Back-to-back powerful Pacific storm systems to impact the Pacific Northwest and northern California through the end of this week with heavy rain, flooding, strong winds, and higher elevation mountain snow. A strong, long-duration atmospheric river will accompany the Pacific storms, bringing excessive rainfall and flash flooding to southwest Oregon and northwest California through the week. Read More >
Overview
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After a significant heatwave, a cold front approached the mid-Atlantic on July 1, 2021. A potent mid-level trough was also digging southward through southern Ontario and into the Great Lakes region, and a strong upper level jet streak was present downstream the trough axis, over the interior mid-Atlantic and northern New England. This strong upper level forcing combined with the approaching front and a lingering warm, moist air mass ahead of it caused widespread thunderstorm development on July 1. Storms occurred almost exclusively south of Interstate 78, in the environment of best instability. A number of storms became severe, taking the form of mainly linear and multi-cellular clusters but with some embedded supercellular characteristics. Straight line wind damage was the primary hazard, with a number of reports of downed trees and power outages due to winds. In addition, two confirmed EF-1 tornadoes occurred over southern Delaware. A remnant outflow boundary from earlier storms to the north, combined with sea/bay breezes in the area, likely caused a localized enhancement of low level wind shear and created a corridor of enhanced tornado potential. Another area of rotation over far eastern Pennsylvania and central New Jersey also prompted a couple of Tornado Warnings, but no evidence of tornadic damage was found in these areas. With the cold front remaining to the west, some storm activity continued into the overnight, but storm coverage and intensity gradually waned with the loss of daytime heating and the overturning of the atmosphere from earlier storms. |
 KDOX radar loop from 4:43PM to 5:15PM on July 1, 2021, featuring the two EF-1 tornadoes in Delaware. Correlation coefficient and differential reflectivity panels show evidence of tornadic debris signatures. |
Synoptic Overview at 12z 1 Jul 2021 (courtesy of SPC)
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| Figure 1: 250-mb analysis | Figure 2: 300-mb analysis | Figure 3: 500-mb analysis |
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| Figure 4: 700-mb analysis | Figure 5: 850-mb analysis | Figure 6: 925-mb analysis |
Synoptic Overview at 00z 2 Jul 2021 (courtesy of SPC)
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| Figure 7: 250-mb analysis | Figure 8: 300-mb analysis | Figure 9: 500-mb analysis |
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| Figure 10: 700-mb analysis | Figure 11: 850-mb analysis | Figure 12: 925-mb analysis |
Surface Maps (courtesy of WPC)
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| Figure 13: 12z surface map | Figure 14: 15z surface map | Figure 15: 18z surface map |
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| Figure 16: 21z surface map | Figure 17: 00z surface map | Figure 18: 03z surface map |
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| Figure 19: 12z Long Island, NY sounding | Figure 20: 12z Sterling, VA sounding | Figure 21: 12z Wallops Island, VA sounding |
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| Figure 19: 12z Albany, NY sounding (Long Island was unavailable) | Figure 20: 12z Sterling, VA sounding | Figure 21: 12z Wallops Island, VA sounding |
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| Figure 1: National Preliminary Reports 12z 31 Mar 2022 to 12z 1 Apr 2022 | Figure 2: Zoomed Preliminary Reports for the same period. | Preliminary reports vs 1630z Day 1 SPC outlook. |
Click here for a county warning area based plot of local storm reports and warnings/advisories issued for the 1 Jul 2021 event.
PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
503 AM EDT FRI JUL 2 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0313 PM TSTM WND DMG 4 NNE WEST SADSBURY TWP 40.04N 75.92W
07/01/2021 CHESTER PA COUNTY OFFICIAL
DOWNED TREE ON LAMMEY ROAD. TIME ESTIMATED
FROM RADAR.
0321 PM TSTM WND DMG 2 NNW GERYVILLE 40.45N 75.48W
07/01/2021 LEHIGH PA UTILITY COMPANY
DOWNED WIRES NEAR ELM ROAD. TIME ESTIMATED
FROM RADAR.
