Alert archive / Pennsylvania / Tornado Watches in 2010
Tornado Watch 689
The Storm Prediction Center issued this tornado watch at Sep 30, 2010, 12:39 PM EDT for Kent County, New Castle County, Sussex County, Delaware; 13 counties in Maryland; 15 counties in Pennsylvania. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 30, 2010, 12:39 PM EDT (16:39 UTC)
- Expired
- Sep 30, 2010, 7:00 PM EDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 0.5 in
- Strongest gust expected
- 60 kt
All 31 counties
Kent County, DE, New Castle County, DE, Sussex County, DE, Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Caroline County, MD, Cecil County, MD, Charles County, MD, City of Baltimore, MD, Harford County, MD, Kent County, MD, Prince George's County, MD, Queen Anne's County, MD, Saint Mary's County, MD, Talbot County, MD, Berks County, PA, Bucks County, PA, Carbon County, PA, Chester County, PA, Dauphin County, PA, Delaware County, PA, Lancaster County, PA, Lebanon County, PA, Lehigh County, PA, Monroe County, PA, Montgomery County, PA, Northampton County, PA, Philadelphia County, PA, Schuylkill County, PA, York County, PA
The radar
The Dover AFB radar (KDOX), 130 km from the middle of the area, began a volume at 16:39 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
- 20%
- 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
- 50%
Warnings issued inside it
4 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 30, 1:42 PM EDT | Flash Flood Warning | CTP | Lancaster, Lebanon, Schuylkill, York | 6 hr |
| Sep 30, 4:30 PM EDT | Flash Flood Warning | LWX | Anne Arundel, Calvert, Saint Mary's | 6 hr |
| Sep 30, 6:13 PM EDT | Flash Flood Warning | LWX | Anne Arundel, Baltimore, Calvert, Carroll, Charles, Harford and 5 more | 6 hr |
| Sep 30, 6:41 PM EDT | Severe Thunderstorm Warning | CTP | Columbia, Dauphin, Lebanon, Montour, Northumberland, Schuylkill | 49 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
Washington/Dulle, VA (KIAD), launched 12:00Z, 4.7 hours before the alert went out and 142 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
- 47 J/kg
- Mixed-layer CIN
- -41 J/kg
- Mixed-layer LCL
- 449 m above ground
- 0-6 km bulk shear
- 77 kt
- 0-1 km storm-relative helicity
- 514 m²/s²
- 0-3 km storm-relative helicity
- 665 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 1.3
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 30, 4:02 AM EDT | Mesoscale Discussion | SPC | Kent, Sussex | 118 min |
| Sep 30, 4:55 AM EDT | Tornado Watch | SPC | Kent, New Castle, Sussex | 8 hr |
| Sep 30, 8:25 AM EDT | Mesoscale Discussion | SPC | Kent, New Castle, Sussex | 95 min |
| Sep 30, 10:49 AM EDT | Mesoscale Discussion | SPC | Kent, New Castle, Sussex | 116 min |
| Sep 30, 3:16 PM EDT | Mesoscale Discussion | SPC | Kent, New Castle, Sussex | 119 min |
| Sep 30, 5:43 PM EDT | Mesoscale Discussion | SPC | Somerset | 92 min |
| Sep 29, 9:39 PM EDT | Tornado Watch | SPC | Isle of Wight, James City, Southampton, Surry, Sussex, York and 8 more | 7 hr |
| Sep 30, 12:47 AM EDT | Mesoscale Discussion | SPC | Isle of Wight, Southampton, City of Chesapeake, City of Franklin, City of Norfolk, City of Portsmouth and 2 more | 88 min |
Nearby
Tornado Watches in Pennsylvania, 2010Tornado Watches in Maryland, 2010Tornado Watches in Delaware, 2010Every tornado watch in 2010
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.