Strong Winter Storm over the upper Ohio River Valley with severe weather in the Mid-Atlantic

February 24th, 2016 |
GOES-14 Water Vapor Infrared (6.5 µm) images [click to play mp4 animation]

GOES-14 Water Vapor Infrared (6.5 µm) images [click to play animation]

A strong winter storm produced a swath of winter weather from Arkansas through lower Michigan on 23-24 February. GOES-14 SRSO-R Imagery was centered on the occluded storm on 24 February, and the water vapor animation, above (available here as an animated gif image), shows strong flow north-northwest from the Mid-Atlantic states into the Upper Midwest, where Winter Storm and Blizzard Warnings were widespread. The end of the animation shows strong convection developing over the Mid-Altantic states where multiple reports of Severe Weather occurred. (A water vapor animation with weather symbols included is available here as an mp4 and here as an animated gif).

Rapid Refresh Model Simulation of 310 K Equivalent Potential Temperature Surface [click to play animation]

Rapid Refresh Model Simulation of 310 K Equivalent Potential Temperature Surface [click to play animation]

The thermal structure of the storm as revealed by Rapid Refresh analyses of the 310 Kelvin Equivalent Potential Temperature Surface, above, (and available here with contours of Mean Sea Level Pressure) suggests the presence of a Trough of Warm Air Aloft (TROWAL) that stretches from Tennessee to Michigan. Any dry air that moves northward over this region is likely to eroded from below as low-level moisture (not detected in the water vapor imagery) is forced upwards by frontogenetic circulations along the sloping isentropes. Note how cold cloud tops in the animation above appear with regularity over southern Michigan and northern Indiana. These cold clouds tops in the water vapor imagery could be manifestations of frontal forcings acting on the warm air in the TROWAL airstream. Simulated ABI Water Vapor Channels (available here or here), below, show the blossoming of cold cloud tops in the 7.3 µm channel. This toggle between the 6.2µm and 7.3µm channels at 2100 UTC shows how the different water vapor channels view different levels in the atmosphere because of different sensitivity to water vapor absorption at those two wavelengths: the 7.3µm channel typically sees deeper into the troposphere and therefore has warmer brightness temperatures.

Simulated ABI 7.3 µm Water Vapor Channel Imagery, hourly from 16-22 UTC on 24 February 2016 [click to play animation]

Simulated ABI 7.3 µm Water Vapor Channel Imagery, hourly from 16-22 UTC on 24 February 2016 [click to play animation]

GOES-13 Visible (0.65 µm) images [click to play animation]

GOES-13 Visible (0.65 µm) images [click to play animation]

When storms move north to the west of the spine of the Appalachians, downslope winds frequently cause clearing, and this occurred on 24 February, as shown in the half-hourly animation of GOES-13 Visible imagery above. Clear skies are widespread over southeastern Ohio and southwestern Pennsylvania. Cities in the region that cleared saw high temperatures in the mid-60s today. The visible imagery above shows evidence of strong shear in the warm sector (where SPC had issued a Moderate Risk). GOES-14 1-minute Visible Imagery for the 30 minutes ending at 2230 UTC, available here, shows a line of strong convection from the Piedmont of North Carolina northward to metropolitan Washington DC.

GOES-14 Visible (0.65 µm) images [click to play animation]

GOES-14 Visible (0.65 µm) images [click to play animation]

Visible SRSO-R Imagery from GOES-14, above, shows the strong storms moving rapidly to the northeast along a line stretching from Washington DC south to central North Carolina as the sun set on 24 February. (Animation available here as an mp4). Another animation of GOES-14 visible images centered on Virginia and North Carolina (covering the period from 1300-2159 UTC) with plots of station identifiers is available as an MP4 or an animated GIF.


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NOAA/CIMSS ProbSevere output superimposed on MRMS Merged QC Composite Reflectivity, times as Indicated [click to play animation]

NOAA/CIMSS ProbSevere output superimposed on MRMS Merged QC Composite Reflectivity, times as Indicated [click to play animation]

The NOAA/CIMSS ProbSevere model combines information about the storm environment (from the Rapid Refresh) with satellite indicators of cloud growth and with radar estimates of hail size. It is designed to predict when a developing convective cell will first produce severe weather. In the animation above, a growing cell has developed over South Carolina. At the start of the animation, 2134 UTC, the cell is displaying moderate growth rate, and weak glaciation. Two minutes later, at 2136 UTC, ProbSevere has jumped to 62% as the MRMS MESH (Maximum Expected Size of Hail) has jumped from 0.32 to 0.67 inches. By 2144 UTC, ProbSevere exceeds 90%, and it retains that value through the end of the animation at 2250 UTC. This cell produced wind damage three miles northwest of Brownsville SC at 2130 UTC. (SPC Storm Reports). The cell was associated with other wind events in Robeson County, NC at 2155 UTC.

