Severe thunderstorms over the Gulf of Mexico

March 6th, 2014
Suomi NPP VIIRS 11.45 µm IR channel and 0.7 µm Day/Night Band images (with CG lightning strikes)

Suomi NPP VIIRS 11.45 µm IR channel and 0.7 µm Day/Night Band images (with CG lightning strikes)

A night-time AWIPS image comparison of Suomi NPP VIIRS 11.45 µm IR and 0.7 µm Day/Night Band data (above) showed a large mesoscale convective system (MCS) over the Gulf of Mexico at 07:08 UTC (2:08 AM local time) on 06 March 2014. On the IR image, brightness temperatures were as cold as -80º C on the far southern end of the storm, which had developed in the warm sector of a developing area of low pressure (surface frontal analysis). The Day/Night Band image revealed: (1) numerous bright west-to-east oriented “lightning streaks” caused by intense lightning activity illuminating the MCS cloud and cloud top — note that there were over 1300 cloud-to-ground (CG) lightning strikes detected in a 15-minute period, and (2) arc-shaped mesospheric airglow waves propagating northward and northeastward away from the region of vigorous overshooting tops at the southern end of the MCS.

A comparison of the 375-meter resolution Suomi NPP VIIRS 11.45 µm IR image with a 4-km resolution GOES-13 10.7 µm IR image (below) showed that the higher spatial resolution of the VIIRS data provided much clearer view of the various cloud structures along with a better depiction of the values of the cloud-top IR brightness temperatures.

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

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

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

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

GOES-13 10.7 µm IR channel images (above; click image to play animation) showed the evolution of the MCS as it continued to move eastward toward Florida. A squall line developed along the leading edge of the MCS, which played a role in producing a few tornadoes and areas of damaging winds over the southern half of the Florida peninsula (below).

Plot of SPC storm reports

Plot of SPC storm reports

Strong Storm in the Mediterranean

November 19th, 2013
Meteosat-10 10.8 µm infrared channel images (click to play animation)

Meteosat-10 10.8 µm infrared channel images (click to play animation)

Cyclone Cleopatra moved through the central Mediterranean Sea, causing flooding in Italy and Sardinia (BBC News Link) with northeastern Sardinia particularly hard hit. The infrared imagery from Meteosat-10, above, and the water vapor imagery, below, shows the slow movement of the entire system within the Mediterranean basin, as well as the strong thunderstorms over Sardinia later in the day on 18 November. Note in the Infrared animation that the minor eruption of Etna, on Sicily, is apparent (as documented here).

Meteosat-10 6.2 µm water vapor channel images (click to play animation)

Meteosat-10 6.2 µm water vapor channel images (click to play animation)

A higher-resolution view centered on Sardinia, below, shows the redevelopment of strong thunderstorms (inferred by cold cloud tops on the IR imagery) over Sardinia ending after 1800 UTC on 18 November as dry air swept north. The visible imagery (bottom) is also testimony to the training aspect of this convection. (Hat tip to Byron Grisham at NOAA/OSPO for alerting us about this noteworthy storm)

Meteosat-10 10.8 µm infrared channel images (click to play animation)

Meteosat-10 10.8 µm infrared channel images (click to play animation)

Meteosat-10 0.7 µm visible channel images (click to play animation)

Meteosat-10 0.7 µm visible channel images (click to play animation)

Satellite Views of an Historic Severe Weather Outbreak

November 17th, 2013
MODIS Visible (0.68 µm) and Infrared (11 µm) imagery from 1634 UTC 17 November overlain with hourly severe reports from 1700 and 1800 UTC (click to enlarge)

MODIS Visible (0.68 µm) and Infrared (11 µm) imagery from 1634 UTC 17 November overlain with hourly severe reports from 1700 and 1800 UTC (click to enlarge)

A late-season tornadic outbreak occurred on Sunday November 17th over the Upper Midwest. The animation above shows MODIS Imagery — visible and 11 µm just as the severe weather was erupting over Illinois. Two different sets of severe weather reports are overlain: those within an hour of the image, and those an hour after the image. The convection over central Illinois has just started to produce severe weather, and it intensified after the imagery (as seen by the blossoming in areal coverage of severe weather reports).

GOES-13 Enhanced Infrared (10.8 µm) imagery 17 November, times as indicated (click image to animate)

GOES-13 Enhanced Infrared (10.8 µm) imagery 17 November, times as indicated (click image to animate)

An animation of GOES-13 10.7 µm imagery (in RSO mode during the day), above, (also available here, on YouTube) shows the storms. The storm tops were not particularly cold (unsurprising given the date), but severe weather signatures (enhanced Vs, for example), can be discerned. Storm reports from SPC suggest that the strongest tornado, in Washington (in Tazewell County), was on the ground at 1700 UTC. The 1655, 1702 and 1710 UTC images shows a strong cell, but not one with particularly cold tops. An animation of these 3 images is shown below. The storm is relatively small compared to GOES-13 resolution. Note also that the storm appears to be north of Tazewell County because of parallax errors.

