An Evaluation of the Diagnostic and Prognostic
Implications of Orphan Anvils (85)
Chauncy Schultz, NOAA/NWS,
Bismarck, ND
Ariel Cohen, NOAA/NWS
Abstract:
The arrival of the GOES-R
series of satellites has provided forecasters with a wealth of high spatial and
temporal resolution imagery from which they are able to visualize the process
of convective initiation with much more detail than ever before. One of the
more interesting and relevant diagnostic features regularly observed by the
GOES-R series of satellites is the orphan anvil, which is the remnant cirrus
from failed updraft attempts. Such orphan anvils can indicate that a capping
inversion is weakening and that subsequent attempts at convective initiation
may be successful (Line et al. 2016). However, detailed analysis of prolonged
attempts at convective initiation and associated extensive orphan anvil
generation along a weak surface dryline in North Dakota on 21 July 2017
suggests that orphan anvils can also be indicative of the detrimental effects
of dry air entrainment or parcel detrainment on robust updraft development. In
this case, a tornadic supercell developed only once the significant orphan
anvils spread downwind away from the dryline and into an air mass characterized
by higher moisture content above the lifted condensation level. This
presentation will illustrate this evolution, compare and contrast it with more
transient orphan anvils and their associated environments, and discuss
prognostic implications that forecasters should consider when orphan anvils are
being generated, including their capability to provide evidence of the strength
of high-level storm-relative flow, as they did in the 21 July 2017 case.