Using NUCAPS to help nowcast Midwest convection

May 23rd, 2020 |

GOES-16 ABI Band 2 (0.64 µm) visible imagery at 1821 UTC 23 May 2020 (Click to enlarge)

The NOAA Storm Prediction Center’s Convective Outlook (graphic) from 1630 UTC 23 May 2020 shows an enhanced risk of Severe Thunderstorms in northern Illinois with a sharp cutoff in probabilities to the north in southern Wisconsin. The imagery above shows the GOES-16 ABI Band 2 (0.64 µm) visible imagery (click here for Band 13 (10.3 µm) Infrared Imagery), and it shows convection over northern Illinois/southern Wisconsin ahead of an obvious vorticity center in Iowa. How far north will the convection build?

This question can be answered by considering lower-tropospheric (900-700) and mid-tropospheric (850-500) lapse rates diagnosed from the NUCAPS Profiles produced from the NOAA-20 pass over the Upper Midwest at ~1818 UTC (NOAA-20 orbit for this day shown here); these data were available within AWIPS by 1915 UTC! 

The toggle below shows ABI Bands 2 and 13 (0.64 µm and 10.3 µm, respectively) as well as the lapse rates. The Lower Tropospheric lapse rates show a north-south gradient in stability, with air that is more stable over Wisconsin; convection over Illinois should weaken as it moves north. Mid-tropospheric lapse rates show a similar gradient in stability albeit less pronounced. (Click here to view the lower-tropospheric lapse rates overlain with NUCAPS sounding availability points from AWIPS, color-coded to show whether or not Infrared and/or microwave retrievals converged. Over southwest Wisconsin/northwest Illinois, perhaps you can argue that the gradient is influenced by soundings that did not converge; that argument would be harder to make over northcentral/northeast Illinois and southcentral/southeast Wisconsin).

GOES-16 ABI Bands 2 (0.64) and 13 (10.3) at 1821 UTC and Lower- and Mid-Tropospheric Layer Lapse Rates (900-700 and 850-500 mb, respectively) at nominal times of 1818 UTC over the upper Midwest (Click to enlarge)

This post is to remind you that satellite-derived retrieval data (independent of model data) is available in AWIPS in a timely manner to help you diagnose the thermodynamic state of the atmosphere. (Added: Storm reports for this event are here. Severe weather did cross into Wisconsin but was very close to the Illinois border).

Pier 45 Fire in San Francisco

May 23rd, 2020 |

GOES-17 Shortwave Infrared (3.9 µm, top left), GOES-16 Shortwave Infrared (3.9 µm, top right), GOES-17 Near-Infrared "Snow/Ice" (1.61 µm, bottom left) and GOES-17 Near-Infrared "Cloud Particle Size" (2.24 µm, bottom right) [click to enlarge]

GOES-17 Shortwave Infrared (3.9 µm, top left), GOES-16 Shortwave Infrared (3.9 µm, top right), GOES-17 Near-Infrared “Snow/Ice” (1.61 µm, bottom left) and GOES-17 Near-Infrared “Cloud Particle Size” (2.24 µm, bottom right) [click to enlarge]

The thermal signature of a large nighttime fire at Pier 45 in San Francisco (media report) was evident in Shortwave Infrared (3.9 µm) images from GOES-17 (GOES-West) and GOES-16 (GOES-East) — the warmest 3.9 µm brightness temperature sensed by GOES-17 was 27.8ºC (at 1151 UTC), while the warmest temperature sensed by GOES-16 was only 14.2ºC (at 1146 UTC).

Note that a faint thermal signature of the fire (pixels exhibiting dim shades of white) was also apparent in GOES-17 Near-Infrared “Snow/Ice” (1.61 µm) and GOES-17 Near-Infrared “Cloud Particle Size” (2.24 µm) images. This is because those two ABI spectral bands are located close to the peak emitted radiance of very hot features such as volcanic eruptions or large fires (below).

Plots of Spectral Response Functions for ABI Bands 5, 6 and 7 [click to enlarge]

Plots of Spectral Response Functions for ABI Bands 5, 6 and 7 [click to enlarge]

Just after sunrise, the northward meandering of smoke could be seen in GOES-17 “Red” Visible (0.64 µm) images (below).

GOES-17

GOES-17 “Red” Visible (0.64 µm) images [click to enlarge]

However, a larger-scale view of GOES-17 True Color Red-Green-Blue (RGB) images created using Geo2Grid (below) revealed that filaments of higher-altitude smoke were drifting southward, while the aforementioned low-latitude smoke was drifting more slowly northward.

GOES-17 True Color RGB images [click to play animation | MP4]

GOES-17 True Color RGB images [click to play animation | MP4]

A profile of 12 UTC rawinsonde data from Oakland (below) explained these differences in smoke transport — winds at higher altitudes were stronger, and had a northerly component.

Plot of 12 UTC rawinsonde data from Oakland, California [click to enlarge]

Plot of 12 UTC rawinsonde data from Oakland, California [click to enlarge]