0321 PM TSTM WND DMG 2 WNW CALN TWP 40.01N 75.78W
07/01/2021 CHESTER PA COUNTY OFFICIAL
DOWNED TREE ON FISHERVILLE ROAD. TIME
ESTIMATED FROM RADAR.
0323 PM TSTM WND DMG 2 SW GILBERTSVILLE 40.30N 75.64W
07/01/2021 MONTGOMERY PA PUBLIC
MPING REPORT OF DOWNED TREE LIMBS AND POWER
LINES NEAR ROUTE 100. TIME ESTIMATED FROM
RADAR.
0327 PM TSTM WND DMG 1 NE THORNDALE 40.01N 75.73W
07/01/2021 CHESTER PA COUNTY OFFICIAL
DOWNED TREE ON BEAVER RUN ROAD. TIME
ESTIMATED FROM RADAR.
0331 PM TSTM WND DMG 1 W CHESTER SPRINGS 40.10N 75.64W
07/01/2021 CHESTER PA UTILITY COMPANY
DOWNED WIRES NEAR HORSESHOE TRAIL. TIME
ESTIMATED FROM RADAR.
0351 PM TSTM WND DMG 1 WNW VALLEY FORGE 40.11N 75.48W
07/01/2021 CHESTER PA UTILITY COMPANY
SEVERAL REPORTS OF DOWNED TREE LIMBS AND
WIRES NEAR VALLEY FORGE AND PHOENIXVILLE.
TIME ESTIMATED FROM RADAR.
0400 PM TSTM WND DMG 2 SSW STEVENSVILLE 38.97N 76.33W
07/01/2021 QUEEN ANNE'S MD DEPT OF HIGHWAYS
TREES AND UTILITY WIRES DOWN WITH DEBRIS ON
THE ROADWAY ALONG MARYLAND ROUTE 8 SOUTH OF
KENT MANOR DRIVE.
0412 PM TSTM WND DMG 1 E CONSHOHOCKEN 40.08N 75.28W
07/01/2021 MONTGOMERY PA COUNTY OFFICIAL
DOWNED TREE LIMBS ON JOSHUA ROAD NEAR CEDAR
GROVE ROAD. TIME ESTIMATED FROM RADAR.
0419 PM TSTM WND DMG 2 SSE TEMPLEVILLE 39.11N 75.75W
07/01/2021 CAROLINE MD UTILITY COMPANY
SEVERAL REPORTS OF DOWNED TREE LIMBS AND
WIRES BETWEEN MARYDEL AND HARTLY. TIME
ESTIMATED FROM RADAR.
0421 PM TSTM WND DMG FEDERALSBURG 38.69N 75.77W
07/01/2021 CAROLINE MD UTILITY COMPANY
SEVERAL REPORTS OF POWER LINES DOWN AND
NUMEROUS POWER OUTAGES IN THE FEDERALSBURG
AREA. TIME ESTIMATED FROM RADAR.
0424 PM TSTM WND DMG CENTREVILLE 39.05N 76.07W
07/01/2021 QUEEN ANNE'S MD UTILITY COMPANY
SEVERAL REPORTS OF WIRES DOWN NEAR
CENTREVILLE. TIME ESTIMATED FROM RADAR.
0426 PM TSTM WND DMG 1 E HARTLY 39.17N 75.68W
07/01/2021 KENT DE UTILITY COMPANY
DOWNED TREE LIMBS AND WIRES EAST OF HARTLY.
TIME ESTIMATED FROM RADAR.
0430 PM TSTM WND DMG 1 NE JENKINTOWN 40.10N 75.12W
07/01/2021 MONTGOMERY PA COUNTY OFFICIAL
DOWNED TREE ON WIRES NEAR THE INTERSECTION
OF WASHINGTON LANE AND PEPPER ROAD. TIME
ESTIMATED FROM RADAR.
