Alert archive / North Carolina / Mesoscale Discussions in 2020
Mesoscale Discussion 1821
The Storm Prediction Center issued this mesoscale discussion at Nov 30, 2020, 12:16 AM EST for Brunswick County, New Hanover County, North Carolina. It was in force for 119 min.
The area
The outline as issued.
The facts
- Issued
- Nov 30, 2020, 12:16 AM EST (05:16 UTC)
- Expired
- Nov 30, 2020, 2:15 AM EST
- In force
- 119 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 5%
Counties Brunswick County, NC, New Hanover County, NC
The radar
The Morehead City radar (KMHX), 80 km from the middle of the area, began a volume at 05:16 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
The nearest sounding before it
Newport, NC (KMHX), launched 00:00Z, 5.3 hours before the alert went out and 80 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 944 m above ground
- 0-6 km bulk shear
- 49 kt
- 0-1 km storm-relative helicity
- 162 m²/s²
- 0-3 km storm-relative helicity
- 189 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
115
ACUS11 KWNS 300517
SWOMCD
SPC MCD 300516
NCZ000-300715-
Mesoscale Discussion 1821
NWS Storm Prediction Center Norman OK
1116 PM CST Sun Nov 29 2020
Areas affected...The Southern North Carolina Coast
Concerning...Severe potential...Watch unlikely
Valid 300516Z - 300715Z
Probability of Watch Issuance...5 percent
SUMMARY...Strong convection may gradually move onshore over the next
few hours and pose the risk for isolated strong to severe winds and
perhaps a brief tornado.
DISCUSSION...Recent radar imagery from the southern NC coast shows a
few stronger convective cells offshore that have exhibited
supercellular characteristics over the past hour. Northward moisture
flux into the region (as sampled by the 00 UTC CHS sounding) has
allowed for an increase in instability with offshore MLCAPE values
estimated to be between 500-1000 J/kg per recent RAP Mesoanalysis.
This instability, coupled with strong (50 knot) deep layer shear
over the region has allow for a few stronger storms to persist as
they migrate north/northeastward. A few of these storms may move
onshore and introduce a severe wind threat to the immediate coastal
areas. The LTX VWP recently sampled 240 m2/s2 0-1 km SRH, which
suggests that sufficiently low-level shear is in place along the
coast to support at least a low-end tornado threat with any storm
exhibiting a sustained mesocyclone. No watch is currently
anticipated since this threat appears to be limited spatially to
just the coastal areas. However, a more favorable environment should
continue to progress inland overnight as the main surface low
(currently over eastern AL/western GA) deepens as it translates
northeast through morning.
..Moore/Grams.. 11/30/2020
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MHX...ILM...
LAT...LON 33807844 34207821 34467777 34687731 34857688 34827652
34627613 34407613 34197640 33977707 33737768 33587808
33627833 33807844SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Nov 30, 12:26 PM EST | Mesoscale Discussion | SPC | Beaufort, Bertie, Camden, Carteret, Chowan, Craven and 23 more | 3 hr |
Nearby
Mesoscale Discussions in North Carolina, 2020Every mesoscale discussion in 2020
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.