Case Description: 5 December 2018

Summary

Three cells initiate and grow near the AMF into small sizes

Description

Convection early during the day clears out of the region by 10 UTC and convective initiations start by 17 UTC. By 19:45 UTC, three cells develop and grow to the north of the AMF and one to the southwest behind the ridgeline (not observable by the CSAPR2). CAPE values are in the lower third of their ranges (at 18 UTC MUCAPE=823; MLCAPE=519 J kg^-1).

Available assets

CSAPR2, G1 flight, GOES rapid scan, RELAMPAGO mission (35 soundings), CSU C-Band data

Critical period: 17:00–20:00

00 System initiates over AMF and grows
45 Second system initiates north of the AMF and grows
45 Third system initiates north of the AMF and grows
45 Fourth system initiates to the SW of the AMF behind the ridgeline

Brightness temperature, 2018-12-05 19:45 UTC — Figure 5 GOES16 band 13 brightness temperature at 2018-12-05 at 19:45 UTC. Three systems initiate northeast of the AMF and one to the southwest.

Available LES ensemble members

Table 5 Summary of LES cloud behavior for 2018-12-05
Impression	Ensemble Member	Cloud Behavior
Bust	EDA05-Morr	Really overdoes it.
Bust	ERA5-Morr	At observed convective initiation, the simulation already has a ver large convective system over the AMF.
Dud	GEFS01	Initiates to northwest on ridge versus observations and 0.5 h late. Systems are seriously underdeveloped.
Dud	GEFS01-Smag	SGS sensitivity test with Smagorinksy using default parameters. Similar behavior to GEFS01.
Dud	GEFS01-SmagCs	SGS sensitivity test with Smagorinsky and modified Cs parameter. Similar behavior to GEFS01.
Dud	GEFS01-TKECk	SGS sensitivity test with TKE an modified Ck parameter. Similar behavior to GEFS01.
Poor	GEFS01-Morr	Initiates northwest 0.5 h late. Development is blobular versus observation’s line and misses norther cell. By 19 UTC, looks similar to observations, though lacks the northeast cell at perimeter.
Bad	GEFS02-Morr	Scattered convection before observed convective onset, which then broaden further. The ‘hits’ for skill scoring tend to arise from broad convection that happened to overlap the observations despite the simulated structure being very different from what occurred.