Gravity waves over the Gulf of Mexico and Florida

January 22nd, 2020 |

GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images, with pilot reports of turbulence [click to play animation | MP4]

GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images, with pilot reports of turbulence [click to play animation | MP4]

GOES-16 (GOES-East) Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above) showed a packet of gravity waves over the eastern Gulf of Mexico and southern Florida on 22 January 2020. Later time in the time period, there were isolated pilot reports of moderate turbulence in the vicinity of the waves (though it’s uncertain whether the gravity waves were directly responsible).

What caused these gravity waves to form and slowly propagate southeastward is also uncertain — earning this example its place in the “What the heck is this?” blog category. The SPC Mesoscale Analysis at 07 UTC (below) did show weak convergence of 300 hPa ageostrophic winds (dark blue oval) in the entrance region of a secondary jet streak “J” over the Gulf of Mexico — this convergence could have played a role in the gravity wave development.

SPC Mesoscale Analysis valid at 07 UTC, showing 300 hPa height, isotachs and ageostrophic winds [click to enlarge]

SPC Mesoscale Analysis valid at 07 UTC, showing 300 hPa height, isotachs and ageostrophic winds [click to enlarge]

GOES-16 Derived Motion Winds (calculated using 6.9 µm imagery) in the vicinity of the gravity waves (below) had velocities in the 50-60 knot range at pressure levels of 370-380 hPa (0916 UTC).

GOES-16 Water Vapor (6.2 um) Derived Motion Winds [click to enlarge]

GOES-16 Water Vapor (6.9 µm) Derived Motion Winds [click to enlarge]

Also of note was the fact that the surface of southern Florida was sensed by GOES-16 Low-level Water Vapor imagery (below).

GOES-16 Low-level (7.3 µm) Water Vapor images, with pilot reports of turbulence [click to play animation | MP4]

GOES-16 Low-level (7.3 µm) Water Vapor images, with pilot reports of turbulence [click to play animation | MP4]

With an unseasonably cold, dry air mass moving southward over the peninsula, the 7.3 µm water vapor weighting functions were shifted to lower altitudes at Miami and Key West (below) — this allowed the thermal contrast between relatively cool land surfaces and the surrounding warmer water to be seen in the 7.3 µm imagery.

GOES-16 weighting functions for the 7.3 µm (violet), 6.9 µm (blue) and 6.2 µm (green) Water Vapor spectral bands, calculated using 12 UTC rawinsonde data from Miami, Florida [click to enlarge]

GOES-16 weighting functions for the 7.3 µm (violet), 6.9 µm (blue) and 6.2 µm (green) Water Vapor spectral bands, calculated using 12 UTC rawinsonde data from Miami, Florida [click to enlarge]

GOES-16 weighting functions for the 7.3 µm (violet), 6.9 µm (blue) and 6.2 µm (green) Water Vapor spectral bands [click to enlarge]

GOES-16 weighting functions for the 7.3 µm (violet), 6.9 µm (blue) and 6.2 µm (green) Water Vapor spectral bands, calculated using 12 UTC rawinsonde data from Key West, Florida [click to enlarge]

In fact, at Key West the Total Precipitable Water value of 0.3 inch calculated from 12 UTC rawinsonde data (below) was a new record for the date/time (the previous record minimum value was 0.36 inch).

Climatology of Total Precipitable Water for the Key West, Florida rawinsonde site [click to enlarge]

Climatology of Total Precipitable Water for the Key West, Florida rawinsonde site [click to enlarge]