Fatal severe weather outbreak in Oklahoma

March 25th, 2015
GOES-13 0.63 µm visible channel images (click to play animation)

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

Severe thunderstorms developed in the vicinity of a quasi-stationary frontal boundary which stretched from northeastern Oklahoma into northern Arkansas and southern Missouri late in the day on 25 March 2015. A plot of the SPC storm reports shows that these storms produced widespread large hail, damaging winds, and tornadoes —  including the first tornado-related fatality of 2015 at a trailer home park near Sand Springs, Oklahoma (just west/southwest of Tulsa). Storm reports also included hail as large as 4.25 inches in diameter, and wind gusts as high as 80 mph. 1-km resolution GOES-13 (GOES-East) 0.63 µm visible channel images (above; click image to play animation) showed the development of numerous thunderstorms across the region, some of which grew to be very large discrete supercells late in the afternoon and toward sunset. The tell-tale signature of cloud-top shadows from small-scale “overshooting tops” could be seen with many of these storms, indicating the presence of vigorous updrafts which penetrated the thunderstorm top (and likely the tropopause). Also note the presence of parallel bands of stable wave clouds over parts of northeastern Kansas and northwestern Arkansas: these clouds highlighted areas where boundary layer warm air advection was over-running shallow pockets of cool, stable air north frontal boundary.

The corresponding 4-km resolution GOES-13 10.7 µm IR channel images (below; click image to play animation) revealed very cold cloud-top IR brightness temperatures (as cold as -71º C, dark black color enhancement), along with the formation of a well-defined Enhanced-V/Thermal Couplet (EV/TC) signature with the storm that produced large hail, damaging winds, and the fatal tornado southwest of Tulsa (station identifier KTUL). The EV/TC signature was first evident on the 22:00 UTC IR image, with cold/warm thermal couplet values of -65º/-53º C; the maximum thermal couplet spread was at 22:25 UTC, with -71º/-52º C, after which time the minimum IR brightness temperatures of the overshooting tops then began a warming trend: -67º C at 22:30 UTC, and -64º C at 22:37 UTC (suggesting a collapse of the vigorous updraft and overshooting top). Note that the storm-top EV/TC signature was displaced to the northwest of the surface hail/wind/tornado storm reports just west of Tulsa, due to parallax resulting from the large satellite viewing angle of GOES-East (which is positioned over the Equator at 75º W longitude). In addition, see the bottom of this blog post for examples of the NOAA/CIMSS ProbSevere product applied to these storms.

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

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

Automated overshooting top (OT) detection icons (small yellow thunderstorm symbols) are also plotted on the GOES-13 IR images. The initial OT detections began at 20:15 UTC, over the general area where there was later a report of 1.0-inch diameter hail at 20:40 UTC. A comparison of the 4-km resolution GOES-13 10.7 µm IR image at 20:15 UTC with a 375-meter (projected onto a 1-km AWIPS grid) Suomi NPP VIIRS 11.45 µm IR image at 20:16 UTC (below) demonstrates (1) the advantage of improved spatial resolution for detecting the minimum cloud-top IR brightness temperature of thunderstorm overshooting tops (-60º C with GOES, vs -75º C with VIIRS), and (2) minimal parallax effect with polar-orbiting satellite imagery such as that from Suomi NPP, for more accurate geolocation of such potentially important storm features.

GOES-13 10.7 µm IR and Suomi NPP VIIRS 11.45 µm IR channel images

GOES-13 10.7 µm IR and Suomi NPP VIIRS 11.45 µm IR channel images

A comparison of 1-km resolution POES AVHRR 0.86 µm visible channel and 12.0 µm IR channel images (below) provided a detailed view of the storms at 22:54 UTC, which were electrically very active at that time (producing over 1900 cloud-to-ground lightning strikes in a 15-minute period). The coldest cloud-top IR brightness temperature was -77º C, located just southwest of Tulsa — this was likely the overshooting top associated with the supercell thunderstorm that produced the fatal tornado.

POES AVHRR 12.0 µm IR channel and 0.86 µm visible channel images, with METAR surface reports, lightning, and SPC storm reports

POES AVHRR 12.0 µm IR channel and 0.86 µm visible channel images, with METAR surface reports, lightning, and SPC storm reports

10-km resolution GOES-13 sounder Convective Available Potential Energy (CAPE) derived product images (below; click image to play animation) showed the rapid trend in destabilization of the air mass along and south of the frontal boundary, with CAPE values eventually exceeding 4300 J/kg (purple color enhancement).

