ProbSevere LightningCast Probabilities for Guam

September 15th, 2022 |
RealEarth display of Himawari-8 Band 13 (10.4 µm) infrared imagery and LightningCast Probability contours, 1320 – 1420 UTC on 15 September 2022 (Click to enlarge)

At the request of the National Weather Service forecast office in Guam (where the National Weather Service’s day begins), CIMSS is computing a small region of LightningCast Probabilities that uses Himawari-8 data. The Guam forecast office issues a lightning ‘advisory’ if lightning is possible or occurring within 20 mi of the Guam Airport, and a lightning ‘warning’ if lightning is possible/occurring within 5 mi of the airport. LightningCast probabilities will help in this task. Forecasters will be evaluating its performance in the coming weeks.

LightningCast imagery is available in a RealEarth instance here (at that website, there is a small drop-down menu titled ‘Select Sector’; Choose Guam). An example animation is shown above. (Guam is located at the outer fringes of Typhoon Nanmadol in the image) In contrast to the scenes under GOES-East’s and GOES-West’s view, GLM data are not available. In the forecast office, ground-based lightning sources are available. This animation (from John Cintineo, CIMSS) shows LightningCast probabilities with Earth Networks Total Lightning. Animations online, as shown above, show only Himawari-8 data and LightningCast probability contours.

As with GOES-R LightningCast computations, Himawari-8 uses Visible (0.64 µm), near-infrared (1.61 µm) and infrared (10.41 µm and 12.3 µm) observations. Resolution differences at 1.61 µm (1 km for GOES-R and 2 km for Himawari-8) and slight differences in infrared spectral responses, especially for band 13 (centered near 10.33 µm for GOES-R and 10.41 µm for Himawari-8) may have an as-yet unknown impact on LightningCast probabilities.

Tornado in metropolitan DC

July 5th, 2022 |
GOES-16 Band 13 infrared (10.3 µm) imagery, 2001 – 2256 UTC, 5 July 2022 (Click to enlarge)

GOES-16 infrared (above) and visible (below) imagery late in the afternoon of 5 July 2022 show the development of convection in between Baltimore and the District of Columbia. Tornadoes occurred in both Prince George County, just east and north of the District of Columbia, and over Anne Arundel county, just south of Baltimore (SPC Storm reports from 5 July). The storms that spawned these tornadoes (between 2130 UTC and 2200 UTC) developed quickly between DC and Baltimore, with tops cooling to about -55oC. Note that a parallax shift (to the south-southeast, towards the GOES-16 sub-satellite point at 0o N, 75.2o W) should be applied to these images to georeference them properly to the Earth’s surface. The repetitive re-development of cooler cloud tops between DC and Baltimore from 2100 – 2300 UTC suggests some kind of boundary to focus development in that region.

GOES-16 Band 2 infrared (0.64 µm) imagery, 2001 – 2256 UTC, 5 July 2022 (Click to enlarge)

NOAA/CIMSS ProbSevere (v. 3) — available at this website (and in AWIPS at select NWS Offices) was useful for this storm in that it showed highest values with the radar object associated with the tornado, thus conveying information to a forecaster (or radar operator) on which cell to investigate most thoroughly. The radar cell that spawned the tornado consistently had ProbSevere values exceeding 40%, compared to values in the 10-20% range for other radar objects.

ProbSevere (v. 3) display at 5-minute time-steps, 2000 – 2200 UTC on 5 July 2022 (Click to enlarge)

The ProbSevere website includes links to print out time series plots of particular radar objects. For this event, analysis is a bit complicated because the radar object was assigned a new ID value between 2100 and 2105 UTC, perhaps associated with the radar object splitting, as shown in this 2100/2105 UTC toggle, when the radar object was northeast of DC and southwest of Baltimore.

ProbSevere readout for Radar Object #571697, ca. 2000 – 2100 UTC on 5 July 2022 (Click to enlarge)
ProbSevere readout for Radar Object #572387, ca. 2100 – 2300 UTC on 5 July 2022 (Click to enlarge)

ProbSevere (v. 3) on this data gave useful information in highlighting the advanced threat with this particular cell compared to surrounding radar cells.

