ProbSevere results over tidewater Virginia

May 6th, 2014 |
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NOAA/CIMSS ProbSevere superimposed on MRMS radar display over southeastern Virginia. Times as indicated. (Click to enlarge)

 

The Hazardous Weather Testbed (HWT) exercise (Click here for the HWT blog) is ongoing at the Storm Prediction Center.  One of the new products being tested by forecasters is the NOAA/CIMSS ProbSevere product. ProbSevere in the animation above highlighted a cell that produced hail. The AWIPS-2 readout suggests strong vertical growth, and strong glaciation, at 0215 UTC. (The HWT Blog entry on this storm is here) What did the satellite view?

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GOES-13 Visible Imagery (0.63 µm), times as indicated. (Click to enlarge)

Visible imagery, above, from just before sunset, shows nascent convective development east of Lynchburg over southeastern Virginia, and also older convection over the Chesapeake Bay and Delmarva Peninsula. The infrared imagery (10.7 µm), below, shows rapid development of convection over southeastern Virginia after 0000 UTC. The first convective cell, which cell is east of the Outer Banks of North Carolina at 0315 UTC, had cloud-tops that cooled about 12 C in 17 minutes (between 0115 and 0132 UTC); the storm that produced hail, and was warned, had cloud-tops that cooled 20 C in 13 minutes, between 0202 UTC and 0215 UTC. This strong vertical growth contributes to a big increase in the ProbSevere value.

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GOES-13 Infrared Imagery (10.7 µm), times as indicated. (Click to enlarge)

When interpreting the radar and satellite imagery, be aware of the effects of parallax on the satellite imagery. GOES-13 imagery displayed here is not corrected for parallax. GOES-13 data are parallax-corrected when used in ProbSevere computations, of course.

NOAA/CIMSS ProbSevere Performance during Tornadic Outbreak

April 27th, 2014 |

Severe weather occurred over the southern Plains/lower Mississippi Valley on Sunday 27 April 2014 (SPC storm reports | GOES-13 IR image animation). How did the NOAA/CIMSS ProbSevere product perform with these storms? Three examples are presented below.

NOAA/CIMSS ProbSevere estimates the likelihood that a growing convective storm will first produce severe weather within the next sixty minutes. The Product uses Rapid Refresh model environmental parameters (Most Unstable CAPE, and Environmental Shear), satellite (GOES-13 only, at present) observations of cloud growth and glaciation, and MRMS radar estimates of Maximum Expected Size of Hail (MESH). A convective tower that grows rapidly (as observed by satellite), for example, will be more likely to spawn severe weather in the next 60 minutes than one that grows more slowly. Similarly, as radar intensities increase, so too do the probabilities. The goal of this product is to increase the lead time for a warning by up to several radar scans.

MRMS Radar and ProbSevere readouts, 21:10, 21:22 and 22:08 UTC on 27 April 2014 [Click to enlarge]

MRMS Radar and ProbSevere readouts, 21:10, 21:22 and 22:08 UTC on 27 April 2014 [Click to enlarge]

The image above shows the radar at 21:10, 21:22 and 22:08 UTC, and also values used in the computation of the ProbSevere product, for a hail-producing storm just south of Dallas. The readout shows the most unstable CAPE and Environment Shear (averaged within the radar object that is outlined), the maximum satellite growth and the maximum glaciation rate that the radar object experienced, and also the MESH. In this case, MUCAPE is 4300-4400 J/kg and Environmental Shear is around 50 kts. The maximum satellite growth for the object being tracked is 1%/minute (% meaning percent of the depth of the troposphere) measured at 20:15 UTC (a time when the radar may or may not have been detecting the developing storm). This moderate growth rate stays attached to this growing convective feature at later times. The ProbSevere exceeded 50% at 21:10 UTC, the first warning was issued at 21:22 UTC and the first report of 1″ hail was at 21:45 UTC. (This storm later produced baseball-sized hail). The storm had moderate growth rates, but very large values of MUCAPE and Shear enhanced the probabilities. Glaciation Rate is reported as N/A, which typically means development under a pre-existing cirrus shield.  That was the case over Dallas, as shown in this animation of visible imagery from GOES-13.

