Alert archive / New York / Mesoscale Discussions in 2021
Mesoscale Discussion 1679
The Storm Prediction Center issued this mesoscale discussion at Sep 1, 2021, 11:20 PM EDT for 5 counties in Massachusetts; 7 counties in New York; 4 counties in Rhode Island. It was in force for 85 min.
The area
The outline as issued.
The facts
- Issued
- Sep 1, 2021, 11:20 PM EDT (03:20 UTC)
- Expired
- Sep 2, 2021, 12:45 AM EDT
- In force
- 85 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 484
Counties Barnstable County, MA, Bristol County, MA, Dukes County, MA, Nantucket County, MA, Plymouth County, MA, Bronx County, NY, Kings County, NY, Nassau County, NY, New York County, NY, Queens County, NY, Suffolk County, NY, Westchester County, NY, Bristol County, RI, Kent County, RI, Newport County, RI, Washington County, RI
The radar
The Brookhaven radar (KOKX), 59 km from the middle of the area, began a volume at 03:24 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
Brookhaven, NY (KOKX), launched 00:00Z, 3.3 hours before the alert went out and 59 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
- 123 J/kg
- Mixed-layer CIN
- -47 J/kg
- Mixed-layer LCL
- 512 m above ground
- 0-6 km bulk shear
- 53 kt
- 0-1 km storm-relative helicity
- 279 m²/s²
- 0-3 km storm-relative helicity
- 456 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 1.2
The text
As transmitted.
783
ACUS11 KWNS 020320
SWOMCD
SPC MCD 020320
MAZ000-RIZ000-CTZ000-NYZ000-NJZ000-020445-
Mesoscale Discussion 1679
NWS Storm Prediction Center Norman OK
1020 PM CDT Wed Sep 01 2021
Areas affected...far northern New Jersey...southern New York...Long
Island...and far southern New England
Concerning...Tornado Watch 484...
Valid 020320Z - 020445Z
The severe weather threat for Tornado Watch 484 continues.
SUMMARY...Thunderstorms currently moving across Long Island and
southern New England will continue to pose a risk of strong
thunderstorm winds and a couple of tornadoes. A new watch downstream
of Tornado Watch #484 will be issued.
DISCUSSION...The remnant low-level circulation of post-tropical
cyclone Ida continues to move northeast toward the greater New York
City area. The low-level wind field continues to advect a very warm,
moist air northward into southern New England as a warm front slowly
lifts north across Long Island. Time-evolution VAD winds from Upton,
NY, (KOKX) suggests that the warm front is very near or just north
of the radar. Additionally, the time evolution of KOKX's VAD winds
indicates a strengthening wind field that veers with height, leading
to 0-1 kilometer SRH in excess of 800 m2/s2.
As thunderstorms continue to move east from northern New
Jersey/southern New York, across Long Island and southern New
England, they will interact with this extremely favorable kinematic
environment. The result is a continued potential for a couple of
tornadoes and strong thunderstorm winds along and south of the warm
front. The most appreciable tornado risk will be in the vicinity of
this lifting warm front, but how far north it lifts before being
overtaken by the approaching thunderstorms is uncertain. Portions o
coastal and near-coastal areas downstream from Tornado Watch #484
across southern New England will need a new tornado watch.
..Marsh.. 09/02/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BOX...OKX...ALY...
LAT...LON 41317391 42217009 41846950 41126950 40277345 40407386
40837405 41317391SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 1, 11:37 PM EDT | Tornado Watch | SPC | Barnstable, Bristol, Dukes, Nantucket, Plymouth | 7 hr |
| Sep 2, 3:38 AM EDT | Mesoscale Discussion | SPC | Barnstable, Dukes, Nantucket | 97 min |
| Sep 1, 8:32 PM EDT | Mesoscale Discussion | SPC | Bronx, Kings, Nassau, New York, Queens, Richmond and 1 more | 88 min |
Nearby
Mesoscale Discussions in New York, 2021Mesoscale Discussions in Connecticut, 2021Mesoscale Discussions in Massachusetts, 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.