The Use of GOES-16 Satellite Data for Nowcasting Convection over the Southeastern United States

Frank Alsheimer, NOAA/NWS Columbia, SC

Southeastern United States Climate

• Roughly between 25-35N Latitude and 75-90 W Longitude.

• Mild winters, hot and humid summers.

• Prone to severe convection all seasons.

Two Different Severe Convective Cases

• A mid-summer case with high instability but low shear.

• A spring case with moderate instability and strong shear.

• Look at specific nowcasting challenges

– Initiation

– Maintenance

– Severity

Case 1: July 7th 2017

A typical summer convective forecast day in the southeastern United States (July 7, 2017).

• Moderate/High amounts of Convective Available Potential Energy (CAPE) during maximum diurnal heating (2000-3000 J/kg)

• Little to no wind shear or synoptic scale forcing for convective initiation and maintenance.

• Initiation time/location and potential severity (wind damage, hail, tornadoes) are difficult forecast challenges due to lack of organization.

Case 1: July 7th 2017

• Using GOES-East

– Cloud and Moisture Imagery (CMI)

– Channel Difference Products

– Baseline Products

– RGBs

July 7, 2017 (15Z, MSLP)

Afternoon high temperatures 90-99°F (32-37°C) Afternoon dew points 70-75°F (21-24°C) Not a front or low to be found in the area.

July 7, 2017 (12Z, 500 hPa)

GOES-16 ABI Visible/Near-IR Bands

Band Central Wavelength (µm) Nickname Type Nominal subsatellite

IGFOV

1 0.47 "Blue" Band Visible 1 km

2 0.64 "Red" Band Visible 0.5 km

3 0.86 "Veggie" Band Near-IR 1 km

4 1.37 "Cirrus" Band Near-IR 2 km

5 1.6 "Snow/Ice" Band Near-IR 1 km

6 2.2 "Cloud Particle Size"

Band Near-IR 2 km

Visible “Red” Band 2 (0.64µm) 1337-1612Z

GOES-16 ABI Bands (all 2 km IGFOV) Band

Central Wavelength (µm)

Nickname

Type

7 3.9 "Shortwave Window" Band IR (with reflected

daytime component)

8 6.2 "Upper-Level Tropospheric

Water Vapor" Band IR

9 6.9 “Mid-Level Tropospheric Water

Vapor” Band IR

10 7.3 “Lower-level Water

Vapor” Band IR 11 8.4 "Cloud-Top Phase" Band IR

12 9.6 "Ozone Band" IR

13 10.3 "Clean" IR Longwave

Window Band IR

14 11.2 IR Longwave Window Band IR

15 12.3 "Dirty" Longwave Window

Band IR

16 13.3 "CO2" longwave infrared IR

Low-Level WV Band 10 (7.3µm) 1337-1612Z

GOES-16 ABI Bands (all 2 km IGFOV)

Band

Central Wavelength (µm)

Nickname

Type

7 3.9 "Shortwave Window" Band IR (with reflected

daytime component)

8 6.2 "Upper-Level Tropospheric

Water Vapor" Band IR 9 6.9

“Mid-Level Tropospheric Water

Vapor” Band IR

10 7.3 “Lower-level Water

Vapor” Band IR

11 8.4 "Cloud-Top Phase" Band IR

12 9.6 "Ozone Band" IR

13 10.3 "Clean" IR Longwave

Window Band IR

14 11.2 IR Longwave Window Band IR

15 12.3 "Dirty" Longwave Window

Band IR

16 13.3 "CO2" longwave infrared IR

Upper-Level WV Band 8 (6.2µm) 1337-1612Z

GOES-16 ABI Bands (all 2 km IGFOV) Band

Central Wavelength (µm)

Nickname

Type

7 3.9 "Shortwave Window" Band IR (with reflected

daytime component)

