Mesoscale Convective System in South Dakota

August 27th, 2015

Suomi NPP VIIRS Infrared (11.45 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

Suomi NPP VIIRS Infrared (11.45 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

A large Mesoscale Convective System (MCS) developed over western South Dakota late in the day on 26 August 2015, moving eastward across the state and producing wind gusts as high as 79 mph (SPC storm reports). A nighttime comparison of Suomi NPP VIIRS Infrared (11.45 µm) and Day/Night Band (0.7 µm) images at 0842 UTC (above) showed the large cloud shield with cloud-top IR brightness temperatures as cold as -74º C at the central cluster of overshooting tops; bright white pixels on the Day/Night Band image were portions of the cloud illuminated by intense lightning activity. Various types of waves were also seen in the VIIRS imagery: (1) concentric gravity waves propagating outward from the central cluster of overshooting tops, (2) transverse banding emanating radially outward in portions of the northern semicircle of the MCS, and (3) a large arc of waves moving westward away from the back edge of the storm.

Regarding the large arc of waves along the back edge of the MCS, GOES-13 (GOES-East) water vapor (6.5 µm) images (below; click image to play animation) revealed a signal of strong subsidence (warming/drying, darker blue color enhancement) as the westward-expanding cloud mass was acting as an obstacle to the prevailing westerly winds coming from Wyoming and Montana.

GOES-13 water vapor (6.5 µm) images [click to play animation]

GOES-13 water vapor (6.5 µm) images [click to play animation]

Tornado in Lake Geneva, Wisconsin

August 19th, 2015
GOES-14 (left) and GOES-13 (right) 10.7 µm IR images.  Lake Geneva Wisconsin is indicated by the small white box [click to play animated GIF]

GOES-14 (left) and GOES-13 (right) 10.7 µm IR images. Lake Geneva Wisconsin is indicated by the small white box [click to play animated GIF]

An EF-1 Tornado struck Lake Geneva, WI after sunset on 18 August 2015 (SPC Storm Reports; NWS MKX report). GOES-14 was in SRSO-R mode, providing 1-minute imagery over the region; additionally, GOES-13 was in RSO mode, providing imagery about every 7 minutes. Unfortunately, GOES-14 requires two 15-minute breaks in scanning to perform housekeeping (Link); one of those periods is from 0130-0145 UTC, 13 minutes before the tornado touchdown at 0158 UTC. (GOES-R will not require these 15-minute breaks). The animation above pauses during that housekeeping time; it also slows for the ten minutes surrounding 0158 UTC. (Click here for an animation without the White Box signifying Lake Geneva).

The 0158 UTC imagery from GOES-14 (paired with the 0155 UTC imagery from GOES-13 is shown below. An overshooting top that is associated with the tornado is apparent (northeast of Lake Geneva because of the parallax shift). This overshoot is easily traceable in the 1-minute imagery, above, as it moves northeastward towards Lake Michigan. The feature also appears and can be tracked in GOES-13.

GOES-14 (left) and GOES-13 (right) 10.7 µm IR images, 0158 UTC 19 August 2015.  Lake Geneva Wisconsin is indicated by the small white box [click to enlarge]

GOES-14 (left) and GOES-13 (right) 10.7 µm IR images. Lake Geneva Wisconsin is indicated by the small white box [click to enlarge]

Automated detection of Overshooting Tops (and thermal couplets) (from this website) showed a cluster of Overshooting Tops moving over southeast Wisconsin at the time of the tornado. The number of Overshoots detected jumped about an hour before the tornado touchdown.

GOES-13 Automated Detection of Overshooting Tops (blue) and Thermal Couplets (Red) 2330 UTC 18 August 2015 - 0225 19 August 2015 [click to enlarge]

GOES-13 Automated Detection of Overshooting Tops (blue) and Thermal Couplets (Red) 2330 UTC 18 August 2015 – 0225 19 August 2015 [click to enlarge]

GOES-14 SRSO-R: Thunderstorms over the ArkLaMiss and Mid-Atlantic regions

August 11th, 2015

GOES-13 Infrared (10.7 µm) and Suomi NPP VIIRS Infrared (11.45 µm) images [click to enlarge]

GOES-13 Infrared (10.7 µm) and Suomi NPP VIIRS Infrared (11.45 µm) images [click to enlarge]

A nighttime mesoscale convective system (MCS) developed near the Arkansas/Louisiana/Mississippi border region after about 0700 UTC (2:00 AM local time) on 11 August 2015, and began to move southeastward. A comparison of 4-km resolution GOES-13 Infrared (10.7 µm) and 375-meter resolution Suomi NPP VIIRS Infrared (11.45 µm) images (above) showed the MCS around 0845 UTC, and highlighted the two advantages of polar-orbiter vs geostationary satellite imagery: (1) higher spatial resolution, for a more accurate assessment of the cloud-top IR Brightness Temperatures (the coldest GOES-13 IR BT was -73º C, while the coldest VIIRS IR BT was -83º C), and (2) minimal parallax error, for a more accurate geo-location of features such as thunderstorm overshooting tops (note how the storm appeared to be located farther to the northwest on the GOES image, centered over far southeastern Arkansas).

