Alert archive / New Jersey / Mesoscale Discussions in 2021
Mesoscale Discussion 1490
The Storm Prediction Center issued this mesoscale discussion at Aug 11, 2021, 6:44 PM EDT for 5 states. It was in force for 91 min.
The area
The outline as issued.
The facts
- Issued
- Aug 11, 2021, 6:44 PM EDT (22:44 UTC)
- Expired
- Aug 11, 2021, 8:15 PM EDT
- In force
- 91 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 427
All 43 counties
New Castle County, DE, Cecil County, MD, Atlantic County, NJ, Bergen County, NJ, Burlington County, NJ, Camden County, NJ, Cumberland County, NJ, Essex County, NJ, Gloucester County, NJ, Hudson County, NJ, Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Monmouth County, NJ, Morris County, NJ, Ocean County, NJ, Passaic County, NJ, Salem County, NJ, Somerset County, NJ, Sussex County, NJ, Union County, NJ, Warren County, NJ, Bronx County, NY, Kings County, NY, New York County, NY, Orange County, NY, Putnam County, NY, Queens County, NY, Richmond County, NY, Rockland County, NY, Westchester County, NY, Berks County, PA, Bucks County, PA, Carbon County, PA, Chester County, PA, Delaware County, PA, Lancaster County, PA, Lehigh County, PA, Monroe County, PA, Montgomery County, PA, Northampton County, PA, Philadelphia County, PA, Pike County, PA
The radar
The Philadelphia radar (KDIX), 67 km from the middle of the area, began a volume at 22:47 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
Brookhaven, NY (KOKX), launched 12:00Z, 10.7 hours before the alert went out and 178 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
- 977 J/kg
- Mixed-layer CIN
- -44 J/kg
- Mixed-layer LCL
- 711 m above ground
- 0-6 km bulk shear
- 15 kt
- 0-1 km storm-relative helicity
- 29 m²/s²
- 0-3 km storm-relative helicity
- 18 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
300
ACUS11 KWNS 112245
SWOMCD
SPC MCD 112244
CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-120015-
Mesoscale Discussion 1490
NWS Storm Prediction Center Norman OK
0544 PM CDT Wed Aug 11 2021
Areas affected...Eastern PA into Southern NY...NJ...MD...and DE
Concerning...Severe Thunderstorm Watch 427...
Valid 112244Z - 120015Z
The severe weather threat for Severe Thunderstorm Watch 427
continues.
SUMMARY...Strong to severe storms capable of damaging winds
continue. A local extension of WW427 maybe required across portions
of NJ and DE this evening.
DISCUSSION...A cluster of thunderstorms with a history of wind
damage across southern PA will continue to pose a risk for damaging
wind gusts this evening. Ongoing within an unstable (2000-3000 J/kg
of MLCAPE) but weakly sheared environment (<20 kts of effective
shear), convection has remained marginally organized in several
bands of multicell storms. Recent radar trends show additional
convective development ahead of the main band across northwestern NJ
suggesting storms will likely continue to the Atlantic coast. With
strong instability in place robust updrafts capable of strong
outflow winds appear likely. A local watch extension across NJ may
be required as storms approach the eastern edge of WW427 in the next
hour or two.
Farther north across southern NY, isolated severe storms have
continued with a few instances of damaging wind gusts over the last
couple of hours. Storms have generally shown less organization
casting uncertainty on the severe threat for the remainder of the
evening. As such, a few severe storms will remain possible but
coverage is expected to remain low enough that a watch is unlikely.
..Lyons/Goss.. 08/11/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OKX...ALY...PHI...BGM...CTP...LWX...
LAT...LON 40747603 41477497 41687421 41597358 41457347 41227353
40847378 40057400 39597418 39347456 39257501 39417577
39557621 39757646 40167648 40747603SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 11, 3:02 PM EDT | Severe Thunderstorm Watch | SPC | Kent, New Castle | 6 hr |
| Aug 11, 1:01 PM EDT | Mesoscale Discussion | SPC | Carroll, Charles, Frederick, Howard, Montgomery, Prince George's and 1 more | 89 min |
| Aug 11, 2:02 PM EDT | Severe Thunderstorm Watch | SPC | Allegany, Anne Arundel, Baltimore, Calvert, Carroll, Cecil and 9 more | 6 hr |
| Aug 11, 3:47 PM EDT | Mesoscale Discussion | SPC | Anne Arundel, Baltimore, Calvert, Carroll, Cecil, Charles and 9 more | 88 min |
| Aug 11, 4:57 PM EDT | Mesoscale Discussion | SPC | Albany, Columbia, Dutchess, Essex, Greene, Orange and 7 more | 93 min |
| Aug 11, 9:31 AM EDT | Mesoscale Discussion | SPC | Lawrence, Mercer | 89 min |
| Aug 11, 11:50 AM EDT | Mesoscale Discussion | SPC | Allegheny, Armstrong, Beaver, Butler, Cambria, Clarion and 12 more | 115 min |
| Aug 11, 2:03 PM EDT | Mesoscale Discussion | SPC | Adams, Armstrong, Bedford, Berks, Blair, Bucks and 42 more | 87 min |
| Aug 11, 4:57 PM EDT | Severe Thunderstorm Watch | SPC | Crawford, Erie, Lawrence, Mercer, Venango | 3 hr |
Nearby
Mesoscale Discussions in New Jersey, 2021Mesoscale Discussions in Pennsylvania, 2021Mesoscale Discussions in New York, 2021Every mesoscale discussion in 2021
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.