Orphan anvil over the Atlantic Ocean

October 3rd, 2019 |


The interesting east-to-west moving cold (brighter white) infrared signature mentioned above was determined by another Twitter user to be the convective debris of an isolated orphan anvil that developed over the Atlantic Ocean east of Florida (and north of the Bahamas) toward sunset on 03 October 2019. A comparison of GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images is shown below.

GOES-16 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.35 µm, bottom) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.35 µm, bottom) images [click to play animation | MP4]

The convective tower producing the orphan anvil was still dimly illuminated by the setting sun at 2301 UTC (below), when cloud-top infrared brightness temperatures first became colder than -25ºC (darker blue pixel).

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images at 2301 UTC [click to enlarge]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images at 2301 UTC [click to enlarge]

The coldest infrared brightness temperature exhibited by the orphan anvil was -29ºC at 2316 UTC — which closely corresponded to the 313 hPa pressure level in rawinsonde data from Cocoa Beach, Florida at 00 UTC (below). Wind speeds at that altitude were 42 knots; the 300 hPa analysis at 00 UTC showed a 50-knot wind speed maxima approaching the orphan anvil region from the northeast.

Plot of 00 UTC rawinsonde data from Cocoa Beach, Florida [click to enlarge]

Plot of 00 UTC rawinsonde data from Cocoa Beach, Florida [click to enlarge]

The orphan anvil signature was only apparent in Infrared imagery until about 2336 UTC — but since the surrounding atmosphere was fairly dry, the westward transport of moist convective debris could be tracked for another 3 hours using GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor imagery (below).

GOES-16 Low-level (7.3 µm, bottom), Mid-level (6.9 µm, middle) and Upper-level (6.2 µm, top) Water Vapor images [click to play animation | MP4]

GOES-16 Low-level (7.3 µm, bottom), Mid-level (6.9 µm, middle) and Upper-level (6.2 µm, top) Water Vapor images [click to play animation | MP4]

Orphan anvils often appear shortly before the onset of significant convective development — signalling that convective inhibition is weakening — as previously  discussed here, here, here, here and here.

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