This event was also written up in the Washington Post (link). (Thanks to my sister for sending me the link!) Severe Thunderstorm warnings with the severe cell were issued at 2055 UTC (expiring at 2145 UTC), and at 2118 UTC (expiring at 2215 UTC); the first tornado warning was issued at 2121 UTC (expiring at 2145 UTC). The cell that produced the tornadoes had a long warning history.

ProbSevere and LightningCast over La Crosse, Wisconsin

June 15th, 2022 |

ProbSevere is a weather product that uses GOES-16 data to help predict the probability of any severe weather (hail, wind, or tornados) happening in the next 60 minutes. ProbSevere LightningCast predicts the probability that a GLM Lightning observation will occur in the next 60 minutes. Below are examples of these products over the Western Wisconsin area as a convective system rolls through La Crosse, Wisconsin.

The ProbSevere probability product imaged as contours, overlayed with GOES-16 Day Cloud Convection RGB for 06-15-2022 from 20:00 to 20:22Z near La Crosse, Wisconsin [Click to enlarge].
The LightningCast probability product imaged as contours of 75, 50, 25, and 10 percent, overlayed with GOES-16 Day Cloud Convection RGB for 06-15-2022 from 20:00 to 20:22Z near La Crosse, Wisconsin [Click to enlarge].

ProbSevere (and NUCAPS) with the Gaylord Tornado

May 20th, 2022 |
ProbSevere Version 3 readout at 5-minute intervals, 1800 – 2030 UTC on 20 May 2022 (Click to enlarge)

ProbSevere (version 3) is an online tool that is available at this link. It gives the probability that the designated radar object will product severe weather in the next 60 minutes, and it was designed to be used in conjunction with other radar, satellite and model data to increase confidence in warning issuance. It is available online here; ProbSevere (version 2) is also online — and available within AWIPS. The RealEarth-based readout, above, shows the radar object that produced the EF-3 Tornado in Gaylord. (Click here for the NWS Gaylord writeup). ProbSevere values were consistently high with the radar object thoughout the trek across the northern Lower Peninsula of Michigan. Here is an image showing the accumulated ProbSevere values across northern Michigan (from this RealEarth link)

Read-outs of PSv3 and PSv2 values are available at this link, and the plot for the radar object in the animation above (#170831) is shown below (Here is a permanent link that allows you to view values!). Of note here is that PSv2 values are larger than PSv3 values. This is because PSv3 is better calibrated. For example, the Gaylord Tornado has a ProbTor value (plotted in red) of 90%! However, it is not the case that ProbTor (version 2) predictions with values of 90% lead to tornadoes 90% of the time: ProbTor v2 is overpredicting values in that case. ProbTor (version 3) is better calibrated, and the lower values are more in line with observations. Users familiar with ProbTor version 2 will need to adjust their expectations when transitioning to ProbTor version 3 (or indeed from any of the ProbSevere version 2 products to ProbSevere version 3 products).

ProbSevere readout for values associated with Object ID# 170381 (click to enlarge)

NOAA-20 overflew the region of severe weather just before 1800 UTC (link). Gridded NUCAPS fields from this site, below, show marked instability over the northwestern Lower Peninsula of Michigan, especially in the 700-500 mb layer, where gridded values exceed 7 C/km. The gridded values also show a decrease in stability for any storms moving into the Lower Peninsula from the west; however, Quality Control flags (shown below in a toggle with 850-mb Temperature), show profiles that did not converge over Lake Michigan.

Gridded NUCAPS Lapse Rates, 850-700 mb. 700-500 mb and 850-500 mb (click to enlarge)
NUCAPS Quality Control Flags (Green: Retrievals converged; Red: Retrievals did not converge; Yellow: Microwave retrieval converged, infrared did not converge) and 850-mb Temperature at 1745 UTC on 20 May 2022 (Click to enlarge)