-top IR brightness temperature on the 2128 UTC AVHHRR image was -80º C, compared to -67º C on the 2130 UTC GOES image.

Terra and Aqua MODIS 11.0 µm, Suomi NPP VIIRS 11.45 µm, and POES AVHRR 12.0 µm IR channel images

Terra and Aqua MODIS 11.0 µm, Suomi NPP VIIRS 11.45 µm, and POES AVHRR 12.0 µm IR channel images

A more detailed discussion of this event can be found on the RAMMB GOES-R Proving Ground Blog.

GOES-14 in SRSO-R Scanning

May 18th, 2015

GOES-14 0.62 µm visible imagery [click to play animation]

GOES-14 0.62 µm visible imagery [click to play animation]

GOES-14 is producing imagery at 1-minute intervals as part of Super-Rapid Scan Operations for GOES-R (SRSO-R). Sectors that are scanned change each day and are determined by likely weather events. The animation above, in the southwest corner of the Monday May 18 sector shows strong convection over northern Louisiana. (A similar animation in mp4 format is available here (YouTube)) A benefit of 1-minute imagery is that it can capture the entire lifecycle of overshooting tops, cloud-top features that typically form and decay in less than 10 minutes.

GOES-R is scheduled to launch in March 2016. It will have the capability to provide routine 1-minute imagery over mesoscale-sized domains such as those sampled in the next three weeks by GOES-14. Real-time GOES-14 SRSO imagery is available through the SSEC RealEarth web map server and the GOES-14 SRSOR Imagery site.

Rapid Scan Operations allow the eye to distinguish between upper- and lower-level clouds that typically move at different speeds or in different directions. In the animation below (similar mp4 available here), high clouds over western Pennsylvania are moving over dissipating river fog in the central part of the state. Upper level clouds over southern New York are moving southward; low clouds are moving westward behind a back-door cold front: winds at White Plains, Newark, Trenton (and other stations) have all switched to easterly.

GOES-14 0.62 µm visible imagery [click to play animation]

GOES-14 0.62 µm visible imagery [click to play animation]

Another feature of interest was a thin layer of lake fog that was streaming northward across Lake Michigan during the morning hours, as seen in the animation below (also available as an mp4 movie file). Note the appearance of an undular bore propagating southeastward through the northern portion of the fog at the end of the animation; this may have been caused by an internal reflection of the strong southerly flow impinging upon the rugged southern coastline of the Upper Peninsula of Michigan. According to buoy data and the Terra MODIS Sea Surface Temperature product, Lake Michigan waters were still in the upper 30s to low 40s F — it was the pre-cold-frontal southerly flow of much warmer air with dew point values in the 50s and 60s F that led to the formation of the lake fog.

GOES-14 0.62 um visible channel images (click to play animation)

GOES-14 0.62 um visible channel images [click to play animation]

Rounds of deep convection persisted over parts of the Gulf Coast states during the day, which can be seen in the sunrise-to-sunset animation of GOES-14 visible images below (also available as an MP4 movie file). In Louisiana, some of these storms produced heavy rainfall and flash flooding, with a few water rescues necessary.

GOES-14 0.62 µm visible channel images (click to play YouTube animation)

GOES-14 0.62 µm visible channel images (click to play YouTube animation)

Dust storm in southern Nevada and California

April 14th, 2015
GOES-13 0.63 µm visible channel images (click o play animation)

GOES-13 0.63 µm visible channel images (click o play animation)

GOES-13 (GOES-East) 0.63 µm visible channel images (click image to play animation; also available as an MP4 movie file) showed the hazy signature of a cloud of thick blowing dust moving southward across southern Nevada and parts of southern California, along and behind a strong cold frontal boundary on 14 April 2015.

Areas where the dust cloud was more dense could be identified using the Terra and Aqua MODIS 11-12 µm IR brightness temperature difference (BTD) product (below). The 12 µm IR channel is no longer available on the imager instrument of the current series of GOES satellites — however, the ABI instrument on the upcoming GOES-R satellite will have a 12 µm IR channel, allowing the creation of such BTD products to aid in the identification and tracking of similar dust features.

