Dry air over Florida

February 14th, 2019 |

GOES-16 Low-level Water Vapor (7.3 µm) images, with and without a map overlay; rawinsonde sites are plotted in cyan [click to play animation | MP4]

GOES-16 Low-level Water Vapor (7.3 µm) images, with and without a map overlay; rawinsonde sites are plotted in cyan [click to play animation | MP4]

GOES-16 (GOES-East) Low-level Water Vapor (7.3 µm) images, with and without a map overlay (above), revealed that a portion of the western coastline of Florida around and north of Tampa (KTBW) could be seen on the Water Vapor imagery. Although more subtle, the St. Johns River south of Jacksonville (KJAX) and the northeast coast between Jacksonville and Cape Canaveral (KXMR) could also briefly be seen.

A plot of the sounding climatology for the Tampa site (source) showed that the Total Precipitable Water value of 0.18 inch at 12 UTC was just 0.02 inch higher than the record low value for all 14 February/12 UTC soundings (below).

Plot of mean and extreme Total Precipitable Water values for Tampa, Florida [click to enlarge]

Plot of mean and extreme Total Precipitable Water values for Tampa, Florida [click to enlarge]

The GOES-16 Total Precipitable Water product at 1207 UTC (below) showed the extent of the dry air that had moved across central Florida that morning.

GOES-16 Total Precipitable Water product at 1207 UTC [click to enlarge]

GOES-16 Total Precipitable Water product at 1207 UTC [click to enlarge]

Plots of GOES-16 Water Vapor weighting functions calculated using 00 UTC and 12 UTC rawinsonde data from Tampa, Florida (below) indicated that while the peak pressure of the 7.3 µm weighting function remained at 596.31 hPa during those 2 times, a significant radiation contribution was coming directly from the surface at 12 UTC. The presence of unusually dry air within the atmospheric column shifted all 3 water vapor band weighting functions to lower altitudes, thereby allowing a signature of the thermal contrast between land and water to be detected using 7.3 µm imagery.

Plots of GOES-16 Water Vapor weighting functions calculated from 00 UTC and 12 UTC rawinsonde data from Tampa, Florida [click to enlarge]

Plots of GOES-16 Water Vapor weighting functions calculated from 00 UTC and 12 UTC rawinsonde data from Tampa, Florida [click to enlarge]

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