0430 PM TSTM WND DMG 2 NNW FEDERALSBURG 38.72N 75.79W
07/01/2021 CAROLINE MD DEPT OF HIGHWAYS
TREES AND UTILITY WIRES DOWN WITH DEBRIS ON
THE ROADWAY ALONG MARYLAND ROUTE 313 NEAR
OLD DENTON ROAD.
0435 PM TSTM WND DMG 2 SW STARKEY CORNER 39.10N 76.03W
07/01/2021 QUEEN ANNE'S MD DEPT OF HIGHWAYS
TREES AND UTILITY WIRES DOWN WITH DEBRIS ON
THE ROADWAY ALONG MARYLAND ROUTE 213 NEAR
HATCHETT ROAD.
0435 PM TSTM WND DMG DENTON 38.89N 75.83W
07/01/2021 CAROLINE MD UTILITY COMPANY
DOWNED WIRES IN THE DENTON AREA. TIME
ESTIMATED FROM RADAR.
0435 PM TSTM WND DMG 2 N SMITHVILLE 38.80N 75.73W
07/01/2021 CAROLINE MD DEPT OF HIGHWAYS
TREES AND UTILITY LINES DOWN WITH DEBRIS ON
THE ROADWAY ALONG MARYLAND ROUTE 404 AND
BREEDING ROAD.
0442 PM TSTM WND DMG 4 WSW SEAFORD 38.62N 75.68W
07/01/2021 SUSSEX DE UTILITY COMPANY
DOWNED TREES AND POWER LINES NEAR WOODPECKER
ROAD. TIME ESTIMATED FROM RADAR.
0442 PM TSTM WND DMG 2 SSW WOODSIDE 39.04N 75.57W
07/01/2021 KENT DE UTILITY COMPANY
SEVERAL REPORTS OF DOWNED TREE LIMBS AND
WIRES NORTH OF FELTON. TIME ESTIMATED FROM
RADAR.
0445 PM FLOOD 1 SW CAMDEN 39.11N 75.55W
07/01/2021 KENT DE DEPT OF HIGHWAYS
FLOODING AT SOUTH MAIN STREET AND SOUTH
STREET.
0448 PM TSTM WND DMG TACONY 40.03N 75.05W
07/01/2021 PHILADELPHIA PA PUBLIC
MPING REPORT OF WIND DAMAGE NEAR JACKSON
STREET. TIME ESTIMATED FROM RADAR.
0450 PM TSTM WND DMG 1 NE FEASTERVILLE-TREVO 40.15N 74.95W
07/01/2021 BUCKS PA DEPT OF HIGHWAYS
TREE DOWN ON U.S. ROUTE 1.
0450 PM TSTM WND DMG 2 SW SEAFORD 38.62N 75.64W
07/01/2021 SUSSEX DE UTILITY COMPANY
DOWNED TREE LIMBS AND WIRES NEAR CRAIGS MILL
ROAD AND WOODLAND ROAD. TIME ESTIMATED FROM
RADAR.
0452 PM TSTM WND DMG HARRINGTON 38.92N 75.57W
07/01/2021 KENT DE DEPT OF HIGHWAYS
TREES AND UTILITY LINES DOWN WITH DEBRIS IN
THE ROADWAY.
0452 PM TSTM WND DMG 2 NNE FARMINGTON 38.90N 75.57W
07/01/2021 KENT DE EMERGENCY MNGR
TREES DOWN AND VEHICLES BLOWN OFF THE ROAD
ALONG U.S ROUTE 13 AROUND TOWER HILL ROAD.
0453 PM TSTM WND DMG LEVITTOWN 40.16N 74.89W
07/01/2021 BUCKS PA UTILITY COMPANY
SEVERAL REPORTS OF DOWNED TREE LIMBS AND
WIRES IN LEVITTOWN. TIME ESTIMATED FROM
RADAR.
