Alert archive / New Jersey / Mesoscale Discussions in 2021
Mesoscale Discussion 1671
The Storm Prediction Center issued this mesoscale discussion at Sep 1, 2021, 3:09 PM EDT for 4 states. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 1, 2021, 3:09 PM EDT (19:09 UTC)
- Expired
- Sep 1, 2021, 5:45 PM EDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 482...483
All 27 counties
Kent County, DE, New Castle County, DE, Sussex County, DE, Caroline County, MD, Cecil County, MD, Dorchester County, MD, Harford County, MD, Kent County, MD, Queen Anne's County, MD, Talbot County, MD, Wicomico County, MD, Atlantic County, NJ, Burlington County, NJ, Camden County, NJ, Cape May County, NJ, Cumberland County, NJ, Gloucester County, NJ, Mercer County, NJ, Middlesex County, NJ, Monmouth County, NJ, Ocean County, NJ, Salem County, NJ, Bucks County, PA, Chester County, PA, Delaware County, PA, Montgomery County, PA, Philadelphia County, PA
The radar
The Dover AFB radar (KDOX), 61 km from the middle of the area, began a volume at 19:09 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 watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Wallops Is Stn, VA (KWAL), launched 12:00Z, 7.2 hours before the alert went out and 160 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
- 515 J/kg
- Mixed-layer CIN
- -76 J/kg
- Mixed-layer LCL
- 955 m above ground
- 0-6 km bulk shear
- 29 kt
- 0-1 km storm-relative helicity
- 57 m²/s²
- 0-3 km storm-relative helicity
- 89 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 1.3
The text
As transmitted.
468
ACUS11 KWNS 011910
SWOMCD
SPC MCD 011909
NJZ000-NYZ000-PAZ000-DEZ000-MDZ000-012145-
Mesoscale Discussion 1671
NWS Storm Prediction Center Norman OK
0209 PM CDT Wed Sep 01 2021
Areas affected...eastern Maryland...Delaware...southern New
Jersey...far southeast Pennsylvania
Concerning...Tornado Watch 482...483...
Valid 011909Z - 012145Z
The severe weather threat for Tornado Watch 482, 483 continues.
SUMMARY...A threat for a few tornadoes along with damaging wind
gusts will shift northeast out of Maryland and into Delaware,
southern New Jersey, and extreme southeast Pennsylvania.
DISCUSSION...Surface analysis shows a stationary front across
northern MD, southeast PA and into southern NJ, with a very moist
air mass to the south. Given persistent southerly surface winds
impinging on this front, it is likely that sufficient elevated
instability exists immediately north of the boundary to support
severe storms, most likely in the form of an MCS which should travel
east/northeastward. Damaging winds will be possible with such
activity, with embedded circulations possible.
Otherwise, a tornado threat remains on and south of the front, where
storms will have access to around 2000 J/kg SBCAPE. The tornado risk
is maximized for northeastward-moving cells, providing maximum SRH
per 16Z IAD sounding. Other cells moving north/northwestward ahead
of the consolidating convective line may still yield strong gusts.
..Jewell.. 09/01/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OKX...PHI...AKQ...CTP...LWX...
LAT...LON 38877476 38197573 38147598 38257641 38677655 39097656
39487656 39687656 39927640 40167577 40487485 40587427
40307390 39837404 39427426 38877476SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 1, 4:01 AM EDT | Mesoscale Discussion | SPC | New Castle | 119 min |
| Sep 1, 11:03 AM EDT | Mesoscale Discussion | SPC | Kent, New Castle, Sussex | 2 hr |
| Sep 1, 12:40 PM EDT | Tornado Watch | SPC | Kent, New Castle, Sussex | 9 hr |
| Sep 1, 4:28 PM EDT | Mesoscale Discussion | SPC | New Castle | 2 hr |
| Sep 1, 12:19 AM EDT | Mesoscale Discussion | SPC | Anne Arundel, Calvert, Charles, Montgomery, Prince George's | 86 min |
| Sep 1, 12:56 AM EDT | Tornado Watch | SPC | Anne Arundel, Baltimore, Carroll, Charles, Frederick, Harford and 4 more | 6 hr |
| Sep 1, 11:46 AM EDT | Tornado Watch | SPC | Anne Arundel, Baltimore, Calvert, Carroll, Cecil, Charles and 11 more | 9 hr |
| Sep 1, 1:32 PM EDT | Mesoscale Discussion | SPC | Anne Arundel, Baltimore, Calvert, Carroll, Cecil, Charles and 9 more | 118 min |
| Sep 1, 6:22 PM EDT | Tornado Watch | SPC | Bergen, Essex, Hudson, Passaic, Union | 7 hr |
| Sep 1, 6:34 PM EDT | Mesoscale Discussion | SPC | Burlington, Camden, Gloucester, Hudson, Mercer, Middlesex and 3 more | 56 min |
Nearby
Mesoscale Discussions in New Jersey, 2021Mesoscale Discussions in Maryland, 2021Mesoscale Discussions in Pennsylvania, 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.