Using the Night Microphysics RGB and LightningCast probabilities to anticipate nighttime convection and Lightning

May 11th, 2022 |
Nighttime MIcrophysics RGB, 0616 – 0811 UTC on 11 May 2022 (click to enlarge)

The Nighttime Microphysics RGB, above, over central Wisconsin (that’s Green Bay at the northeastern edge, and southeast Minnesota/northeast Iowa over the southwestern part, of the animation), shows a field of low clouds stretching west-southwest to east-northeast. Note however, the occasional appearance of redder pixels within the field (as shown in this annotated image from 0806 UTC), especially in Wood and Portage counties (Click here for a map of Wisconsin counties). That kind of signal suggests that vertical cloud growth is occurring. Do you think convection will occur shortly? What about lightning?


NOAA-20 overflew this region shortly after 0730 UTC, and NUCAPS profiles would have become available in AWIPS at about the time of the end of the animation. What do they show? The image below shows 850-mb Temperature and the 850-500 mb lapse rates computed from gridded NUCAPS fields. The steepest lapse rates and strongest instability is centered on a NUCAPS profiles in central WI (in Adams County) which is just south of the band of clouds identifiable in the Night Microphysics RGB shown above: NUCAPS profiles show ample instability just south of this line (and winds are southerly: 0000 UTC Green Bay sounding).

850-mb Temperatures, 850-500 mb Lapse Rate, and Total Totals Index, 0730 UTC on 11 May 2022 (click to enlage)

The individual NUCAPS soundings in Adams County and Green Lake County, below, show very steep mid-level lapse rates.

NUCAPS Profiles in Adams County (left) and Green Lake County (right) at 0735 UTC on 11 May 2022 (Click to enlarge)

The GOES animation of Nighttime Microphysics above ended at 0811 UTC. What happened in the next 15 minutes? Note a continued development in the amount of reddish pixels! During these 15 minutes, radar is also showing increasing returns.

Nighttime Microphsyics RGB, 0811-0826 UTC on 11 May 2022 (Click to enlarge)

If convection is expected, lightning might also occur. Lightning Cast is a product in the NOAA/CIMSS ProbSevere portfolio, and it’s available online here, and a short training video is here. LightningCast probabilities for the same 15-minute span as above are shown below. Low probabilites are present until 0826 UTC. When do you think lightning might occur with this developing line?

LightningCast probabilities, 0811-0826 UTC on 11 May 2022 (click to enlarge)

The animation below follows the developing cells through the next 15 minutes — from 0826 to 0841 UTC. Nighttime Microphysics (overlain by radar: note the parallax shift, and also note the continued reddening of pixels in the RGB where convection is occurring) is on the left, and LightningCast Probabilities are on the right. Do you think lightning is imminent?

Nighttime Microphysics RGB overlain with 0.5 Base Reflectivity (left) and LIghtningCast Probability (right), 0826 – 0841 UTC (Click to enlarge)

The first GLM observations (with a CONUS time cadence of every 5 minutes) of lightning occurred at 0846 UTC, as shown in the animation of the Nighttime Microphysics RGB below. (Here is LightningCast at 0846 UTC).

Nighttime Microphysics RGB and GLM Flash Extent Density (FED), 0616 – 0851 UTC on 11 May 2022 (click to enlarge)

The animation below shows the NightMicrophysics RGB overlain with LightningCast Probabilities, from 0816 to 0846 UTC.

GOES-16 Nighttime Microphysics RGB with LightningCast Probabilities and GLM FED observations, 0816 – 0846 UTC on 11 May 2022 (click to enlarge)

Gridded NUCAPS fields for this blog post were created using the NOAA/TOWR-S Cloud Instance of AWIPS. Thank you! And here is a link to a presentation detailing how the Nighttime Microphysics RGB can be used in winter!

Bolt out of the blue

May 10th, 2022 |

Florida is one of the lightning capitals of the world, so residents need to be constantly aware of lightning safety. NOAA/CIMSS LightningCast might be able to help with that.

A tree and home in Sebring, Florida were suddenly struck by lightning on the morning of Saturday, May 7th. A line of storms was edging its way eastward. A neighbor who was outside at the time said, “It wasn’t raining. It was nice and warm. It was cloudy, but that was it. And then boom!” This underscores how easy it is to be caught unaware of potential lightning danger.

LightningCast can help with users’ situational awareness. LightningCast is an experimental deep-learning model trained on thousands of GOES-R ABI and GLM images to predict the probability of next-hour lightning occurrence. In the animation below, the red dot is Sebring, Florida.