As above, but at 21:20, 21:30 and 22:14 UTC 27 April 2014 [Click to enlarge]

As above, but at 21:20, 21:30 and 22:14 UTC 27 April 2014 [Click to enlarge]

The storm above, over northwestern Mississippi, showed strong satellite growth rates (2.4% per minute) and strong glaciation rates. Probabilities exceeded 50% at 21:14 UTC (just before the 21:20 UTC image shown above) and the first warning was issued at 21:30 UTC, with the first report at 22:31 UTC. This storm produced hail, wind and a tornado.

As above, but at 23:00, 23:08, 23:20 and 23:26 UTC 27 April 2014 [Click to enlarge]

As above, but at 23:00, 23:08, 23:20 and 23:26 UTC 27 April 2014 [Click to enlarge]

A third storm that affected the Kansas City metropolitan area is shown above. ProbSevere exceeded 50% at 23:00 UTC, the first warning was issued at 23:26 UTC and the first hail report occurred 23:31 UTC. Satellite growth for this storm is initially strong (1.5% per minute at 21:25 UTC), but the tracked object linked to that strong growth eventually were lost (Satellite Growth values were lost at 23:20 UTC) and probabilities decrease slightly; they remain relatively high because of the favorable environment and radar observations.

For all three examples above, the probabilities were highest with the convective system that produced the severe weather. The combination of the three components (Rapid Refresh, Radar, and Satellite) is key to the probability. Each individual component has strengths but the combination of predictors is what yields a skillful model with meaningful lead-time.



Severe weather continued on April 28th, including fatal storms in Mississippi.  The image below, however, is for a thunderstorm that formed in Missouri outside the region of SPC’s Slight Risk issued at 1300 UTC, and near the edge of the Slight Risk issued at 1630 UTC.

As above, but at 17:20, 17:22, 17:26 and 17:38 UTC 28 April 2014 [Click to enlarge]

As above, but at 17:20, 17:22, 17:26 and 17:38 UTC 28 April 2014 [Click to enlarge]

The ProbSevere for the developing cell is 24% at 17:20 UTC, with Strong Normalized Vertical Growth Rate (2.3%/min) and weak glaciation (0.01/min) observed at 1655 UTC. At 17:22 UTC, new satellite observations have been incorporated (from the 17:15 UTC scan): the Normalized Vertical Growth Rate is now 3.4%/min; in addition, Glaciation (0.17/Min) is also now strong. As a result, ProbSevere increases to 73%. The Severe Thunderstorm Warning was issued 15 minutes later, at 17:37 UTC, 2 minutes after the first report of severe hail with this storm (in Holts Summit MO, in Callaway County).

 

The ProbSevere product will be evaluated at the Hazardous Weather Testbed to be held in Norman OK in May.

 

Tornado outbreak in Iowa

July 19th, 2018 |

GOES-16 Upper-level Water Vapor (6.2 µm, top left), Mid-level Water Vapor (6.9 µm, top right), Low-level Water Vapor (7.3 µm, bottom left) and

GOES-16 Upper-level Water Vapor (6.2 µm, top left), Mid-level Water Vapor (6.9 µm, top right), Low-level Water Vapor (7.3 µm, bottom left) and “Red” Visible (0.64 µm, bottom right) images [click to play MP4 animation]

GOES-16 (GOES-East) Upper-level Water Vapor (6.2 µm), Mid-level Water Vapor (6.9 µm), Low-level Water Vapor (7.3 µm) and “Red” Visible (0.64 µm) images (above) revealed the well-defined signature of a mid-tropospheric lobe of vorticity moving from southeastern South Dakota across Iowa during the day on 19 July 2018 — this feature provided synoptic-scale forcing for ascent which aided in the development of severe thunderstorms in central and eastern Iowa. A number of tornadoes were reported, along with some large hail and damaging winds (SPC storm reports).

