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.

A mid-tropospheric atmospheric bore viewed by GOES-15, GOES-14, and GOES-13

May 16th, 2015

GOES-15 (left), GOES-14 (center), and GOES-13 (right) 6.5 µm water vapor channel images [click to play animation]

GOES-15 (left), GOES-14 (center), and GOES-13 (right) 6.5 µm water vapor channel images [click to play animation]

An elongated north-to-south oriented atmospheric bore was observed on GOES-15 (GOES-West), GOES-14, and GOES-13 (GOES-East) 6.5 µm water vapor channel images (above; click to play animation; also available as an MP4 movie file) on the morning of 16 May 2015. This bore feature was located in the area where strong westerly to southwesterly mid-tropospheric winds were impinging upon a consolidating dryline — this dryline later moved eastward and acted as the focus for severe thunderstorms across Texas (SPC storm reports). GOES-14 had been activated to perform Super Rapid Scan Operations for GOES-R (SRSOR) duties beginning on 18 May.

Note that there were no parallel cloud rolls present on the corresponding GOES-15/14/13 0.63 µm visible channel imagery (below) — so this gravity wave bore feature was forming in clear air.

GOES-15 (left), GOES-14 (center), and GOES-13 (right) 0.63 µm visible and 6.5 µm water vapor channel images

GOES-15 (left), GOES-14 (center), and GOES-13 (right) 0.63 µm visible and 6.5 µm water vapor channel images

A comparison of 12 UTC El Paso, Texas (yellow) and Midland, Texas (cyan) rawinsonde data (below) showed the differences in vertical moisture profile to the west and to the east of the bore feature — especially in the 500-600 hPa layer, where a good deal of the signal contributing to the overall water vapor brightness temperature was originating from.

El Paso and Midland, Texas rawinsonde data profiles

El Paso and Midland, Texas rawinsonde data profiles

GOES-15 Navigation Anomalies

May 4th, 2015
GOES-15 0.62 µm visible imagery, times as indicated on 3 May 2015 (click to enlarge)

GOES-15 0.62 µm visible imagery, times as indicated on 3 May 2015 (click to enlarge)

A GOES-15 (GOES-West) Star Tracker failed on 23 April 2015 at 2032 UTC. This leaves just one working Star Tracker; consequently image navigation has degraded. The image above shows three successive visible images centered near Crater Lake, OR, on 3 May 2015. The navigation shifts over time. An animation of 3.9 µm imagery, below, also from May 3rd (available here as an mp4), shows image navigation shifts throughout the day. A two-day animation of visible imagery centered on the Washington coast near Hoquiam (bottom, available here as an mp4) also shows the navigation anomalies that can be as much as 8 km in the infrared. Users who require precise animation in their GOES-15 imagery should be alert to this issue. NOAA/NESDIS, NASA and factory engineers are investigating possible fixes; GOES-15 status updates will appear here.

GOES-15 3.9 µm infrared imagery, 1400-2200 UTC on 3 May 2015 (Click to enlarge)

GOES-15 3.9 µm infrared imagery, 1400-2200 UTC on 3 May 2015 (click to enlarge)

GOES-15 0.62 µm infrared imagery, 1400-2200 UTC on 1 and 2 May 2015 (Click to enlarge)

GOES-15 0.62 µm infrared imagery, 1400-2200 UTC on 1 and 2 May 2015 (click to enlarge)

Thunderstorms in Arizona

May 4th, 2015
GOES-13 10.7 µm IR images (click to play animation)

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

4-km resolution GOES-13 (GOES-East) 10.7 µm IR channel images (above; click image to play animation) showed the development and northward propagation of clusters of thunderstorms across Arizona on 04 May 2015. The coldest cloud-top IR brightness temperature was -49º C (darker red color enhancement). As the storms later organized into a mesoscale convective system, cloud-to-ground lightning strikes were seen to exceed 100 per 15-minute period.

A higher resolution view could be seen in a comparison of Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB) and 11.45 µm IR channel images at 0940 UTC or 2:40 AM local time (below). Since the Moon was in the Waning Gibbous phase at 99% of full, this served as a good example of the “visible image at night” capability of the VIIRS Day/Night Band.

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR images, with METAR surface reports and 1-hour cloud-to-ground lightning strikes

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR images, with METAR surface reports and 1-hour cloud-to-ground lightning strikes

One ingredient that aided in the thunderstorm development was rich moisture, as was noted in this excerpt from a NWS Phoenix forecast discussion:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
840 AM MST MON MAY 4 2015

HOWEVER WHAT WAS NOT SO OBVIOUS…AND A MODEL FAILURE…WAS THE AMOUNT OF BOUNDARY LAYER MOISTURE ADVECTED INTO SOUTHERN AZ FROM MEXICO LATE YESTERDAY AFTERNOON AND NIGHT. JUST LOOK AT THIS MORNINGS TUCSON BALLOON SOUNDING. IT SHOWED AN 800 MB DEWPOINT OF 9 DEG C WHICH LOOKS MONSOONISH. IN OTHER WORDS THE BOUNDARY LAYER MOISTURE THROUGH 700 MB WAS IMPRESSIVE.

This northward transport of moisture could be seen on GOES-15 sounder Total Precipitatble Water (TPW) derived product images (below; click image to play animation); TPW values even exceeded 30 mm or 1.18 inches (yellow color enhancement) as early as 02 UTC on 04 May, reaching a peak of 33.4 mm or 1.3 inches at 04 UTC. A comparison of the Tucson rawinsonde data profiles from 12 UTC on 03 May and 00/12 UTC on 04 May can be seen here — TPW values at that location increased from 13.5 mm (0.53 inch) to 22.3 mm (0.88 inch) during that 24-hour period.

GOES-15 sounder Total Precipitable Water derived product images (click to play animation)

GOES-15 sounder Total Precipitable Water derived product images (click to play animation)

Later in the day on 04 May, as thunderstorms moved northward across the Interstate 40 corridor in northeastern Arizona, swaths of rain-cooled wet ground appeared as lighter-gray areas on the Aqua MODIS 11.0 µm IR image at 2008 UTC (below). These swaths of wet soil exhibited IR brightness temperatures that were as much as 10º C cooler than the adjacent dry soil surfaces which were heating up quickly during the early afternoon hours.

Terra (1828 UTC) and Aqua (2008 UTC) MODIS 11.0 µm IR images

Terra (1828 UTC) and Aqua (2008 UTC) MODIS 11.0 µm IR images

The corresponding 2008 UTC Aqua MODIS Land Surface Temperature (LST) product (below) made it easier to discriminate between the cooler swaths of wet ground (LST values between 70 and 85º F, shades of green) and the adjacent areas of dry soil (LST values as warm as 100-116º F, darker shades of orange).

Aqua MODIS Land Surface Temperature product

Aqua MODIS Land Surface Temperature product