0453 PM TSTM WND DMG 3 NE BRIDGEVILLE 38.77N 75.57W
07/01/2021 SUSSEX DE UTILITY COMPANY
SEVERAL REPORTS OF DOWNED TREES AND WIRES
NORTHEAST OF BRIDGEVILLE. TIME ESTIMATED
FROM RADAR.
0453 PM TSTM WND DMG SEAFORD 38.64N 75.61W
07/01/2021 SUSSEX DE FIRE DEPT/RESCUE
DOWNED WIRES ON HALL STREET, ALDER LANE, AND
NEAR THE INTERSECTION OF NEALS SCHOOL ROAD
AND BOYCE ROAD IN SEAFORD. TIME ESTIMATED
FROM RADAR.
0458 PM TSTM WND DMG 2 SW HOUSTON 38.90N 75.53W
07/01/2021 KENT DE UTILITY COMPANY
DOWNED TREES AND WIRES NEAR THISTLEWOOD
ROAD. TIME ESTIMATED FROM RADAR.
0459 PM TSTM WND DMG 1 SE FAIRLESS HILLS 40.17N 74.84W
07/01/2021 BUCKS PA UTILITY COMPANY
SEVERAL REPORTS OF DOWNED POWER LINES NEAR
FAIRLESS HILLS. TIME ESTIMATED FROM RADAR.
0500 PM TSTM WND DMG 2 WSW HOUSTON 38.90N 75.54W
07/01/2021 KENT DE PUBLIC
ROOF DAMAGE TO A MOBILE HOME ON HUNTING
QUARTER ROAD NEAR WILLIAMSVILLE, DE. TIME
ESTIMATED FROM RADAR. SOCIAL MEDIA REPORT.
0502 PM TORNADO 3 ENE MILFORD 38.93N 75.37W
07/01/2021 SUSSEX DE TRAINED SPOTTER
SIGNIFICANT TREE DAMAGE WITH SOME TREES INTO
HOUSES.
0503 PM TSTM WND DMG 2 E MILFORD 38.91N 75.40W
07/01/2021 SUSSEX DE TRAINED SPOTTER
SEVERAL LARGE TREES DOWNED. TIME ESTIMATED
FROM RADAR.
0505 PM TSTM WND GST 1 E MILFORD 38.91N 75.42W
07/01/2021 M46 MPH SUSSEX DE MESONET
0506 PM TSTM WND DMG 3 ESE ALLOWAY 39.54N 75.29W
07/01/2021 SALEM NJ UTILITY COMPANY
DOWNED POWER LINES NEAR ALLOWAY FRIESBURG
ROAD. TIME ESTIMATED FROM RADAR.
0509 PM TSTM WND GST 6 SSE BIG STONE BEACH 38.91N 75.30W
07/01/2021 M80 MPH SUSSEX DE PUBLIC
PERSONAL WEATHER STATION KDEMILFO30. GUST
WAS MEASURED IN VERY CLOSE PROXIMITY TO A
LIKELY TORNADO.
0516 PM TSTM WND GST LEWES 38.78N 75.13W
07/01/2021 M56 MPH SUSSEX DE MESONET
WEATHERFLOW.
0518 PM TSTM WND GST 1 ENE LEWES 38.78N 75.12W
07/01/2021 M64 MPH SUSSEX DE MESONET
NOS GAUGE LWSD1.
0519 PM TSTM WND DMG 2 WSW YARDVILLE 40.17N 74.70W
07/01/2021 BURLINGTON NJ FIRE DEPT/RESCUE
DOWNED WIRES ON GRAND AVENUE. TIME ESTIMATED
FROM RADAR.
0519 PM TSTM WND DMG STOCKLEY 38.64N 75.31W
07/01/2021 SUSSEX DE UTILITY COMPANY
DOWNED POWER POLES AND WIRES NEAR MORRIS
MILL ROAD. TIME ESTIMATED FROM RADAR.
0524 PM MARINE TSTM WIND BRANDYWINE SHOAL LIGHT 38.99N 75.11W
07/01/2021 M68 MPH ANZ431 NJ OTHER FEDERAL
NOS GAUGE BRND1.
