Alert archive / Georgia / Flash Flood Warnings in 2009

Flash Flood Warning 31, NWS Atlanta, GA

September 20, 2009Cherokee County, Georgia

NWS Atlanta, GA issued this flash flood warning at Sep 20, 2009, 2:45 PM EDT for Cherokee County, Georgia. It was in force for 6 hr. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Sep 20, 2009, 2:45 PM EDT (18:45 UTC)
Expired: Sep 20, 2009, 8:45 PM EDT
In force: 6 hr
Issued by: NWS Atlanta, GA
Area: Storm-based polygon
Flood severity: None

County Cherokee County, GA

The radar

The Atlanta radar (KFFC), 98 km from the middle of the area, began a volume at 18:44 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

Peachtre/Fal Fld, GA (KFFC), launched 12:00Z, 6.8 hours before the alert went out and 97 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: 977 J/kg
Mixed-layer CIN: -26 J/kg
Mixed-layer LCL: 520 m above ground
0-6 km bulk shear: 12 kt
0-1 km storm-relative helicity: 52 m²/s²
0-3 km storm-relative helicity: 132 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.

000 
WGUS52 KFFC 201845
FFWFFC
GAC057-210045-
/O.NEW.KFFC.FF.W.0031.090920T1845Z-090921T0045Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
245 PM EDT SUN SEP 20 2009

THE NATIONAL WEATHER SERVICE IN PEACHTREE CITY HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  CHEROKEE COUNTY IN NORTH CENTRAL GEORGIA

* UNTIL 845 PM EDT

* AT 240 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
  VERY HEAVY RAIN FROM A THUNDERSTORM NEAR HOLLY SPRINGS..MOVING
  NORTHEAST AT 10 MPH. RAINFALL AMOUNTS OF TWO INCHES IN THE PAST
  TWO HOURS...HAVE OCCURRED IN THE SOUTHWEST PORTION OF CHEROKEE
  COUNTY...JUST WEST OF WOODSTOCK NEAR LAKE ALLATOONA. ADDITIONAL 
  THUNDERSTORMS WILL BE MOVING OVER THE SAME AREAS WITHIN THE NEXT
  FEW HOURS...AND AN ADDITIONAL ONE TO TWO INCHES OF RAIN CAN BE
  EXPECTED.

* OTHER LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO
  CANTON...BUFFINGTON...WALESKA AND BALL GROUND. KELLOGG CREEK...
  NOONDAY CREEK...AND ROSE CREEK WILL BE AFFECTED.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

EXCESSIVE RUNOFF FROM HEAVY RAINFALL WILL CAUSE FLOODING OF SMALL
CREEKS AND STREAMS...AS WELL AS HIGHWAYS AND UNDERPASSES.
ADDITIONALLY...COUNTRY ROADS AND FARMLANDS ALONG THE BANKS OF
CREEKS...STREAMS AND OTHER LOW LYING AREAS ARE SUBJECT TO FLOODING.

FLOODING IS OCCURRING OR IS IMMINENT. IT IS IMPORTANT TO KNOW WHERE
YOU ARE RELATIVE TO STREAMS...RIVERS...OR CREEKS WHICH CAN BECOME
KILLERS IN HEAVY RAINS. CAMPERS AND HIKERS SHOULD AVOID STREAMS OR
CREEKS.

IF YOU SEE SIGNIFICANT FLOODING CALL THE NATIONAL WEATHER SERVICE
TOLL FREE AT 1 8 6 6 7 6 3 4 4 6 6.

&&

LAT...LON 3440 8457 3438 8457 3439 8445 3437 8426
      3409 8443 3409 8459 3411 8459 3411 8463
      3409 8463 3409 8466 3421 8466 3422 8464
      3430 8465 3441 8462

$$

The office that day

Everything else NWS Atlanta, GA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 20, 5:37 AM EDT	Flash Flood Warning	FFC	Lumpkin	6 hr
Sep 20, 6:34 AM EDT	Flash Flood Warning	FFC	Union	6 hr
Sep 20, 6:43 AM EDT	Flash Flood Warning	FFC	White	6 hr
Sep 20, 7:40 AM EDT	Flash Flood Warning	FFC	Towns	6 hr
Sep 20, 11:23 AM EDT	Areal Flood Warning	FFC	Lumpkin	112 min
Sep 20, 11:59 AM EDT	River Flood Warning	FFC	Clarke, Greene, Oconee	5 days
Sep 20, 12:23 PM EDT	Areal Flood Warning	FFC	Union, White	52 min
Sep 20, 1:17 PM EDT	Areal Flood Warning	FFC	Lumpkin, Towns, Union, White	6 hr
Sep 20, 1:51 PM EDT	Areal Flood Warning	FFC	Cobb	6 hr
Sep 20, 5:35 PM EDT	River Flood Warning	FFC	Dawson, Forsyth	38 hr
Sep 20, 6:32 PM EDT	Flash Flood Warning	FFC	Catoosa, Walker	6 hr
Sep 20, 6:56 PM EDT	Flash Flood Warning	FFC	Paulding	4 hr
Sep 20, 7:14 PM EDT	Flash Flood Warning	FFC	Cobb	4 hr

Nearby

Flash Flood Warnings in Georgia, 2009 Every flash flood warning in 2009

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.