Alert archive / New Jersey / Mesoscale Discussions in 2021
Mesoscale Discussion 1558
The Storm Prediction Center issued this mesoscale discussion at Aug 19, 2021, 12:44 AM EDT for 8 counties in New Jersey; Richmond County, New York; 4 counties in Pennsylvania. It was in force for 61 min.
The area
The outline as issued.
The facts
- Issued
- Aug 19, 2021, 12:44 AM EDT (04:44 UTC)
- Expired
- Aug 19, 2021, 1:45 AM EDT
- In force
- 61 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 5%
Counties Burlington County, NJ, Hudson County, NJ, Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Monmouth County, NJ, Somerset County, NJ, Union County, NJ, Richmond County, NY, Bucks County, PA, Delaware County, PA, Montgomery County, PA, Philadelphia County, PA
The radar
The Philadelphia radar (KDIX), 50 km from the middle of the area, began a volume at 04:48 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 00:00Z, 4.7 hours before the alert went out and 172 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
- 491 J/kg
- Mixed-layer CIN
- -11 J/kg
- Mixed-layer LCL
- 580 m above ground
- 0-6 km bulk shear
- 21 kt
- 0-1 km storm-relative helicity
- 62 m²/s²
- 0-3 km storm-relative helicity
- 103 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
896 ACUS11 KWNS 190444 SWOMCD SPC MCD 190444 NYZ000-NJZ000-PAZ000-190545- Mesoscale Discussion 1558 NWS Storm Prediction Center Norman OK 1144 PM CDT Wed Aug 18 2021 Areas affected...southeast PA...central NJ Concerning...Severe potential...Watch unlikely Valid 190444Z - 190545Z Probability of Watch Issuance...5 percent SUMMARY...A brief/weak tornado cannot be ruled out over the next several hours as a convective band moves east across central NJ. The low probability and magnitude of the threat will likely preclude a tornado watch issuance. Convective trends will continue to be monitored. DISCUSSION...Surface analysis placed the center of post-tropical-cyclone Fred near Williamsport, PA. Surface temperatures over NJ are in the upper 70s to near 80 deg F with mid 70s dewpoints. The hodograph indicated by the Fort Dix, NJ 88D VAD indicates only modest low-level shear. Nonetheless, a very moist boundary layer with 30-35 kt 1 km flow is yielding a conditional scenario for weak/transient rotation embedded in the convective band. As a result, a weak/brief tornado cannot be ruled out. ..Smith/Thompson.. 08/19/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...OKX...PHI... LAT...LON 40537528 40787410 40337389 39827444 39867557 40537528
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.