0524 PM TSTM WND GST 1 ENE LEWES 38.78N 75.12W
07/01/2021 M61 MPH SUSSEX DE MESONET
NOS GAUGE LWSD1.
0530 PM MARINE TSTM WIND 1 SSW NORTH CAPE MAY 38.97N 74.96W
07/01/2021 M52 MPH CAPE MAY NJ MESONET
NOS GAUGE CMAN4.
0530 PM MARINE TSTM WIND 1 NE LEWES 38.78N 75.12W
07/01/2021 M50 MPH ANZ431 DE MESONET
CAPE HENLOPEN WEATHERFLOW SITE.
0532 PM TSTM WND GST CAPE MAY 38.94N 74.91W
07/01/2021 M45 MPH CAPE MAY NJ MESONET
WEATHERFLOW.
0535 PM TSTM WND DMG WOODBINE 39.24N 74.81W
07/01/2021 CAPE MAY NJ UTILITY COMPANY
SEVERAL REPORTS OF DOWNED POWER LINES IN THE
AREA. TIME ESTIMATED FROM RADAR.
0538 PM MARINE TSTM WIND INDIAN BEACH 38.68N 75.08W
07/01/2021 M45 MPH ANZ455 DE MESONET
WEATHERFLOW SITE XDEW.
0549 PM MARINE TSTM WIND 1 NNW SEA ISLE CITY 39.18N 74.70W
07/01/2021 M50 MPH ANZ453 NJ MESONET
WEATHERFLOW GAUGE XLUD.
0555 PM TSTM WND GST 2 SE WOODBINE 39.22N 74.79W
07/01/2021 M46 MPH CAPE MAY NJ MESONET
0555 PM TSTM WND GST 2 ENE DENNISVILLE 39.20N 74.78W
07/01/2021 M48 MPH CAPE MAY NJ MESONET
0602 PM TSTM WND DMG 1 S MARLBORO 40.30N 74.24W
07/01/2021 MONMOUTH NJ UTILITY COMPANY
A FEW REPORTS OF DOWNED TREES AND WIRES NEAR
DUTCH LANE ROAD AND AUSTEN COURT. TIME
ESTIMATED FROM RADAR.
0605 PM TSTM WND GST CAPE HENLOPEN BEACH 38.80N 75.09W
07/01/2021 M49 MPH SUSSEX DE MESONET
0620 PM TSTM WND DMG 2 ESE LEISURE VILLAGE E 40.03N 74.12W
07/01/2021 OCEAN NJ UTILITY COMPANY
SEVERAL REPORTS OF DOWNED WIRES IN BRICK
TOWNSHIP AND THE LEISURE VILLAGE EAST AREA.
TIME ESTIMATED FROM RADAR.
0625 PM TSTM WND DMG 2 NNW WANAMASSA 40.25N 74.04W
07/01/2021 MONMOUTH NJ UTILITY COMPANY
SEVERAL REPORTS OF DOWNED POWER LINES IN THE
WANAMASSA AND DEAL AREAS. TIME ESTIMATED
FROM RADAR.
0630 PM MARINE TSTM WIND 1 WSW LAVALLETTE 39.96N 74.09W
07/01/2021 M39 MPH ANZ451 NJ PUBLIC
MEASURED BY A TEMPEST WEATHER STATION NEAR
PERSHING BLVD.
0632 PM TSTM WND DMG 4 SE BRIDGEVILLE 38.70N 75.55W
07/01/2021 SUSSEX DE UTILITY COMPANY
SEVERAL REPORTS OF TREES AND WIRES DOWN NEAR
ROUTE 18 SOUTHEAST OF BRIDGEVILLE. TIME
ESTIMATED FROM RADAR.
0640 PM FLOOD SPRING LAKE HEIGHTS 40.15N 74.04W
07/01/2021 MONMOUTH NJ DEPT OF HIGHWAYS
FLOODING ALONG NEW JERSEY ROUTE 71 AT WARREN
AVENUE.