Terra and Aqua MODIS 11-12 µm IR brightness temperature difference

Terra and Aqua MODIS 11-12 µm IR brightness temperature difference

At 1833 UTC, a pilot reported that the top of the dust cloud was at 11,500 feet near its leading edge (below). Farther to the south, strong winds interacting with the terrain were causing pockets of moderate to severe turbulence.

Terra MODIS 11-12 µm IR brightness temperature difference, with pilot reports

Terra MODIS 11-12 µm IR brightness temperature difference, with pilot reports

The blowing dust cloud was also evident on true-color Red/Green/Blue (RGB) images from MODIS and VIIRS, as visualized using the SSEC RealEarth web map server (below).

MODIS and VIIRS true-color RGB images

MODIS and VIIRS true-color RGB images

Extratropical Cyclogenesis over the western Pacific

March 30th, 2015
Himawari-8 AHI 0.64 µm visible channel images (click to play animation)

Himawari-8 AHI 0.64 µm visible channel images (click to play animation)

The AHI Instrument on Himawari-8 has 16 different channels sensing the atmosphere. The instrument is still in Post-Launch Testing, a period when instrument performance is monitored and adjusted. Extratropical cyclogenesis that occurred east of Japan on 30 March was captured by the different channels.

The 0.64 µm visible imagery, above, is the highest-resolution channel on AHI, with nominal 0.5-km resolution at the subsatellite point. The imagery above — at 1.5 km resolution and every 10 minutes — shows the development of an extratropical cyclone east of the main island of Japan (visible at the left edge of the imagery). Thin cirrus is spreading north of the storm and convection is developing both in the cool air north of the surface circulation center and along the cold front that is just to the west of the cirrus shield associated with the warm conveyor belt. Northerly surface winds north of the system and southern surface winds south of the system speak to the strengthening of the frontal boundary along which the storm is developing.

Himawari-8 AHI 0.85 µm infrared channel images (click to play animation)

Himawari-8 AHI 0.85 µm infrared channel images (click to play animation)

The 0.85 µm imagery, above, is in the near-infrared part of the electromagnetic spectrum, at wavelengths just a bit longer than red visible light (which is at 0.7 µm). It does an excellent job highlighting the land/water contrast (because bodies of water strongly absorb 0.85 µm solar radiation and land and clouds reflects it). This channel also is sensitive to vegetation. The larger-scale view shows jetstream cirrus south and southwest of the developing storm and an occluded system decaying to the east of Kamchatka.

The 0.46 µm imagery, below, is in the visible part of the electromagnetic spectrum, and is quite sensitive to aerosols (Click here for a fact sheet on ABI’s 0.46 µm “Blue Band”; fact sheets for all ABI Bands will be here in the future). The smog and pollution that surrounds Tokyo is more apparent in this imagery. Smog is also indicated near Osaka and Nagoya. A toggle between 0.64 µm, 0.46 µm and 0.85 µm imagery, here, from 30 March 2015 at 0000 UTC allows a comparison of the imagery.

Himawari-8 AHI 0.46 µm visible channel images (click to play animation)

Himawari-8 AHI 0.46 µm visible channel images (click to play animation)

The 1.60 µm imagery on AHI is useful because it can distinguish between clouds with water droplets (that scatter and reflect solar 1.60 µm radiation very effectively) and clouds with ice crystals (that absorb 1.60 µm radiation). In a standard enhancement, clouds with ice crystals appear grey, clouds with water droplets appear white. In the animation below, the glaciated cirrus canopy of the warm conveyor belt is readily apparent. Note also how the convection developing along the warm front has glaciated by the end of the animation.

Himawari-8 AHI 1.60 µm infrared channel images (click to play animation)

Himawari-8 AHI 1.60 µm infrared channel images (click to play animation)

The 3.9 µm on Himawari-8 provide detailed information about the sea surface temperature if clouds are not present, as was the case over the Kuroshio Current just east of Japan on 30 October. The animation below shows little change over 2 hours, as expected, except along the north wall of the current. Brightness Temperatures drop 10 C across the temperature gradient at the north end of the current.

Himawari-8 AHI 3.90 µm infrared channel images (click to play animation)

Himawari-8 AHI 3.90 µm infrared channel images (click to play animation)