Alert archive / New York / Flash Flood Warnings in 2021

Flash Flood Warning 35, NWS New York, NY

August 28, 2021Suffolk County, New York

NWS New York, NY issued this flash flood warning at Aug 28, 2021, 3:40 AM EDT for Suffolk County, New York. It was in force for 3 hr. 3 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued
Aug 28, 2021, 3:40 AM EDT (07:40 UTC)
Expired
Aug 28, 2021, 6:29 AM EDT
In force
3 hr
Issued by
NWS New York, NY
Area
Storm-based polygon
Flood severity
None

County Suffolk County, NY

The radar

The Brookhaven radar (KOKX), 30 km from the middle of the area, began a volume at 07:40 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 was reported inside it

TimeReportWhereRemark
Aug 28, 4:05 AM EDTFLASH FLOOD1 Sse Saint James, NYFLOODING RESULTING IN CARS BEING STUCK ON ROUTE 25 IN SMITHTOWN.
Aug 28, 4:10 AM EDTFLASH FLOOD1 Se Nesconset, NYFLOODING REPORTED RESULTING IN IMPASSABLE ROADS AT OLD NICHOLS ROAD AND ROLLING HILLS DRIVE IN LAKE RONKONKOMA.
Aug 28, 4:20 AM EDTFLASH FLOOD1 S Saint James, NYFIRE DEPARTMENT RESCUING PEOPLE FROM VEHICLES ON ROUTE 25, JUST WEST OF ROUTE 347.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Brookhaven, NY (KOKX), launched 00:00Z, 7.7 hours before the alert went out and 30 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-pSkew-T log-p diagram, Brookhaven, NY at 00:00Z on 2021-08-28Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 2057 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Brookhaven, NY at 00:00Z on 2021-08-28The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 14 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
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
2057 J/kg
Mixed-layer CIN
-25 J/kg
Mixed-layer LCL
1094 m above ground
0-6 km bulk shear
20 kt
0-1 km storm-relative helicity
14 m²/s²
0-3 km storm-relative helicity
13 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

955 
WGUS51 KOKX 280740
FFWOKX
NYC103-281100-
/O.NEW.KOKX.FF.W.0035.210828T0740Z-210828T1100Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service New York NY
340 AM EDT Sat Aug 28 2021

The National Weather Service in Upton has issued a

* Flash Flood Warning for...
  Western Suffolk County in southeastern New York...

* Until 700 AM EDT.

* At 340 AM EDT, Doppler radar and automated rain gauges indicated 
  thunderstorms producing heavy rain across the warned area. Between 
  1.5 and 3 inches of rain have fallen. The expected rainfall rate 
  is 1 to 2 inches in 1 hour. Flash flooding is ongoing or expected 
  to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar and automated gauges.

  IMPACT...Flash flooding of small creeks and streams, urban
           areas, highways, streets and underpasses as well as
           other poor drainage and low-lying areas.

* Some locations that will experience flash flooding include...
  Islip, Brentwood, Commack, Deer Park, Hauppauge, Ronkonkoma, Stony 
  Brook, Babylon, Patchogue, Northport, Robert Moses State Park, 
  Holbrook, Dix Hills, Smithtown, Bay Shore, Sayville, Centerport, 
  Captree State Park, Davis Park and Central Islip.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood 
deaths occur in vehicles.

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

&&

LAT...LON 4092 7339 4092 7322 4095 7314 4089 7311
      4074 7296 4074 7301 4072 7302 4071 7312
      4068 7314 4070 7320 4069 7324 4067 7327
      4066 7316 4072 7297 4067 7300 4061 7326
      4067 7331 4067 7328 4068 7332 4076 7341

FLASH FLOOD...RADAR AND GAUGE INDICATED
EXPECTED RAINFALL...1-2 INCHES IN 1 HOUR

$$

JE
2 follow-up statements
937 
WGUS71 KOKX 280959
FFSOKX

Flash Flood Statement
National Weather Service New York NY
559 AM EDT Sat Aug 28 2021

NYC103-281100-
/O.CON.KOKX.FF.W.0035.000000T0000Z-210828T1100Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Suffolk NY-
559 AM EDT Sat Aug 28 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 7 AM EDT THIS MORNING 
FOR WESTERN SUFFOLK COUNTY...

At 559 AM EDT, Flood waters have begun to recede. The heavy rain has 
ended. Additional flooding is not expected, but some roadways may 
remain closed, especially in the vicinity of Smithtown, Saint James, 
Nesconset, and Ronkonkoma. Please continue to heed the remaining 
road closures.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Radar and automated gauges and reports from law
         enforcement.

IMPACT...Flash flooding of urban areas, highways, streets and
         underpasses as well as other poor drainage and low-lying
         areas.

Some locations that will experience flash flooding include...
  Islip, Brentwood, Commack, Deer Park, Hauppauge, Ronkonkoma, Stony 
  Brook, Babylon, Patchogue, Northport, Robert Moses State Park, 
  Holbrook, Dix Hills, Smithtown, Bay Shore, Sayville, Centerport, 
  Captree State Park, Davis Park and Central Islip.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood 
deaths occur in vehicles.

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.and

&&

LAT...LON 4092 7339 4092 7322 4095 7314 4089 7311
      4074 7296 4074 7301 4072 7302 4071 7312
      4068 7314 4070 7320 4069 7324 4067 7327
      4066 7316 4072 7297 4067 7300 4061 7326
      4067 7331 4067 7328 4068 7332 4076 7341

FLASH FLOOD...RADAR AND GAUGE INDICATED
EXPECTED RAINFALL...1-2 INCHES IN 1 HOUR

$$

JE
588 
WGUS71 KOKX 281029
FFSOKX

Flash Flood Statement
National Weather Service New York NY
629 AM EDT Sat Aug 28 2021

NYC103-281039-
/O.CAN.KOKX.FF.W.0035.000000T0000Z-210828T1100Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Suffolk NY-
629 AM EDT Sat Aug 28 2021

...FLASH FLOOD WARNING IS CANCELLED FOR WESTERN SUFFOLK COUNTY...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Please continue to heed remaining road closures.

LAT...LON 4092 7339 4092 7322 4095 7314 4089 7311
      4074 7296 4074 7301 4072 7302 4071 7312
      4068 7314 4070 7320 4069 7324 4067 7327
      4066 7316 4072 7297 4067 7300 4061 7326
      4067 7331 4067 7328 4068 7332 4076 7341

$$

JP

The office that day

Everything else NWS New York, NY issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 28, 2:57 AM EDTAreal Flood AdvisoryOKXSuffolk43 min
Aug 28, 4:25 AM EDTAreal Flood AdvisoryOKXSuffolk2 hr
Aug 28, 5:00 AM EDTFlash Flood WarningOKXSuffolk95 min
Aug 28, 5:48 AM EDTAreal Flood AdvisoryOKXKings, Nassau, Queens, Suffolk117 min
Aug 28, 1:49 PM EDTAreal Flood AdvisoryOKXSuffolk86 min
Aug 28, 3:24 PM EDTAreal Flood AdvisoryOKXNassau, Suffolk81 min

Nearby

Flash Flood Warnings in New York, 2021Every flash flood warning 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.