GOES-13 Enhanced Infrared (10.8 µm) imagery 17 November, times as indicated (click image to animate) Washington is in far northern Tazewell County, which County is outlined in White

GOES-13 Enhanced Infrared (10.8 µm) imagery 17 November, times as indicated (click image to animate) Washington is in far northern Tazewell County, which County is outlined in White

The large-scale environment was unusually moist and unstable for November. Total Precipitable Water exceeded 200% of normal over much of the upper midwest (link), and an animation of GOES-13 Sounder imagery of DPI Lifted Index (link) showed instability, albeit in between holes in the cloud (the extensive cloud shields suggest that solar heating played little role in this outbreak). The 1700 UTC GOES DPI Lifted Index image is below. Lifted Indices below -5 are common throughout Illinois. (GOES-13 Sounder data continues to have missing data points, as noted here and here)

GOES-13 Sounder DPI Values of Lifted Index, 1700 UTC on 17 November (click image to enlarge)

GOES-13 Sounder DPI Values of Lifted Index, 1700 UTC on 17 November (click image to enlarge)

Suomi/NPP also viewed the storms, but after they had moved east of Illinois. A toggle between VIIRS Visible, 11.35 µm and 1.61 µm imagery, below, shows isolated supercells pushing through the cirrus shield.

Suomi/NPP Visible (0.65 µm), Infrared (11.45 µm) and 1.61 µm imagery from 1913 UTC 17 November (click to enlarge)

Suomi/NPP Visible (0.65 µm), Infrared (11.45 µm) and 1.61 µm imagery from 1913 UTC 17 November (click to enlarge)

Powerful early October storm: blizzard conditions, and severe thunderstorms

October 5th, 2013
GOES-13 6.5 µm water vapor channel images (click to play animation)

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

An unusually intense (by early October standards) mid-latitude cyclone produced a variety of weather extremes across the parts of the north-central US during the 04 October to 05 October 2013 period. In the cold sector of the storm system, western South Dakota received record-breaking snowfall and prolonged blizzard conditions (NWS Rapid City news story), with widespread power outages and livestock losses being two of the major impacts. The early evolution of the storm could be seen on 4-km resolution GOES-13 6.5 µm water vapor channel images (above; click image to play animation). Surface weather symbols (including precipitation type) are also plotted on the water vapor images. The GOES-13 satellite had been placed into Rapid Scan Operations (RSO) mode during much of this time, providing images as frequently as every 5-10 minutes.

GOES-15 (left) and GOES-13 (right) 0.63 µm visible channel images (click to play animation)

GOES-15 (left) and GOES-13 (right) 0.63 µm visible channel images (click to play animation)

In the warm sector of the storm system, severe thunderstorms produced numerous tornadoes and hail as large as 2.75 inches in diameter (SPC storm reports), primarily across eastern Nebraska into Iowa. A very large tornado produced EF-4 damage in the Wayne, Nebraska area — the development of this storm could be seen on 1-km resolution 0.63 µm visible channel images (above; click image to play animation) and 4-km resolution 10.7 µm IR channel images (below; click image to play animation) from the GOES-15 (GOES-West) and GOES-13 (GOES-East) satellite perspectives. Wayne (station identifier KLCG) is located in the center of the visible and IR images; note that the hourly plotted weather observations for Wayne disappeared after 22 UTC, due to the fact that the airport weather instruments were damaged by the tornado (NWS Omaha news story).

GOES-15 (left) and GOES-13 (right) 10.7 µm IR channel images (click to play animation)

GOES-15 (left) and GOES-13 (right) 10.7 µm IR channel images (click to play animation)

GOES-13 0.63 µm visible channel images with overlays of the corresponding University of Wisconsin GOES-13 IR Cloud Top Cooling Rate (CTCR) product (below; click image to play animation) indicated that CTCR values exceeded 30 degrees Kelvin per 15 minutes (darker blue color enhancement) at 20:45 UTC as the thunderstorm that produced the Wayne tornado was rapidly developing in northeastern Nebraska.

GOES-13 0.63 µm visible images + IR Cloud Top Cooling Rate (click to play animation)

GOES-13 0.63 µm visible images + IR Cloud Top Cooling Rate (click to play animation)

===== 07 October Update =====

High spatial resolution imagery from low Earth orbit (LEO) or “polar-orbiting” satellites can be useful for post-case analysis — with this particular storm, helping to determine the areal coverage of the resulting snowfall, and identifying a tornado damage path.

Suomi NPP VIIRS 0.64 µm visible channel and false-color Red/Green/Blue (RGB) image

Suomi NPP VIIRS 0.64 µm visible channel and false-color Red/Green/Blue (RGB) image

Once the large cloud shield associated with the storm system moved eastward, a comparison of 375-meter resolution (projected onto a 1-km AWIPS grid) Suomi NPP VIIRS 0.64 µm visible channel and false-color Red/Green/Blue (RGB) images from 06 October (above) showed the widespread area of snow cover (which appeared as darker shades of red on the RGB image) over the western third of South Dakota as well as adjacent portions of Wyoming, Nebraska, North Dakota, and Montana. Terrain had an important influence in both the amount and the coverage of snowfall — it is especially interesting to note the areas of bare ground (shades of cyan in the RGB image) immediately downwind (south and southwest) of the Black Hills, where downsloping winds helped keep the precipitation type as rain (AWIPS-2 animation including topography). Aided by upslope flow, as much as 58 inches of snowfall was reported in the northern Black Hills of South Dakota. Note that much of the Black Hills appear darker on the visible and false-color images, due to the high density of coniferous trees — but there was still significant snow cover on the ground.

In addition, a comparison of before (28 September) and after (07 October) 250-meter resolution MODIS true-color RGB images from the SSEC MODIS Today site (below) revealed the southwest-to-northeast oriented damage path from the large tornado which produced EF-4 damage in the Wayne, Nebraska area (NWS Omaha news story).

MODIS true-color RGB images

MODIS true-color RGB images