Eruption of the Wolf Volcano in the Galapagos Islands

May 25th, 2015

GOES-13 0.63 µm visible channel (left) and 3.9 µm shortwave IR channel (right) images [click to play animation]

GOES-13 0.63 µm visible channel (left) and 3.9 µm shortwave IR channel (right) images [click to play animation]

After nearly 33 years of inactivity, a comparison of GOES-13 0.63 µm visible channel and 3.9 µm shortwave IR channel images (above; click to play animation; also available as an MP4 movie file) showed that the Wolf Volcano in the Galapagos Islands began to erupt sometime between 0645 and 0715 UTC on 25 May 2015. A large thermal anomaly or “hot spot” (red-enhanced pixels) was quite apparent, along with what appeared to be a brief post-eruption “shock wave” (warmer, darker gray enhancement) propagating radially outward from the eruption site on the 0715 and 0745 UTC shortwave IR images. Two plumes of volcanic cloud could be seen: a small one at a lower altitude propagating northeastward, and a second larger plume at a higher altitude moving south-southwestward.

With the arrival of daylight at 1215 UTC, a portion of the volcanic cloud could be seen at times (although identification was difficult with widespread meteorological clouds present in the area).

An Aqua MODIS false-color Red/Gren/Blue (RGB) image at 0800 UTC (below; courtesy of Michael Pavolonis, NOAA/NESDIS/CIMSS) displayed a signal of SO2 (green enhancement) along the edges of the larger volcanic cloud as it was moving southward.

Aqua MODIS false-color RGB image

Aqua MODIS false-color RGB image

GOES-13 10.7 µm IR channel images (below; click to play animation; also available as an MP4 movie file) indicated that the coldest cloud-top IR brightness temperature of -65º C appeared at 1015 UTC with the larger plume moving south-southwestward.

GOES-13 10.7 µm IR channel images [click to play animation]

GOES-13 10.7 µm IR channel images [click to play animation]

According to the nearby San Cristobal rawinsonde report at 12 UTC, the altitude of the -65º C temperature was around 14 km, at the 157 hPa pressure level. The tropopause for this sounding was coded to be at 16.1 km or 109.0 hPa, where the air temperature was -80.7º C.

San Cristobal, Galapagos Islands rawinsonde data profile

San Cristobal, Galapagos Islands rawinsonde data profile

The latest advisories issued by the Washington Volcanic Ash Advisory Center can be found here.

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.

Tropical Disturbance off the Southeast US Coast

May 7th, 2015
GOES-13 0.63 µm Visible images (click to play animation)

GOES-13 0.63 µm Visible images (click to play animation)

A disorganized subtropical system (Invest Area 90L) located over the southwest Atlantic to the east of Georgia and north of the Bahamas has the potential to become the first named system of the 2015 Atlantic Tropical Season (if named as a subtropical storm, this would be Ana). Visible imagery, above, shows a low-level swirl that is separated from any convection. However, during the 6 hours of the animation, the low-level swirl moves westward, moving more closely to active convection over the Gulf Stream. [Update, 2100 UTC 7 May: later images in the visible animation, above, showed strong convection developing over the surface circulation; another visible image animation with ship reports can be seen here]

Sea-surface temperatures (link) and wind shear (link) from the CIMSS Tropical Cyclones site show nominal conditions for strengthening.

MetOp-A passed over the southeast United States just after 1500 UTC on 7 May. The ASCAT scatterometer data (below) show a well-defined low-level circulation (with most winds just below tropical storm force) south and east of the deepest convection off the South Carolina/Georgia coasts.

ASCAT_07May2015

ASCAT winds from Metop-A and GOES-13 10.7 µm imagery, both near 1500 UTC on 7 May 2015; Surface observations from Fixed Buoys are also plotted (click to enlarge)

Suomi NPP overflew this system at 0700 UTC on 7 May, and imagery from the VIIRS Day/Night Band gave information that allowed a definitive estimate of the location of a low-level circulation. A comparison of the 0702 imagery, below, and the 1826 UTC imagery, following, shows changes in the organization and vertical structure of the developing system.

ASCAT_07May2015

Suomi NPP 11.45 µm infrared and 0.70 µm DayNight band visible imagery at 0702 UTC on 7 May 2015 (click to enlarge)

ASCAT_07May2015

As above, but at 1826 UTC on 7 May 2015 (click to enlarge)

Suomi NPP 1.61 µm near-infrared imagery can be used during the day to identify cirrus clouds: ice particles absorb (and do not reflect) radiation in these near-infrared wavelengths, but water droplets reflect. Thus, ice clouds appear dark. In the visible, both water and ice clouds are bright. The toggle below shows the 1.61 and the Visible imagery from Suomi-NPP.

ASCAT_07May2015

Suomi NPP 1.61 µm near-infrared and 0.65 µm visible imagery at 1826 UTC on 7 May 2015 (click to enlarge)

At 2006 UTC, the International Space Station’s RapidScat instrument provided surface scatterometer winds (below) that depicted the broad circulation of Invest AL90; the strongest winds were located farther away from the center of the feature.

GOES-13 0.63 µm visible image with an overlay of RapidScat surface scatterometer winds

GOES-13 0.63 µm visible image with an overlay of RapidScat surface scatterometer winds

08 May Update: Invest Area AL90 was upgraded to Subtropical Storm Ana by the National Hurricane Center around 02 UTC. A Terra MODIS 11.0 µm IR image at 0249 UTC is shown below, with overlays of the MSLP analysis, buoy reports, and RTMA surface winds.

Terra MODIS 11.0 µm IR channel image, with MSLP analysis, buoy reports, and RTMA surface wind analysis

Terra MODIS 11.0 µm IR channel image, with MSLP analysis, buoy reports, and RTMA surface wind analysis

A few hours later, a 0643 UTC comparison of Suomi NPP VIIRS 11.45 µm IR and 0.7 µm “visible image at night” Day/Night Band data is shown below.

Suomi NPP VIIRS 11.45 µm IR and 0.7 µm Day/Night Band images

Suomi NPP VIIRS 11.45 µm IR and 0.7 µm Day/Night Band images

For more information on this system, see the National Hurricane Center website.

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