0642 PM MARINE TSTM WIND 2 E WARETOWN 39.79N 74.17W
07/01/2021 M40 MPH ANZ451 NJ MESONET
KITE ISLAND WEATHERFLOW GAUGE.
0644 PM TSTM WND GST SURF CITY 39.66N 74.17W
07/01/2021 M47 MPH OCEAN NJ MESONET
WEATHERFLOW.
0644 PM MARINE TSTM WIND 2 WNW SHIP BOTTOM 39.66N 74.21W
07/01/2021 M54 MPH ANZ451 NJ MESONET
WEATHERFLOW GAUGE XLBI.
0645 PM TSTM WND GST 1 NW SHIP BOTTOM 39.65N 74.19W
07/01/2021 M63 MPH ANZ451 NJ OTHER FEDERAL
0705 PM TSTM WND DMG 6 S BIG STONE BEACH 38.92N 75.31W
07/01/2021 SUSSEX DE TRAINED SPOTTER
DAMAGE TO SHINGLES AND SIDING OF SEVERAL
HOUSES. TIME ESTIMATED FROM RADAR.
1045 PM TSTM WND GST 1 NE KINGSTOWN 39.22N 76.04W
07/01/2021 M50 MPH QUEEN ANNE'S MD PUBLIC
MEASURED BY A TEMPEST WEATHER STATION NEAR
JUSTIN BUCH DR.
1050 PM TSTM WND DMG 1 W SUDLERSVILLE 39.19N 75.88W
07/01/2021 QUEEN ANNE'S MD 911 CALL CENTER
MULTIPLE TREES WERE REPORTED DOWN NEAR
SUDLERSVILLE. TIME ESTIMATED FROM RADAR.
1125 PM TSTM WND DMG HOPEWELL TWP. 39.44N 75.26W
07/01/2021 CUMBERLAND NJ 911 CALL CENTER
A COUPLE REPORTS OF DOWNED TREE LIMBS NEAR
HOPEWELL TWP. TIME ESTIMATED FROM RADAR.
1125 PM TSTM WND DMG 1 N HOPEWELL TWP. 39.45N 75.26W
07/01/2021 CUMBERLAND NJ 911 CALL CENTER
A COUPLE REPORTS OF DOWNED TREE LIMBS INTO
WIRES NEAR HOPEWELL TWP. TIME ESTIMATED FROM
RADAR.
0400 AM FLOOD 2 N HOPEWELL TWP. 39.47N 75.26W
07/02/2021 CUMBERLAND NJ OTHER FEDERAL
CONHANSEY RIVER AT SEELEY REACHED FLOOD
STAGE.
&&
$$
NOUS41 KPHI 030307 PNSPHI DEZ001>004-MDZ012-015-019-020-NJZ001-007>010-012>027-PAZ054-055- 060>062-070-071-101>106-031515- Public Information Statement National Weather Service Mount Holly NJ 1107 PM EDT Fri Jul 2 2021 ...NWS Damage Survey for July 1st 2021 confirms two Tornadoes... .Farmington DE to Houston DE Tornado... Rating: EF-1 Estimated Peak Wind: 90 mph Path Length /statute/: 3.9 miles Path Width /maximum/: 50 yards Fatalities: 0 Injuries: 0 Start Date: Jul 01 2021 Start Time: 4:52 PM EDT Start Location: 1 North of Farmington DE Start Lat/Lon: 38.8892 / -75.5826 End Date: Jul 01 2021 End Time: 4:55 PM EDT End Location: 1 SSW of Houston DE End Lat/Lon: 38.9032 / -75.5133 On Thursday afternoon, July 1st, 2021, a broken line of severe thunderstorms moved into Delaware from the Eastern Shore of Maryland. An embedded severe thunderstorm interacted with a sea breeze and remnant outflow boundary, generating a tornado that produced intermittent wind damage along a 3.9 mile path from Farmington to Houston, Delaware. Wind damage was first observed near a residence on Farmington Road, knocking down and snapping several trees in a narrow swath. The tornado then continued over railroad tracks and a cornfield, where a notable convergent pattern was observed. From there, the tornado proceeded eastward toward the South DuPont Highway, but not before causing damage to a business where metal roofing was peeled off. Several snapped trees were also noted on the property. Subsequently, the tornado crossed Gun and Rod Club Road where another area of trees were downed, with numerous branches across the roadway. South of Williamsville Road along Hogtown Road, a residence was damaged when a tree fell on to the roof. On the other side of the road, a corn field was present with a notable divergent pattern observed. This damage, south of the tornado track, was likely due to a RFD surge. The tornado then crossed a large wooded area with damage again observed to a property on the east side of the wooded area along Hunting Quarter Road. Numerous trees were snapped on the property with damage also occuring to a house due to a downed tree limb. Power lines were also knocked down. Debris was then lofted towards a farm across Hunting Quarter Road. The tornado then weakened and lifted just west of Deep Grass Lane with only a few down branches