8 6.2 "Upper-Level Tropospheric

Water Vapor" Band IR

9 6.9 “Mid-Level Tropospheric Water

Vapor” Band IR

10 7.3 “Lower-level Water

Vapor” Band IR

11 8.4 "Cloud-Top Phase" Band IR

12 9.6 "Ozone Band" IR

13 10.3 "Clean" IR Longwave

Window Band IR 14 11.2 IR Longwave Window Band IR

15 12.3 "Dirty" Longwave Window

Band IR 16 13.3 "CO2" longwave infrared IR

Channel Differences

• Simple subtraction of 2 bands

• Most used in U.S. is for fog/low clouds (10.3µm - 3.9µm)

• Today’s example is 10.3µm – 12.3µm (split window difference) The 12.3 µm band is modestly sensitive to water vapor

The 10.3 µm band has very little sensitivity to water vapor

Therefore, subtracting the two bands allows us to infer moisture

Split Window Difference (10.3-12.3) 1337-1612Z

Baseline Products

Total Precipitable Water

Advantages

• Gives 5 minute update on CONUS scale!

• NWS CAE has found it reliable to within 0.1-0.2 inches (gradients just as important, if not more, than actual readings)

Disadvantage

• Not calculated in cloudy regions (LEO helps fill in GAPS to create blended TPW products).

Vis band 2 and GOES PW 1337-1612Z

So what is…

THE REST OF THE STORY

RGBs (Multispectral Applications) Red, Green, Blue (RGB) consolidates information from different spectral channels into single products.

• More information than one channel alone.

• Different RGB recipes allow features to stand out.

– Convection

– Smoke/Fire

– Ash/Dust

– Air Mass Characteristics

• Two Types

1. Simple

2. Advanced

Air Mass RGB (Adapted From EUMETSAT)

The Air Mass RGB enhances temperature and moisture characteristics of air masses. • Jet Streams • Stratospheric Air Intrusions • Shortwaves • Air Mass Types • Upper Level Moisture Boundaries

Air Mass RGB 1337-0202Z

Air Mass RGB and band 13 (10.3µm) 1337-0202Z

Simple Water Vapor RGB (Adapted from JMA)

The Simple Water Vapor RGB helps discriminate the distribution of atmospheric water vapor. • Low Leve Moisture Return in Absence of Clouds • Cyclone Structure • Jet Features • Convective Initiation • Wave Features (gravity, standing mountain, etc.)

Simple Water Vapor RGB 1337-0202Z

Red Visible (band 2) 1337-0202Z

7/7/17 Warnings and Reports

Storms Approaching CAE (courtesy Chris Jackson)

Case 2: March 19th 2018

A typical spring severe convective forecast event in the southeastern United States.

• Mod/High amounts of CAPE in a smaller area.

• Significant wind shear co-located with higher CAPE.

• Initiation time/location and maintenance are difficult forecast challenges due to timing of forcing mechanisms, as well as potential disruption from other areas of convection.

Surface Analysis 18Z March 19, 2018

Surface-Based CAPE 18Z March 19, 2018

Effective Bulk Shear 18Z March 19, 2018

Effective Storm Relative Helicity 18Z March 19, 2018

18Z Upper Air Sounding, 3/19/18, Birmingham, AL

Red Visible/Clean IR “Sandwich”, 18Z-00Z 3/19/18

Day Cloud Convection RGB

Day Cloud Convection RGB 18Z-23Z 3/19/18

Surface Analysis 00Z March 20, 2018

00Z Upper Air Sounding, 3/20/18 Birmingham, AL

Surface-Based CAPE 01Z March 20, 2018

Effective Bulk Shear 01Z March 20, 2018

Effective Storm Relative Helicity 01Z March 20, 2018

Air Mass RGB/IR 18Z-02Z 3/19-20/18

Simple WV RGB/IR 18Z-02Z 3/19-20/18

Doppler Radar at 0137Z

March 20, 2018 during EF3 tornado at

Jacksonville, AL