With the arrival of daylight the following morning, 1-minute interval GOES-14 SRSO-R visible (0.63 µm) images (below) revealed the presence of numerous short-lived overshooting tops which were penetrating the cirrus canopy of the persisting MCS. The formation of a well-defined outflow boundary was also seen, which continued to move southward during the late morning hours. The MP4 movie file is also available as a very large (73 Mbyte) animated GIF. A GOES-14 1-minute-image IR (10.7 µm) animation which shows the initial development and subsequent motion of the MCS can be seen here.

GOES-14 visible (0.63 µm) images [click to play MP4 animation]

GOES-14 visible (0.63 µm) images [click to play MP4 animation]

GOES-14 1-minute visible images (below) also showed the development of multi-cellular thunderstorms over parts of the Mid-Atlantic states, focused along trough axes ahead of an approaching cold frontal boundary — many of these thunderstorms produced damaging winds (SPC Storm Reports). The MP4 movie file is also available as a very large (102 Mbyte) animated GIF.

GOES-14 visible (0.63 µm) images [click to play MP4 animation]

GOES-14 visible (0.63 µm) images [click to play MP4 animation]

GOES-14 in SRSO-R Mode

August 10th, 2015

GOES-14 Visible (0.62 µm) Imagery  [click to play animation]

GOES-14 Visible (0.62 µm) Imagery [click to play animation]

GOES-14 is again in SRSO-R (Super Rapid Scan Operations for GOES-R) mode, affording the opportunity for 1-minute imagery over select regions of the United States. Information on the daily activity is available here; SRSO-R will continue through 21 August and serves as a reminder of the kind of routine scanning abilities that will be available when GOES-R is operational.

The images above, from the morning of 10 August, show a variety of features (thunderstorms over the Piedmont of South Carolina, North Carolina and Virginia, wave clouds over the high terrain of North Carolina, river valley fog in northern West Virginia and western Pennsylvania, fog in southern Vermont, etc.). High temporal resolution allows a better understanding of the cloud behavior.

As solar heating increased toward mid-day and the atmosphere became more unstable, clusters of convection developed over parts of the Great Lakes region as seen in the MP4 animation below. One of the thunderstorms (which developed in eastern Wisconsin ahead of an approaching cold front) produced 1.75-inch diameter hail, and a brief EF0 tornado (SPC storm reports); not far to the south, a thunderstorm wind gust of 44 mph and 1.10 inches of rainfall in 30 minutes occurred at Milwaukee International Airport (Local Storm Reports). The MP4 movie file is also available as a very large (197 Mbyte) animated GIF.

GOES-14 Visible (0.63 um) images [click to play animation]

GOES-14 Visible (0.63 um) images [click to play animation]

Over the Southeast US, widespread damaging wind reports resulted from strong thunderstorms forming ahead of a Mesoscale Convective Vortex that was moving southeastward across the Tennessee River Valley region (SPC Mesoscale Discussion). The GOES-14 visible images below vividly displayed the complex nature of the convection associated with this feature. The MP4 movie file is also available as a very large (87 Mbyte) animated GIF.

GOES-14 Visible (0.63 µm) images [click to play animation]

GOES-14 Visible (0.63 µm) images [click to play animation]

In the Northeast US, the GOES-14 visible images below showed convective development which was being aided by boundary layer convergence along a weak trough axis (surface analysis). 1.00-inch diameter hail was reported at Franklin in Upstate New York at 2035 UTC, and damaging winds were reported in Victor, New York at 2002 UTC and then again in Lyons, New York at 2129 UTC. The MP4 movie file is also available as a very large (59 Mbyte) animated GIF.

GOES-14 Visible (0.63 µm) images [click to play animation]

GOES-14 Visible (0.63 µm) images [click to play animation]

To access realtime GOES-14 1-minute data directly, click here or here.

One of the things SRSO-R supports is the 2015 Summer Experiment at the Aviation Weather Center. For more information on that experiment, click here.