Turbulence on a flight from Tampa to Nashville

July 20th, 2022 |
GOES-16 True Color imagery from 1841 – 1956 UTC on 20 July 2022 (Click to enlarge)

An Embraer 175L took off from Tampa shortly before 1900 UTC on 20 July 2022. About an hour into the smooth flight (as shown here, i.e., around 1945-1950 UTC), turbulence injured about 7 passengers that resulted in a diversion to Birmingham AL (news article; Here is the flight path). The animation of true-color imagery, above, taken from the CSPP Geosphere site (link), shows the region of turbulence, a region of strong convection developing west-to-east along a boundary just inland from Gulf Coast from Mississippi to Florida.

The CIMSS Turbulence site (link) shows probabilities of Moderate-of-Greater (MOG) Turbulence. This machine-learning product was developed using satellite imagery and NOAA/NWS Global Forecasting System (GFS) model output as well as observations of Eddy Dissipation Rate (EDR) on board large aircraft (Here is a training video on the product). MOG Probability fields over North America — along with EDR observation points and Pilot Reports of turbulence — from 1750 to 2140 UTC on 20 July 2022.

MOG Turbulence probabilities, 1740 – 2140 UTC on 20 July, along with Pilot Reports (PIREPs) of turbulence (Click to enlarge)

The CIMSS turbulence site also includes a Midwest sector that shows the Gulf Coast region; MOG Probability contours and observations are revealed for this event with more clarity. The turbulence was observed in between two different regions of higher probability. This matches an observed feature of this product as noted in the training: We notice that often turbulence occurs on the edge of a predicted feature, not in the center. This indicates that an aircraft that skirts just around a known feature is not “in the clear”. That was the case on this day.

MOG Turbulence Probabilities, along with Pilot Reports (PIREPs) of turbulence and EDR observation points, 1920 – 2000 UTC on 20 July 2022 (Click to enlarge)

Using SAR Winds to center-fix Tropical Cyclone Estelle in the Eastern Pacific

July 20th, 2022 |
OGES-17 Visible (Band 2, 0.64 µm) and Infrared (Band 13, 10.3 µm) at 0150 UTC on 20 July 2022 (click to enlarge)

GOES-17 visible and infrared imagery shows Tropical Storm Estelle over the eastern Pacific to the west-southwest of Baja California. Although there are regions of strong convection, satellite presentation of the storm suggests a modest tropical storm. Center-fixing a storm such as this (with just one image vs. an animation!) is complicated by both parallax (GOES-17 is overhead at 0oN, 137.2oW) and the lack of an easily-discerned eye feature in this system.

Instruments that view surface winds, via Scatterometry or via Synthetic Aperture Radar (SAR), can offer better center fixes. Consider the toggle below of Radarsat-2 SAR winds over Estelle. SAR Winds (available here; SAR winds over Tropical Systems can be found here.) show a lopsided storm, with most of the strong winds on the poleward side of the center. The SAR winds that use 0.5-degree GFS wind data as a first guess show a characteristic hourglass feature near the center that advertises an ambiguity between the first guess winds and the observations. That feature is missing in the SAR wind field that is a product of the 0.25-degree GFS winds, suggesting that the 0.25-degree wind field is more accurate. Both fields show a rather baggy center at or just south of 20oN.

RSAT-2 SAR Winds over Estelle benchmarked by 0.5-degree and 0.25-degree model output, 0150 UTC on 20 July 2022; note the different color scales used in the two images (Click to enlarge)

Scatterometry from MetopB and HY2B between 1730 UTC 19 July and 0230 UTC 20 July, respectively show a storm moving west-northwest, passing north of 20oN just after 0230 UTC.

ASCAT (MetopB) and HY2B Scatterometry winds at 1730 (19 July) and 0230 (20 July), respectively.