LightningCast probability contours, GOES-16 ABI imagery (grayscale background), and GOES-16 GLM flash-extent density (shaded color). The red dot is the approximate location of the “bolt out of the blue”.
Florida homeowner stunned by nearby lightning strike. Credit: FOX13 Tampa Bay

Below is a time series of LightningCast probability and GLM observations around the home in Sebring. Lightning struck the tree and home at 8:21 EDT, marked by the vertical black line below. You can see a rapid increase in probability of lightning from 11:26 to 11:36 UTC (7:26 to 7:36 EDT), reaching 70%. This was about 25 minutes before the first nearby lightning strike and 45 minutes before the Sebring home was struck.

The animation below from the National Weather Service lightning safety page shows that most lightning casualties occur before a thunderstorm is fully overhead, or before it fully departs the area, when people might not realize their vulnerability to lightning and don’t seek shelter soon enough or leave shelter too soon.

Animation depicting the threat of lightning casualties as a function of a hypothetical storm moving into the area.

Hail in Portland OR

May 9th, 2022 |
GOES-17 Visible Band 2 (0.64 µm) imagery, 2201 UTC 8 May 2022 – 0311 UTC 9 May 2022 (Click to enlarge)

Here’s a text received late on 8 May from a kid: “Hail today in Portland”. The animation above shows GOES-17 Visible (0.64 µm) imagery between 2201 UTC on 8 May and 0311 UTC on 9 May. The follow-up text answering the obvious question (What time?) was “Around 5 PM” — that is, around 0000 UTC on 9 May. Infrared imagery (Band 13, 10.3 µm) from GOES-17 over the same time period — 2201 – 0311 UTC — is shown below. This loop uses a default enhancement from AWIPS (which enhancement has as its coolest temperature -109oC, perhaps too cold for this airmass; click here to see an animation with a coolest temperature of -90oC; variability in the cold cloud tops is much easier to visualize in that modified color enhancement).

GOES-17 Infrared Band 13 (10.3 µm) imagery, 2201 UTC 8 May 2022 – 0311 UTC 9 May 2022 (Click to enlarge)

The slower animation below, between 0000 UTC and 0100 UTC, highlights the cold cloud tops (west of Portand) of the system that might have produced hail. The eye is drawn to the developing cold cloud tops with the tweaked (non-default) enhancement. (By this time, having examined the imagery, I wonder about the report of the hail occurring around 5 PM; This event was also mentioned on the NWS Portland Facebook page).

GOES-17 Visible Imagery (left), Infrared (center, with default enhancement) and infrared (right, with a smaller range to the enhancement), 0000-0100 UTC on 9 May 2022 (click to enlarge)

LightningCast Probability is a product in the NOAA/CIMSS ProbSevere portfolio that predicts the likelihood of a GLM Flash Event based on a single time of the GOES-17 bands that are used in the Day Cloud Phase Distinction RGB: Bands 2 (0.64 µm), 5 (1.61 µm) and 13 (10.3 µm). The animation of that field is shown below. Contours denote probabilities of 10% (dark blue), 25% (cyan), 50% (green) and 75% (magenta). One lightning flash is shown at the of the animation; note however how the probability contours center on the strongest developing convective cell early in its lifecyle — even though it never produced lightning as detected by the GOES-17 GLM.

LightningCast Probability, 2335 UTC on 8 May 2022 – 0100 UTC on 9 May 2022 (click to enlarge)

NOAA-20 overflew the Pacific Northwest in the afternoon, with two passes over Oregon, as shown in the toggle below that also shows gridded 850-500 mb NUCAPS Lapse Rates at 1933 and 2113 UTC on 8 May. Even though the westernmost NOAA-20 has truncated data, very steep lapse rates — near 8o C/km — are evident.

Gridded 850-500 mb Lapse Rates, 1933 and 2115 UTC on 8 May 2022 (click to enlarge)

500-mb temperatures are shown below, with Portland deep within the cold air (500-mb temperatures are at/below -30o C!). The gridded fields look smooth despite the abundance of yellow and red points in the NUCAPS fields, designating regions where the infrared retrieval did not converge (yellow) or where the infrared and microwave retrievals both failed! This example shows that profiles that do not converge because of low-level clouds/moisture/rain may nevertheless produce useful upper-air information. The 2113 UTC 500-mb temperature field here, shows a red profile in the Willamette Valley in the northernmost row of profiles, and a green profile in the same row just west of the Oregon Coast. The toggle of profiles at those two points is shown below; both have useful information around 500 mb (and above) even though near-surface values in the red profile are of dubious value. Note the steep lower-tropospheric lapse rates in the sounding that is just offshore!

Gridded 500-mb Temperature derived from NUCAPS profiles, 1933 UTC and 2115 UTC on 8 May 2022 (click to enlarge)
NUCAPS profiles at circled (in black) locations, 2138 UTC on 8 May 2022 (click to enlarge)

NUCAPS imagery was created with the NOAA/TOWR-S AWIPS Cloud instance. Thank you!