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]

Southern US storm, and a Tehuano wind event

December 15th, 2018 |

GOES-16 Low-level Water Vapor (7.3 µm) images, 13-15 December [click to play MP4 animation]

GOES-16 Low-level Water Vapor (7.3 µm) images, 13-15 December [click to play MP4 animation]

A large midlatitude cyclone moved from the southern High Plains to the Lower Mississippi Valley during the 13 December15 December 2018 period (surface analyses) — GOES-16 (GOES-East) Low-level Water Vapor (7.3 µm) images (above) showed the evolution of this system.

The corresponding GOES-16 Water Vapor images with plots of hourly surface wind gusts are shown below; peak wind gusts exceeding 50 knots occurred in parts of Colorado, New Mexico and Texas on 13 December.

GOES-16 Low-level Water Vapor (7.3 µm) images with hourly plots of surface wind gusts, 13-15 December [click to play MP4 animation]

GOES-16 Low-level Water Vapor (7.3 µm) images with hourly plots of surface wind gusts in knots, 13-15 December [click to play MP4 animation]

This event was unusually windy in South Texas and the Rio Grande Valley:

Another notable aspect of this storm was a very localized area of heavy snowfall just south of Sweetwater, Texas:


The remnant patch of snow cover was evident in VIIRS Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) imagery on 14 and 15 December (below). The heaviest snowfall occurred over an isolated ridge along the eastern edge of the Edwards Plateau, where elevations of 2500-2600 feet were about 500 feet higher than the adjacent rolling plains. Since snow is a very effective absorber of energy at the 1.61 µm wavelength, it appeared dark on the Snow/Ice imagery.

Topography, Suomi NPP VIIRS Visible (0.64 µm) and Near-Infrared "Snow/Ice" (1.61 µm) images on 14 December [click to enlarge]

Topography plus Suomi NPP VIIRS Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images on 14 December [click to enlarge]

Topography plus NOAA-20 VIIRS Visible (0.64 µm) and Near-Infrared "Snow/Ice" (1.61 µm) images on 15 December [click to enlarge]

Topography plus NOAA-20 VIIRS Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images on 15 December [click to enlarge]

The residual snow cover on 14 December was also seen in Terra/Aqua MODIS True Color and False Color Red-Green-Blue (RGB) images, viewed using RealEarth (below). The snow appeared as shades of cyan in the False Color images.

Terra/Aqua MODIS True Color and False Color images on 14 December [click to enlarge]

Terra/Aqua MODIS True Color and False Color images on 14 December [click to enlarge]

A toggle between Terra MODIS True Color RGB images on the late morning of 14 and 15 December (below) demonstrated the amount of snow melt in 24 hours.

Terra MODIS True Color RGB images on 14 and 15 December [click to enlarge]

Terra MODIS True Color RGB images on 14 and 15 December [click to enlarge]

The strong cold front associated with this storm moved rapidly southward across the western Gulf of Mexico on 14 December (surface analyses), crossing the terrain of the Isthmus of Tehuantepec in southern Mexico and emerging into the Gulf of Tehuantepec as a gap wind (known as a Tehuano wind). A curved rope cloud marking the leading edge of the Tehuano winds was evident on GOES-17 and GOES-16 “Red” Visible (0.64 µm) images (below).

* GOES-17 images shown here are preliminary and non-operational *

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

GOES-17 (left) and GOES-16 (right) “Red” Visible (0.64 µm) images [click to play animation | MP4]

A comparison of GOES-16 Visible imagery from 14 and 15 December (below) showed how far southwestward the gap winds spread out across the Pacific Ocean during those 2 days. Note that on 15 December there were ship reports with wind speeds of 50 knots, at 12 UTC and at 17 UTC.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images with surface and ship reports, 14-15 December [click to play animation | MP4]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images on 14 and 15 December (below) also showed the progression of the Tehuano wind rope cloud — the hazy signature of dust-laden air within the offshore flow was also apparent on the daytime True Color images.

NOAA-20 VIIRS True Color and Infrared Window (11.45 µm) images on 14 and 15 December [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images on 14 and 15 December [click to enlarge]

Metop-A and Metop-B ASCAT surface scatterometer winds across the western Gulf of Mexico [click to enlarge]

Metop-A and Metop-B ASCAT surface scatterometer winds across the western Gulf of Mexico [click to enlarge]

On 14 December, a sequence of EUMETSAT Metop-A and Metop-B ASCAT surface scatterometer winds (source) showed the cold front moving southward across the western Gulf of Mexico (above), and also showed the northerly gap wind flow just beginning to emerge into the Gulf of Tehuantepec around 1607 UTC (below).

Metop-A and Metop-B ASCAT surface scatterometer winds across the southern Gulf of Mexico and the Gulf of Tehuantepec [click to enlarge]

Metop-A and Metop-B ASCAT surface scatterometer winds across the far southern Gulf of Mexico and the Gulf of Tehuantepec [click to enlarge]

The plume of dry air being transported southwestward across the Pacific Ocean by the gap winds was apparent on MIMIC Total Precipitable Water images (below). The majority of this dry air was within the surface-850 hPa layer (21 UTC comparison).

