Alert archive / New York / Mesoscale Discussions in 2021
Mesoscale Discussion 1677
The Storm Prediction Center issued this mesoscale discussion at Sep 1, 2021, 8:32 PM EDT for 6 counties in New Jersey; 7 counties in New York. It was in force for 88 min.
The area
The outline as issued.
The facts
- Issued
- Sep 1, 2021, 8:32 PM EDT (00:32 UTC)
- Expired
- Sep 1, 2021, 10:00 PM EDT
- In force
- 88 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 484
Counties Essex County, NJ, Hudson County, NJ, Middlesex County, NJ, Monmouth County, NJ, Somerset County, NJ, Union County, NJ, Bronx County, NY, Kings County, NY, Nassau County, NY, New York County, NY, Queens County, NY, Richmond County, NY, Suffolk County, NY
The radar
The Brookhaven radar (KOKX), 67 km from the middle of the area, began a volume at 00:34 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, 0.5 hours before the alert went out and 67 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.
635
ACUS11 KWNS 020033
SWOMCD
SPC MCD 020032
NYZ000-CTZ000-NJZ000-020200-
Mesoscale Discussion 1677
NWS Storm Prediction Center Norman OK
0732 PM CDT Wed Sep 01 2021
Areas affected...Northern New Jersey...far southern New York and
Long Island
Concerning...Tornado Watch 484...
Valid 020032Z - 020200Z
The severe weather threat for Tornado Watch 484 continues.
SUMMARY...The tornado threat across far southern New York and Long
Island will increase as the warm sector moves northward in the next
couple of hours. Storm mode may moderate the the tornado threat, but
discrete/embedded supercells remain possible and would pose the
greatest risk.
DISCUSSION...Convection across far eastern Pennsylvania and central
New Jersey has generally congealed. While the potential for
tornadoes remains due to the low-level shear environment, the storm
mode suggests that tornadoes would generally be brief.
Some backing of surface winds is evident in surface observations in
eastern Long Island. Over the next couple of hours, this trend
should continue as low-level warm advection increases. Portions of
far southern New York and Long Island should eventually end up in
the warm sector. Improved thermodynamics will lead to a slightly
higher tornado potential, though this will continue to be modulated
by linear/cluster storm mode. KDIX radar imagery does show a couple
of more discrete storms moving northeast out of central New Jersey.
These storms, and other discrete storms that can develop, would pose
a greater tornado threat.
..Wendt.. 09/02/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OKX...PHI...
LAT...LON 40547466 40937416 41127297 41207210 40977168 40447273
40207411 40147439 40307457 40547466SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 1, 11:20 PM EDT | Mesoscale Discussion | SPC | Bronx, Kings, Nassau, New York, Queens, Suffolk and 1 more | 85 min |
Nearby
Mesoscale Discussions in New York, 2021Mesoscale Discussions in New Jersey, 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.