Alert archive / New York / Tornado Watches in 2011

Tornado Watch 813

August 28, 20114 states

The Storm Prediction Center issued this tornado watch at Aug 28, 2011, 4:38 AM EDT for 4 states. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued: Aug 28, 2011, 4:38 AM EDT (08:38 UTC)
Expired: Aug 28, 2011, 9:54 AM EDT
In force: 5 hr
Issued by: the Storm Prediction Center
Strongest gust expected: 60 kt

Counties Greater Bridgeport Planning Region, CT, Lower Connecticut River Valley Planning Region, CT, Naugatuck Valley Planning Region, CT, Southeastern Connecticut Planning Region, CT, Bergen County, NJ, Hudson County, NJ, Passaic County, NJ, Bronx County, NY, Kings County, NY, Nassau County, NY, New York County, NY, Putnam County, NY, Queens County, NY, Richmond County, NY, Rockland County, NY, Suffolk County, NY, Westchester County, NY, Bristol County, RI, Newport County, RI, Washington County, RI

The radar

The Brookhaven radar (KOKX), 34 km from the middle of the area, began a volume at 08:39 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.

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes: 30%
One or more EF2 to EF5 tornadoes: 20%
Ten or more severe wind reports: 10%
One or more gusts of 65 knots or more: 10%
Ten or more severe hail reports: 5%
One or more hailstones of 2 inches or more: 5%
Six or more combined severe hail and wind reports: 20%

Warnings issued inside it

1 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
Aug 28, 4:46 AM EDT	Tornado Warning	OKX	Nassau, Suffolk	29 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Brookhaven, NY (KOKX), launched 00:00Z, 8.6 hours before the alert went out and 34 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 957 J/kg
Mixed-layer CIN: -1 J/kg
Mixed-layer LCL: 466 m above ground
0-6 km bulk shear: 14 kt
0-1 km storm-relative helicity: 110 m²/s²
0-3 km storm-relative helicity: 269 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

109 
WWUS20 KWNS 280841
SEL3
SPC WW 280841
CTZ000-NJZ000-NYZ000-RIZ000-CWZ000-281500-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 813
NWS STORM PREDICTION CENTER NORMAN OK
440 AM EDT SUN AUG 28 2011

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

       SOUTHERN CONNECTICUT
       EXTREME NORTHEASTERN NEW JERSEY
       EXTREME SOUTHEASTERN NEW YORK AND LONG ISLAND
       SOUTHERN RHODE ISLAND
       COASTAL WATERS

EFFECTIVE THIS SUNDAY MORNING FROM 440 AM UNTIL 1100 AM EDT.

TORNADOES...THUNDERSTORM WIND GUSTS TO 70 MPH...AND DANGEROUS
LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 40 STATUTE
MILES EITHER SIDE OF A LINE FROM 25 MILES NORTHWEST OF NEW YORK
CITY NEW YORK TO 25 MILES EAST NORTHEAST OF BLOCK ISLAND RHODE
ISLAND.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED
WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.

OTHER WATCH INFORMATION...THIS TORNADO WATCH REPLACES TORNADO
WATCH NUMBER 812. WATCH NUMBER 812 WILL NOT BE IN EFFECT AFTER
440 AM EDT.

DISCUSSION...MRGL TORNADO POTENTIAL IS FCST TO SHIFT NEWD ACROSS WW
AREA IN STEP WITH TRANSLATION OF FAVORABLE SECTOR OF HURRICANE
IRENE...ASSOCIATED WITH CELLS EMBEDDED IN MIDDLE-OUTER CONVECTIVE
BANDS AND MOVING NWWD/ONSHORE.  AMIDST WIDESPREAD FAVORABLE
LOW-LEVEL HODOGRAPHS...AIR MASS WILL STABILIZE SUBSTANTIALLY WITH
INLAND EXTENT...REDUCING TORNADO THREAT WITH DISTANCE AWAY FROM
COAST AS PER SPC MESOSCALE DISCUSSION 2073.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH EXTREME
TURBULENCE AND SURFACE WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI
WITH MAXIMUM TOPS TO 500. MEAN STORM MOTION VECTOR 13045.


...EDWARDS

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Lasted
Aug 28, 12:30 AM EDT	Mesoscale Discussion	SPC	90 min
Aug 28, 4:01 AM EDT	Mesoscale Discussion	SPC	89 min
Aug 28, 8:09 AM EDT	Mesoscale Discussion	SPC	2 hr

Nearby

Tornado Watches in New York, 2011 Tornado Watches in Connecticut, 2011 Tornado Watches in New Jersey, 2011 Every tornado watch in 2011

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.