Orphan anvil over the Atlantic Ocean
Something very strange off the Florida east coast… honestly not sure what that is pic.twitter.com/QjvN9YsWeU
— Brian Cizek (@CycloneCizekWx) October 4, 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. 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). 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. 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). 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.