GOES-13 sounder Convective Available Potential Energy (CAPE) derived product images (click to play animaton)

GOES-13 sounder Convective Available Potential Energy (CAPE) derived product images (click to play animaton)

10-km resolution GOES-13 sounder Total Precipitable Water (TPW) derived product images (below; click image to play animation) indicated that TPW values of 30 mm or 1.18 inch and greater (yellow enhancement) were present along and south the frontal boundary in northeastern Oklahoma.

GOES-13 sounder Total Precipitable Water derived product imagery (click to play animation)

GOES-13 sounder Total Precipitable Water derived product imagery (click to play animation)

At 19:19 UTC, the 4-km resolution MODIS Total Precipitable Water derived product image (below) showed a plume of moisture with TPW values as high as 41.7 mm or 1.64 inches (red enhancement) moving toward the Tulsa area.

MODIS 0.65 um visible channel and Total Precipitable Water derived product images

MODIS 0.65 um visible channel and Total Precipitable Water derived product images

Additional information about this event can be found at the NWS Tulsa and United States Tornadoes sites.

Test of GOES-15 (GOES-West) Rapid Scan Operations (RSO) sectors for the Alaska Region

March 17th, 2015
GOES-15

GOES-15 “Sitka” RSO Sector

During a 4-hour period on 17 March 2015, NOAA/NESDIS conducted a test of two special GOES-15 (GOES-West) Rapid Scan Operations (RSO) sectors for the Alaska Region. From 16:00 to 18:00 UTC, the test was conducted for the “Sitka” sector (above) — and GOES-15 0.63 µm visible channel images over a portion of that sector (below; click image to play animation) showed the circulation of a mid-latitude cyclone that was producing gale force winds in the eastern portion of the Gulf of Alaska (IR image with surface analysis), as well as clusters of deep convection which were forming along an occluded front approaching from the south.

GOES-15 0.63 µm visible images -

GOES-15 0.63 µm visible images – “Sitka” sector (click to play animation)

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GOES-15

GOES-15 “TPARC” RSO sector

Then from 18:00 to 20:00 UTC, the RSO test was conducted for the “TPARC” sector (above) — and GOES-15 0.63 µm visible channel images (below; click image to play animation) showed the circulation of two cyclones south of the Aleutian Islands, in addition to a large “banner cloud” and a few mountain waves which had formed downwind (to the north) of the rugged terrain of the Alaska Peninsula and the Aleutian Islands. GOES-15 IR brightness temperatures associated with the banner cloud were as cold as -65 C, which according to the nearby Bethel, Alaska rawinsonde data at 12 UTC corresponded to an altitude of around 27,700 feet (IR image with Bethel Skew-T and surface analysis).

GOES-15 0.63 µm visible channel images -

GOES-15 0.63 µm visible channel images – “TPARC” sector (click to play animation)

Regarding the Alaska Peninsula banner cloud seen on the GOES-15 visible images, a sequence of Terra/Aqua MODIS 11.0 µm and Suomi NPP VIIRS 11.45 µm IR images (below; click image to play animation) showed the evolution of this feature several hours before and after the RSO test. There were a few pilot reports of moderate turbulence, at altitudes as high as 36,000 feet – and some of these pilot reports specifically mentioned “MNT WAVE” in their remarks.

Suomi NPP VIIRS 11.45 µm IR image (click to play animation of VIIRS and MODIS IR images)

Suomi NPP VIIRS 11.45 µm IR image (click to play animation of VIIRS and MODIS IR images)

The CLAVR-x POES AVHRR Cloud Top Height product (below; click image to play animation) indicated that the banner cloud reached heights of 9 km (darker green color enhancement).