being noted. The National Weather Service thanks Kent County's Office of Emergency Management, the media, our SKYWARN spotters, and the public for their assistance in identifying damaged areas. .Milford DE to Slaughter Beach DE Tornado... Rating: EF-1 Estimated Peak Wind: 90 mph Path Length /statute/: 4.77 miles Path Width /maximum/: 100 yards Fatalities: 0 Injuries: 0 Start Date: Jul 01 2021 Start Time: 5:00 PM EDT Start Location: 2 ENE Milford DE Start Lat/Lon: 38.9209 / -75.3898 End Date: Jul 01 2021 End Time: 5:07 PM EDT End Location: Slaughter Beach End Lat/Lon: 38.9119 / -75.3031 On Thursday afternoon, July 1st, 2021, a broken line of severe thunderstorms moved into Delaware from the Eastern Shore of Maryland. An embedded severe thunderstorm interacted with a sea breeze and remnant outflow boundary, which generated the first tornado near Farmington, DE. The severe thunderstorm then produced another distinct tornado to the east along a 4.77 mile path from just east of Milford to Slaughter Beach, Delaware. Damage was first observed near residences at the Cedar Beach Road and McColley Road intersection. Here, several large branches and trees were snapped. Further east along Cedar Beach Road, more tree damage occurred across several residences with a couple of trees having been uprooted. The tornado then uplifted part of a porch roof to a residence on Shockley Road. Insulation that was underneath the roof was blown across Shockley Road and adhered to nearby homes. Insulation was also noted on all sides of the affected residence. At the intersection of Shockley and Cedar Neck Roads, a residence also had a large television antenna that was bent 180 degrees down towards the ground. Further east on Mills road, another residence observed multiple trees that were snapped. One large branch fell on an outdoor shed causing it to collapse, with other large branches falling on vehicles causing window damage. Towards Fannies Way, additional EF-1 damage was noted with a majority of roofing material lost to a pole barn along with two enclosed trailers being overturned. Roofing material from the pole barn along with tree branches were observed in the adjacent corn field. The tornado then moved eastward into marshland and proceeded towards the intersection of Bay Avenue and Slaughter Beach Road. Another pole barn lost a majority of roofing at the intersection with a small trailer having been overturned. Smaller tree branches were then snapped as the tornado lifted near the Delaware coastline. Interestingly, a nearby DEOS mesonet site measured a peak wind gust of 62 mph near this endpoint. The National Weather Service thanks Sussex County's Office of Emergency Management, the media, our SKYWARN spotters, and the public for their assistance in identifying damaged areas. && EF Scale: The Enhanced Fujita Scale classifies tornadoes into the following categories: EF0...Weak......65 to 85 mph EF1...Weak......86 to 110 mph EF2...Strong....111 to 135 mph EF3...Strong....136 to 165 mph EF4...Violent...166 to 200 mph EF5...Violent...>200 mph NOTE: The information in this statement is preliminary and subject to change pending final review of the events and publication in NWS Storm Data. $$ TD/ BAH
Notable Radar Imagery (GR2Analyst)