MIMIC Total Precipitable Water product (Total column, and Surface-850 hPa layer) [click to play animation]

MIMIC Total Precipitable Water product (Total column, and Surface-850 hPa layer) [click to play animation]

Tehuano wind event

April 8th, 2014 |
GOES-13 0.63 µm visible channel images (click to play animation)

GOES-13 0.63 µm visible channel images (click to play animation)

As we have seen a number of times during the Winter 2013/2014 season, another strong Tehuano wind event occurred on 08 April 2014. McIDAS images of GOES-13 0.63 µm visible channel data (above; click image to play animation) showed distinct arc clouds marking the leading edge of 2 pulses of gap winds emerging southward over the Gulf of Tehuantepec. The second (later) pulse of gap winds appeared to be stronger, and transported plumes of blowing dust to the south.

A timely overpass of a Metop polar-orbiting satellite provided ASCAT surface scaterometer winds which showed the fanning out of the Tehuano flow at 16:20 UTC (below). An advisory for the development of Storm Force winds had been issued by the NOAA Ocean Prediction Center for the Gulf of Tehuantepec.

GOES-13 10.7 µm IR image with Metop ASCAT surface scatterometer winds

GOES-13 10.7 µm IR image with Metop ASCAT surface scatterometer winds

MADIS 1-hour interval satellite winds (below; click image to play animation) tracked the velocity of the arc cloud and dust plumes during the day, which were moving at speeds up to 30 knots.

GOES-13 10.7 µm IR images with MADIS 1-hour satellite winds (click to play animation)

GOES-13 10.7 µm IR images with MADIS 1-hour satellite winds (click to play animation)

Past cases of well-defined Tehuano wind events can be found here.

Tehuano wind event in the wake of a strong eastern US winter storm

January 3rd, 2014 |
SSEC RealEarth 24-hour snowfall total map

SSEC RealEarth 24-hour snowfall total map

A strong winter storm affected much of the central and eastern US during the 02 January03 January 2014 period. A map of SSEC RealEarth 24-hour snowfall totals (above) shows how widespread the resulting snowfall was, with amounts as high as 24 inches in Massachusetts abd 22 inches in New York (WPC storm summary).

As the storm system departed over the Atlantic Ocean on 03 January, an AWIPS image comparison of the 17:53 UTC (12:53 PM Eastern time) Suomi NPP VIIRS 0.64 µm visible channel data and the corresponding false-color “snow vs cloud discrimination” Red/Green/Blue (RGB) product (below) showed the areal coverage of snow on the ground (varying shades of red on the RGB image). Some patches of supercooled water droplet clouds (varying shades of white on the RGB image) could be seen streaming off of Lake Erie and Lake Ontario; in fact, a closer look revealed mesoscale bands of “lake-effect snow” downwind of the Finger Lakes in western New York, and also downwind of Lake Champlain along the New York/Vermont border.

Suomi NPP VIIRS 0.64 µm visible channel image and False-color RGB image

Suomi NPP VIIRS 0.64 µm visible channel image and False-color RGB image

Cold air moving southward in the wake of the storm crossed the western Gulf of Mexico, moved through the Chivela mountain pass in southern Mexico, and eventually emerged over the Pacific Ocean in the Gulf of Tehuantepec — this type of mountain gap wind flow is known as a Tehuano wind event or a “Tehuantepecer”. An image of Metop ASCAT surface scatterometer winds at 02:36 UTC (below) showed that a large area of northerly gale force winds (red wind barbs) was present over the Gulf of Tehuantepec, with maximum remotely-sensed wind speeds of 41 knots. The tropical surface analysis (cyan) displayed the fractured cold frontal boundary that had advanced into southern Mexico; behind the cold front along the Gulf of Mexico coast at Veracruz (station identifier MMVR), the surface visibility at the time was reduced to 6 miles due to blowing sand (time series of MMVR surface reports). Surface reports at Ixtepec (station identifier MMIT) along the Gulf of Tehuantepec were sparse, but did show northerly winds gusting to 37 knots at 17 UTC (time series of MMIT surface reports).

GOES-13 10.7 µm IR image, with Metop ASCAT surface scatterometer winds

GOES-13 10.7 µm IR image, with Metop ASCAT surface scatterometer winds

Daytime images of GOES-13 0.63 µm visible channel data on 03 January (below; click image to play animation) showed the hazy plume of blowing dust and sand moving southwestward, with the boundaries of the strong Tehauno winds marked by long, narrow rope clouds.

GOES-13 0.63 µm visible channel images (click to play animation)

GOES-13 0.63 µm visible channel images (click to play animation)

A signature of the dry air (darker blue color enhancement) associated with the Tehuano winds could be seen on the MIMIC Total Precipitable Water product (below).

MIMIC Total Precipitable Water product, with tropical surface analyses

MIMIC Total Precipitable Water product, with tropical surface analyses