Tehuano wind eventAfter 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.The GOES-16 Dust Detection product (below) did portray Low to Medium-Confidence areas of dust within the gap wind flow. 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). 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). A NOAA-20 VIIRS True Color Red-Green-Blue (RGB) image viewed using RealEarth (below) also showed the hazy signature of dust-laden air.
===== 06 March Update =====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 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-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. 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. A Suomi NPP VIIRS True Color RGB image at 1930 UTC (below) showed the hazy corridor of Tehuano winds bracketed by rope clouds.