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GOES-16 “Red” Visible (0.64 µm) images, with SPC storm reports plotted in red [click to play MP4 animation]

A closer look using 1-minute Mesoscale Domain Sector GOES-16 “Red” Visible (0.64 µm) images (above) showed the line of thunderstorms as they developed in advance of an approaching cold/occluded front (surface analyses). Two larger storms were dominant, which produced tornadoes causing significant damage and injuries in Pella KPEA and Marshalltown KMIWabove-anvil cirrus plumes were evident with both of these supercells. In addition, early in the animation a few orphan anvils could be seen along the southern end of the line (southeast and east of Des Moines KDSM).

The corresponding GOES-16 “Clean” Infrared Window (10.3 µm) images (below) showed cloud-top infrared brightness temperatures of -65ºC to -70ºC with the larger Pella storm, and around -55ºC with the smaller Marshalltown storm to the north.

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GOES-16 “Clean” Infrared Window (10.3 µm) images, with SPC storm reports plotted in red [click to play MP4 animation]

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GOES-16 “Clean” Infrared Window (10.3 µm) image, with ProbSevere contour and parameters [click to enlarge]

The NOAA/CIMSS ProbSevere model (viewed using RealEarth) had a ProbTor value of 74% at 2055 UTC for the Pella storm (above) and 83% at 2130 UTC for the Marshalltown storm (below). GOES-derived Cloud-top glaciation rate (from infrared imagery) is one of the predictors used in the model.

GOES-16 Infrared image, with ProbSevere parameters [click to enlarge]

GOES-16 “Clean” Infrared Window (10.3 µm) image, with ProbSevere contour and parameters [click to enlarge]

ProbSevere time series plots for the Pella and Marshalltown cells are shown below. They indicated that the Pella storm was long-lived, persisting past 0300 UTC — and that ProbTor ramped up quickly and then down quickly, bracketing the time of the tornado in Marshalltown.

NOAA/CIMSS ProbHail (Green), ProbWind (Blue) and ProbTor (Red) for the cell that produced the Pella IA tornado. [click to enlarge]

NOAA/CIMSS ProbHail (Green), ProbWind (Blue) and ProbTor (Red) for the cell that produced the Pella IA tornado [click to enlarge]

NOAA/CIMSS ProbHail (Green), ProbWind (Blue) and ProbTor (Red) for the cell that produced the Marshalltown IA tornado [click to enlarge]

A toggle between 375-meter resolution Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images at 1946 UTC (below) provided a look at the early stage of development of tornado-producing convection.

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images, with plots of SPC tornado reports within +/- 30 minutes of the images [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images, with plots of SPC tornado reports within +/- 30 minutes of the images [click to enlarge]

Additional satellite imagery and analysis of this event can be found on the Satellite Liaison Blog.


Strong Thunderstorms move through Washington DC.

May 14th, 2018 |

GOES-16 ABI Channel 13 “Clean Window” (10.3 µm) at 1-minute time-steps from 1607-2359 UTC on 14 May 2018 (Click to animate)

A GOES-16 Mesoscale Sector produced 1-minute imagery as a strong thunderstorm complex approached Washington DC late in the afternoon/early evening of 14 May 2018.  The (150-megabyte (!!)) animated gif above shows overshooting tops quickly developing and decaying as the complex moved over the Potomac Basin.  Winds in excess of 60 knots were reported around the Washington DC metropolitan area, with widespread tree damage. (Smaller MP4 animations with plots of SPC storm reports are also available: Infrared | Visible)

NOAA/CIMSS ProbSevere All Hazards (Source), below, showed very high ProbHail and ProbWind with this cell as it approached Washington DC.

NOAA/CIMSS ProbSevere All Hazards, 2200 UTC on 14 May 2018 (Click to enlarge)

GOES-16 Geostationary Lightning Mapper (GLM) data from Real Earth (Link for animation), below, shows an increase in electrical activity to the storms as they moved through Washington DC.

CONUS Hybrid Radar Reflectivity overlain with GLM observations, 2200-2330 UTC 14 May 2018 with 15-minute timestep.