NOAA/CIMSS ProbSevere with a Nebraska Hailstorm

September 22nd, 2015 |
GOES-13 Visible (0.63 µm) images [click to play rocking animation]

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

A severe hail-producing thunderstorm moved over northeast Nebraska before noon on 22 September (SPC Storm Reports). The region hit was just south of a Marginal Risk of Severe Weather (The update at 1630 UTC included the region of severe weather). The GOES-13 visible animation, above, shows the initial development occurring along a subtle cloud line aligned mostly east-west.

The NOAA/CIMSS ProbSevere model produces a probability that a developing thunderstorm will initially produce severe weather within the next sixty minutes. It consistently supplies information with a good lead time, and the storm on 22 September was no exception. The animation below shows the product for about an hour before the first storm report at 1408 UTC. The storm out of which the hail dropped was, at 1300 UTC, flagged as having a ProbSevere under 10%; values exceeded 10% at 1314 UTC and then jumped to 60+% at 1336 UTC (the first time that the value exceeded 50%) Values fluctuated between 60 and 80% between 1336 and 1400 UTC. After 1400 UTC, values increased into the mid-80s. The first report of hail was at 1408 UTC, 32 minutes after ProbSevere jumped above 50%. A severe thunderstorm warning for hail was issued at 1412 UTC.

NOAA/CIMSS ProbSevere values, 1300-1412 UTC on 22 September 2015 [click to play animation]

NOAA/CIMSS ProbSevere values, 1300-1412 UTC on 22 September 2015 [click to play animation]

The GOES Sounder Lifted index product, below, (also available here) showed the instability that was present over the central Plains.

GOES-13 Sounder DPI Values of Lifted Index [click to play animation]

GOES-13 Sounder DPI Values of Lifted Index [click to play animation]

Tornadic Thunderstorm over eastern Colorado

May 28th, 2015 |

NOAA/CIMSS ProbSevere Product, 1902-1922 UTC on 27 May 2015 [click to play very very large animation]

GOES-14 Visible Imagery (0.626 µm) animation, 1708 UTC 27 May 2015 – 0059 UTC 28 May 2015 [click to play very very large animation]

A tornado was reported near Yuma, CO, (SPC Storm Reports) at 1910 UTC on 27 May 2015. GOES-14 was in SRSO-R scanning mode, and a storm-centered animation of the visible imagery (0.626 µm) is shown above (Warning: the animation above is 270M; click here for an mp4, or view it on YouTube). Note that GOES-14 produces no imagery from 1900-1915 UTC when the satellite is performing daily station-keeping maneuvers. The tornado occurred early in the life of the supercell on which the animation centers.

The NOAA/CIMSS ProbSevere output for this storm is shown below. ProbSevere increased above 50% at 1904 UTC. The satellite information for the storm object was derived from GOES-13 data between 1730 and 1745 UTC, when strong growth occurred, and from 1745-1815 UTC when weak glaciation occurred (how the reduced time resolution at that time, when GOES-13 is scanning a full-disk image, affected the Glaciation estimates is not certain — ‘weak’ is probably a lower bound).

NOAA/CIMSS ProbSevere Product, 1902-1922 UTC on 27 May 2015 [click to play animation]

NOAA/CIMSS ProbSevere Product, 1902-1922 UTC on 27 May 2015 [click to play animation]

GOES-14 SRSO Imagery over Texas

May 20th, 2015 |
GOES-14 0.62 µm visible imagery; Andrews County is highlighted [click to play animation]

GOES-14 0.62 µm visible imagery; Andrews County is highlighted [click to play animation]

GOES-14, in SRSO-R mode, animation, above (YouTube video), captured the development of an isolated cell over northeastern Andrews County in west Texas. Intersecting boundaries helped force the isolated convection, above, that was strong enough to produce a signal in the NOAA/CIMSS ProbSevere product, with ProbSevere peaking at around 15%.

NOAA/CIMSS ProbSevere output, 1400 UTC on 20 May 2015 [click to enlarge

NOAA/CIMSS ProbSevere output, 1400 UTC on 20 May 2015 [click to enlarge]