Tehuano wind event

March 5th, 2019 |

GOES-17 (left) and GOES-16 (right)

GOES-17 (left) and GOES-16 (right) “Red” Visible (0.64 µm) images, with plots of surface wind barbs (speed in knots) [click to play animation | MP4]

After a strong arctic cold front plunged southward across the US, the Gulf of Mexico, and then southern Mexico during the previous two days (surface analyses), GOES-17 (GOES-West) and GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) revealed the hazy plume of dust-laden Tehuano gap wind flow as it emerged from the southern coast of Mexico and spread southwestward across the Gulf of Tehuantepec and the Pacific Ocean on 05 March 2019. An image of the topography of southeastern Mexico shows the location of Chivela Pass, through which these gap winds flow. Along the Gulf of Mexico coast, surface winds gusted to 30 knots and higher after the cold front moved through Minatitlán/Coatzacoalcos International Airport (station identifier MMMT); off the Pacific coast, a ship in the Gulf of Tehuantepec reported a sustained wind speed of 30 knots at 12 UTC.

The GOES-16 Aerosol Optical Depth product (below) showed lightly enhanced AOD values toward the outer edges of the swath of Tehuano winds. Note the gap in the product during the afternoon hours, when large amounts of sun glint were present.

GOES-16 Aerosol Optical Depth product [click to play animation | MP4]

GOES-16 Aerosol Optical Depth product [click to play animation | MP4]

The GOES-16 Dust Detection product (below) did portray Low to Medium-Confidence areas of dust within the gap wind flow.

GOES-16 Dust Detection product [click to play animation | MP4]

GOES-16 Dust Detection product [click to play animation | MP4]

An overpass of the Suomi NPP satellite after 19 UTC provided numerous NUCAPS sounding profiles both within and outside of the perimeter of the Tehuano winds (below).

GOES-16 Aerosol Optical Depth product, with plots of available NUCAPS sounding profiles [click to enlarge]

GOES-16 Aerosol Optical Depth product, with plots of available NUCAPS sounding profiles [click to enlarge]

A comparison between a dry NUCAPS sounding (Point D) where the gap winds were first exiting the coast over the Gulf of Tehuantepec and a more “undisturbed” moist sounding (Point M) northwest of the gap wind flow is shown below. The dry air of the Tehuano wind flow was very shallow, but its presence could be seen in differences between the marine boundary layer dew point profile and the resulting height of the Lifting Condensation Level (LCL).

Comparison of Dry (D) and Moist (M) NUCAPS soundings [click to enlarge]

Comparison of Dry (D) and Moist (M) NUCAPS soundings [click to enlarge]

A NOAA-20 VIIRS True Color Red-Green-Blue (RGB) image viewed using RealEarth (below) also showed the hazy signature of dust-laden air.

NOAA-20 VIIRS True Color Red-Green-Blue (RGB) image [click to enlarge]

NOAA-20 VIIRS True Color Red-Green-Blue (RGB) image [click to enlarge]

===== 06 March Update =====

GOES-16 Shortwave Infrared (3.9 µm) image, with Metop-A ASCAT winds [click to enlarge]

GOES-16 Shortwave Infrared (3.9 µm) image, with Metop-A ASCAT winds [click to enlarge]

GOES-16 Shortwave Infrared (3.9 µm) images with overlays of Metop-A ASCAT winds around 0338 UTC (above) and 1607 UTC (below) revealed a secondary surge of Tehuano winds on 06 March. The highest wind speed at 0338 UTC was 44 knots, with 38 knots being measured at 1607 UTC.

GOES-16 Shortwave Infrared (3.9 µm) image, with Metop-A ASCAT winds [click to enlarge]

GOES-16 Shortwave Infrared (3.9 µm) image, with Metop-A ASCAT winds [click to enlarge]

GOES-16 Shortwave Infrared images (below) were useful to monitor the spread of cooler water (shades of yellow) as the strong surface winds induced upwelling — especially since the resulting strong gradient in water temperatures was falsely interpreted as cloud by the GOES-16 Sea Surface Temperature product.

GOES-16 Shortwave Infrared (3.9 µm) images [click to play animation | MP4]

GOES-16 Shortwave Infrared (3.9 µm) images [click to play animation | MP4]

GOES-17 and GOES-16 Visible images (below) showed how the swath of Tehuano winds had spread out toward the south and southwest compared to the previous day.

GOES-17 (left) and GOES-16 (right) "Red" Visible (0.64 µm) images, with plots of surface wind barbs (speed in knots) [click to play animation | MP4]

GOES-17 (left) and GOES-16 (right) “Red” Visible (0.64 µm) images, with plots of surface wind barbs (speed in knots) [click to play animation | MP4]

In contrast to the previous day, the GOES-16 Dust Detection product (below) showed a larger coverage of dust on 06 March — with significantly more Medium Confidence areas.

GOES-16 "Red" Visible (0.64 µm) images + Dust Detection product [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images + Dust Detection product [click to play animation | MP4]

A Suomi NPP VIIRS True Color RGB image at 1930 UTC (below) showed the hazy corridor of Tehuano winds bracketed by rope clouds.

Suomi NPP VIIRS True Color RGB image [click to enlarge]

Suomi NPP VIIRS True Color RGB image [click to enlarge]

The Default location of GOES-17 Mesoscale Sector #2 has moved

March 5th, 2019 |

GOES-17 Mesoscale Domain Sector 2 at 1459 and 1500 UTC on 5 March 2019 (ABI Band 13, 10.3 µm, “Clean Window” imagery is shown) (Click to enlarge)

The planned change for Mesoscale Domain Sector #2, noted here, has occurred as scheduled on 5 March at 1500 UTC. The toggle above shows Mesoscale Domain Sector Two at 1459 and 1500 UTC on 5 March 2019.

The image below (courtesy Mat Gunshor, CIMSS) shows the default locations for all scanned sectors. The Full Disk is scanned every 5, 10 or 15 minutes (for Modes 4, 6 and 3, respectively; currently Mode 3 is the default). The PACUS (Pacific Ocean/US) domain, shown in the dashed line, is scanned every 5 minutes. The two Mesoscale sectors are scanned every minute in Modes 3 and 6; default locations are shown, one over the western United States (Mesoscale Domain Sector 1) and one over Alaska (Mesoscale Domain Sector 2), but these can be positioned anywhere over the Globe.

Default GOES-17 Scanning Sectors (Click to enlarge)