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| Figure 1: KDOX radar reflectivity factor (z; top left), storm relative velocity (SRM; top right), differential reflectivity (ZDR, bottom left) and correlation coefficient (CC; bottom right),) for the 0.5 degree elevation angle valid at 2054 UTC 1 July 2021. This was shortly after the touchdown of the Harrington, DE tornado. A classic QLCS tornado is evident, with the close proximity to the KDOX radar fortuitous in providing a detailed look at the storm. A debris ball/tornado debris signature is clearly evident in the enhanced reflectivity values, reduced ZDR values, and particularly the very low CC values. A tight velocity couplet is seen in the SRM data. | Figure 2: A vertical cross section of CC data for the KDOX radar during the same volume scan as in Figure 1. This methodology can be used to determine the approximate height to which tornadic debris is being lofted. A tilted vertical trail of reduced CC values is seen extending from the surface, representing lofted debris. In this case, the TDS is quite shallow, less than 5,000 feet, a value typical of relatively weak (EF0 or EF1) tornadoes. The relatively low maximum height of the data (<20,000 ft) and its sloped appearance is a side effect of close proximity to the KDOX radar. |
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| Figure 3: Same as Figure 1 valid at 2104 UTC 1 July 2021, about 10 minutes after the Harrington tornado. This time, the Milford to Slaughter Beach tornado is seen. The radar signature is in many ways similar to the first tornado. A tight velocity couplet is seen in the SRM, with a pronounced hook echo in the reflectivity. There is considerably more noise in the ZDR and CC data, but a tornado debris signature can still be seen where the dot has been placed. The vertical structure of the TDS (as in Figure 2, not shown) was very similar to the Harrington tornado, not surprising given the near equal intensities of the tornadoes. | Figure 4: KDOX radar reflectivity factor (left), and base velocity (V; right), for the 0.5 degree elevation angle valid at 2115 UTC 1 July 2021. The line of storms became outflow dominant as it approached the coast, bringing an end to the tornadic threat. However, as the outflow surged ahead, strong straight line winds continued. A 64 mph wind gust was measured near Lewes several minutes before rain arrived. The velocity data shows widespread 50 to 60 kt (about 60 to 70 mph) winds at 1000 ft or less above ground level. |
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| Figure 5: KDIX radar reflectivity factor (z; top left), storm relative velocity (SRM; top right), base velocity(V, bottom left) and correlation coefficient (CC; bottom right) for the 0.5 degree elevation angle valid at 2100 UTC 1 July 2021. In addition to the tornadoes in Delaware, an area of rotation over lower Bucks County, embdedded within a broader line of thunderstorms, prompted a Tornado Warning at nearly the same time. Rotation is clearly seen near Levittown, PA in the SRM data, and impressively high velocities in excess of 50 kt are seen in the V data. Tree and power line damage was reported in the area, but there did not appear to be evidence of a tornado touchdown. Rather, it is more likely a rear flank downdraft surge around the circulation, associated with the high base velocity values, caused the wind damage. There is a bit of noise in the CC data, but the mostly uniform high values offer no evidence of a TDS like those seen with the Delaware tornadoes. The broader thunderstorm line as a whole also produced a number of instances of wind damage over eastern PA. | Figure 6: Same as Figure 5 valid at 2135 UTC 1 July 2021. After weakening for a time, rotation redeveloped with the line segment from Figure 5. This time, the segment had reorganized to display some characteristics of a "bookend vortex". The increase in rotation prompted the issuance of an additional Tornado Warning. However, there was little in the way of damage reported with this feature, and no evidence that a tornado occurred. The rotation soon weakened, but this line did produce a couple of sporadic wind damage reports all the way to the coast. |
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