POES AVHRR Cloud Top Height product (click to play animation)

POES AVHRR Cloud Top Height product (click to play animation)

Eruption of the Villarrica volcano in central Chile

March 3rd, 2015
Suomi NPP VIIRS 0.7 µm Day/Night Band, 1.6 µm near-IR, 3.9 µm shortwave IR, and 11.45 µm longwave IR images

Suomi NPP VIIRS 0.7 µm Day/Night Band, 1.6 µm near-IR, 3.9 µm shortwave IR, and 11.45 µm longwave IR images

There was an explosive eruption of the Villarrica volcano in central Chile on the morning of 03 March 2015; the Buenos Aires VAAC issued their first volcanic ash advisory based upon initial detection on 06:38 UTC GOES-13 imagery, although media report and blog sources indicated that the eruption started closer to 06:00 UTC (3 am local time). A comparison of 06:07 UTC Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB), 1.6 µm near-IR, 3.9 µm shortwave IR, and 11.45 µm longwave IR images (above; courtesy of William Straka, SSEC) revealed a bright glow on the DNB and near IR images, with a pronounced “hot spot” evident on the shortwave IR (yellow to orange pixels; the hottest shortwave IR brightness temperature was over 600 K!) and even the longwave IR (darker black pixels) images. The DNB image was particularly striking, with nearby clouds and surface features being illuminated by the eruption.

MODIS and GOES-13 multispectral false-color Red/Green/Blue (RGB) images from the NOAA/CIMSS Volcanic Cloud Monitoring site (below; click image to play animation) showed that there was detection of a thermal anomaly or “hot spot” (indicated by a red box) as early as 04:20 UTC (MODIS) and 05:45 UTC (GOES-13); the volcanic cloud filament — which was estimated to be at an altitude of 30,000 feet — could be seen drifting to the southeast following the eruption.

MODIS and GOES-13 false-color RGB images (click to play animation)

MODIS and GOES-13 false-color RGB images (click to play animation)

On GOES-13 10.7 µm IR channel images (below; click image to play animation), the volcanic cloud initially exhibited an IR brightness temperature as cold as -42ºC  (green color enhancement), but the cloud filament quickly became very diffuse and difficult to identify on the IR images by 09:38 UTC.

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

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

The 12 UTC rawinsonde profiles from Puerto Montt, Chile (station identifier SCTE) on 02 March and 03 March are shown below. On the 02 March profile, the -42º C temperature was at an altitude around 9400 meters or 30,800 feet; on the 03 March profile, -42º C was around 9100 meters or 29,900 feet.

Puerto Montt, Chile 12 UTC rawinsonde profiles on 02 March and 03 March

Puerto Montt, Chile 12 UTC rawinsonde profiles on 02 March and 03 March

On GOES-13 3.9 µm shortwave IR images (below; click image to play animation) a “hot spot” (black to yellow to red color enhancement) was seen for several hours after the initial eruption. The highest shortwave IR brightness temperature observed by GOES-13 was 340.8 K — much lower than than the >600 K observed with the higher spatial resolution Suomi NPP VIIRS instrument.

GOES-13 3.9 µm shortwave IR channel images (click to play animation)

GOES-13 3.9 µm shortwave IR channel images (click to play animation)

Mesovortex over Lake Ontario

February 17th, 2015
GOES-13 0.63 µm visible channel images (click to play animation)

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

GOES-13 (GOES-East) 0.63 µm visible channel images (above; click to play animation) revealed the presence of a mesocale vortex (“mesovortex”) propagating eastward across the ice-free waters of western Lake Ontario on on 17 February 2015. At the beginning of the animation, also note that there were numerous “hole punch clouds” seen in the stratus cloud deck that covered the western Lake Ontario region during the early morning hours; these holes were likely caused by aircraft inbound/outbound from the Toronto International Airport — particles in jet engine exhaust act as ice nuclei, causing supercooled water droplets to turn into larger, heavier ice particles which then fall out of the cloud to create holes (sometimes described as “fall streaks” due to their appearance).

A closer view using a sequence of MODIS and VIIRS true-color Red/Green/Blue (RGB) images from the SSEC RealEarth web map server site is shown below. There was a significant amount of ice in the northeastern section of Lake Ontario, as well as a ring of offshore ice around other parts of the lake.

MODIS and VIIRS true-color images

MODIS and VIIRS true-color images

A comparison of the 16:31 UTC Terra MODIS 0.65 µm visible channel and the corresponding Sea Surface Temperature product (below) showed that SST values in the ice-free portions of the mesovortex path were generally in the 30 to 34º F  range.

Terra MODIS 0.65 µm visible channel image and Sea Surface Temperature product

Terra MODIS 0.65 µm visible channel image and Sea Surface Temperature product