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.

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].

Using NUCAPS and ProbSevere LightningCast to anticipate a line of showers

June 10th, 2022 |
GOES-16 Day Cloud Phase Distinction and Radar Composite Reflectivity, 2001 UTC on 10 June 2022 (click to enlarge)

A weak line of showers moved through southern Wisconsin late in the afternoon of 10 June 2022, as depicted in the 2001 UTC toggle above of NEXRAD Composite Reflectivity and GOES-16 Day Cloud Phase Distinction RGB. What satellite-based products could be used to anticipate that line?

NOAA-20 orbits over the Midwestern United States on 10 June (shown here, from this site) were configured such that NUCAPS profiles over Wisconsin were derived from two consecutive passes. The toggle below shows derived Total Precipitable Water at ca. 1730 and 1930 UTC. Dry air over northeastern Wisconsin is abutted by greater values of total precipitable water over the southern part of the state.

Gridded NUCAPS estimates of Total Precipitable Water for two times on 10 June 2022. NUCAPS Sounding Points are also shown (Click to enlarge)

Data from NUCAPS profiles can also be used to compute various stability indices, including the Total Totals index, which is shown below from the two passes. Note in particular the gradient in the index over southern Wisconsin at 1930 UTC: a corridor of instability is present, and it is focused in that location mostly because of dryer air to the northeast (click here to view 850-mb Mixing Ratio from gridded NUCAPS at 1730 and 1930 UTC). In addition, diagnosed mid-level Lapse Rates (in this case, 700-500 mb) at 1930 UTC (shown below) show values between 7 and 8 oC/km. (Note to AWIPS Users: Gridded NUCAPS Total Totals index values can be accessed via the Product Browser, under ‘Grids’)

Total Totals index, 1751 UTC and 1933 UTC, 20 June 2022 (Click to enlarge)
700-500 mb Lapse Rates, 1930 UTC on 10 June 2022 (click to enlarge)

ProbSevere LightningCast (link) is a forecast aid created to diagnose (from ABI imagery) the probability that a GLM Lightning observation will occur in the next 60 minutes. It can also alert a forecaster to developing convection, because the satellite signatures that suggest lightning might occur in the next 60 minutes often occur before radar observations of convection. The animation below shows LightningCast at 15-minute time steps, from 1800 to 2000 UTC on 10 June. Note how LightningCast keys on the developing line of cumulus long before showers develop (and more than 30 minutes before lightning occurs!)

LightningCast probabilitt readout, 1800 – 2000 UTC on 10 June 2022 (Click to enlarge)

The animation below shows GOES-16 Day Cloud Phase Distinction overlain with Geostationary Lightning Mapper (GLM) Minimum Flash Area (MFA) observations, from 2001 – 2316 UTC. Consider the smallest MFA values (in yellow) to represent vigorous, new updrafts. Larger MFA (green) are more likely in the anvil.

GOES-16 Day Cloud Phase Distinction RGB, and GLM Observations of Minimum Flash Area, 2001 – 2316 UTC on 10 June 2022 (click to enlarge)

NUCAPS and ProbSevere LightningCast added to Situational Awareness for this event.

Some imagery in this Blog Post was created using the NOAA/TOWR-S AWIPS Cloud Instance. Thank you!

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)