Eastern United States Severe and Tornado Event of 24 February 2016 by

Richard H. Grumm National Weather Service State College, PA 16803

1. Introduction

A strong low-level jet (Fig. 1) and deep moisture (Fig. 2) produce a massive winter severe weather event (Fig. 3) over the eastern United States on 24 February 2016. Over 360 severe weather reports were recorded on 24 February from South Carolina to Maine with at least 22 reported tornadoes. Rare February tornadoes were observed and verified in Lancaster and Bradford Counties in, Pennsylvania (red dots Figure 3). These were the first verified tornadoes in central Pennsylvania since 16 February 1990 and may have doubled the February tornado climatology for the state since 1900. However, the earliest published tornadoes were the Nashannock and Mercer; Tyrone, Greenbury, Tionesta and Huntingdon, PA tornadoes of 11 February 18871 (MWR 1887).

The storm reports on 24 February showed over 364 reports of severe weather and at least 22 tornadoes. Most of the tornadoes were in North Carolina and Virginia. The storm reports from 23 February showed over 140 reports with 45 tornadoes in the Gulf States, a more climatologically favorable location for late winter severe weather outbreaks. This raises the question as to why the second day of the outbreak so large so far north?

This note will examine the conditions of the rare northeastern United States winter severe weather and tornado event. Similar to many cold season severe and tornado events in the eastern United State, this was a quasi-linear convective system (QLCS) and the strong tornadic storms at times became nearly normal to the 0-3km shear which at times approached 60kts. The pattern is presented using the 00-hour analysis from GFS and the 3km HRRR. Where applicable, standardized anomalies are used to show the departures from normal. Radar data is focused on the severe weather signatures over Pennsylvania.

2. Methods and data

The NCEP GFS and HRRR were used to reconstruct the patterns and the standardized anomalies associated with the storm. A focus was on several key fields often used to anticipate the intensity of a storm.

Radar data and satellite data were recovered from AWIPS and saved in image formats only.

Severe weather reports and plots were from the Storm Prediction Center and region NWS office products.

3. Results a. The pattern

1 See the second page of this weather listing the third tornado listed under Tornadoes. Several of these tornadoes were listed as “very destructive”.

The large scale pattern (Fig. 4) showed an intense 500 hPa low moving into the eastern United States with deep southerly flow ahead of the progressive trough. The deep southerly flow produced a surge of deep warm moist air up the East Coast. The precipitable water (PW) values were in the 30 to 40mm range in the coastal plain during the afternoon and evening hours of 24 February 2016 (Fig. 5). The PW anomalies were 3 to 5σ above normal. The 850 hPa winds (Fig. 6) over 30ms-1 and were +3 to +4σ above normal. There were strong low-level winds and strong shear. Not shown, the 850 hPa temperatures too were above normal and the hourly HRRR data showed (Fig. 2) 850 hPa winds in excess of 40ms-1(80kts). Extremely strong low-level winds were present in the warm sector of the storm. These strong winds were oriented along with and maximized in the areas where the severe weather and tornadoes were observed.

On the cold side of this storm, heavy snow fell over portions of the Midwest from Michigan across northern Illinois.

It should be noted CAPE values in the GFS were relatively small and remained under about 400JKg-1 (not shown) and there was a strong 250 hPa jet which become more southerly as it moved up the East Coast (Fig. 7).

All the ingredients for heavy rain and severe weather were in place over the eastern United States with temperatures and moisture profiles in the warm sector more similar to May than February.

b. Radar and satellite

The GOES WV and IR shows (Fig. 8) the larger scale pattern over the East as the severe weather threat moved into the Mid-Atlantic region. The WV shows the dry slot and the plume of deep moisture to the east. The intrusion of mid-level dry air may have contributed to the instability above the boundary layer. The IR image shows deep convective cloud and the intense lightning along the north-south oriented line. At the time of the image there was lightning along the convective line from southern Virginia to north-central Pennsylvania.

From a radar perspective the intense north-south line was well organized from Maryland into central Pennsylvania by 2247 UTC (Fig. 9). Cores of 40 to 55 dBZ were present along the north south line. The cells on the line were moving rapidly to the north-northeast as the line slowly moved eastward. By 0004 UTC (Fig. 9 lower) the line had several strong elements, one in northern Maryland and two in central Pennsylvania. The element labeled L would develop a strong mesocyclone which produced wind damage as it moved across Lancaster County and later produced an EF2 tornado near Whitehorse, PA in Lancaster County. The approximate track of the Lancaster storm (L) is shown by the yellow arrow.

The Lancaster storm had extremely strong winds in it above about 3000ft likely due to the convection and the proximity of the 40 to 50 ms-1 LLJ (Fig. 2) which moved through the region. Radar winds from KLWX are shown here and values of base V often exceeded 100 to 110kts. KCCX, KDIX, and KLWX all showed a mesocyclone before the storm entered Lancaster County.

KLWX Z, V, and SRM are shown in Figures 10-13. These data show that outbound winds dominated the storm and the shear was so strong that the mesocyclone was visible in the V as well as SRM data. February or not, this storm had 60-70dBZ cores as it crossed Lancaster County. The images from 0016, 0020, 0022 and 0029 UTC are shown. The mesocyclone likely passed the region where the tornado was observed around 0029 UTC (Fig. 14).

The best view of the mesocyclone from KCCX is shown at 0019 UTC when the intensity peaked. The feature was defined by KCCX before it entered Lancaster County.

The NAM (Fig. 15) and RUC (Fig. 16) sounding near the time of the tornado showed strong low-level shear. The NAM sounding taken at a point over eastern Lancaster Co had around 60kts of shear in the 0-3km layer primarily from the south-southwest. The storm which surged along the line as it entered Lancaster County became nearly normal to the 0-3km shear. The sounding also showed the dry air above about 680 hPa which was indicated by the GOES-WV image. This drying may have acted as an elevated mixed layer.

Several other storms along the line farther north showed some interesting characteristics but are presently not shown.

4. Conclusions

A rare late winter severe weather event produced widespread severe weather from the Carolinas to New England on 24 February 2016. The strong frontal system produced over 22 tornadoes and basically tripled the official 1950-present recorded February tornado climatology for Pennsylvania from 1 to 3 tornadoes. This event produced the first known February EF2 tornado and the first tornados since February 1990. The 1887 tornadoes are not in the official climatology and warrant further investigation.

The tornadoes occurred in an environment which rarely develops in February. The surge of deep moisture and anomalous PW along with a strong low-level jet contributed to the instability and shear necessary for severe weather. The PW, 850 hPa winds, and temperatures were all well above normal for February. Surface temperatures were in the 50s and 60s over much of the mid-Atlantic region where the convection was observed and farther south temperatures were in the 70s. The CAPE was relatively low but the strong shear allowed for significant convection to develop.

The satellite and lightning data showed a line of storms which produced lightning from Pennsylvania to southern Virginia. The WV image implied a dry slot moving over the low-level moist air may have contributed to the event.

The radar data indicated an extremely strong mesocyclone with winds varying by over 80kts across the mesocyclone circulation which crossed Lancaster County, PA. The strong shear in the mesocyclone was detected by the 3 WSR-88D which cover Lancaster County. Base V in the area was observed to be over 100 to 110kts at times.

Strong winds, unseasonably warm and moist air came together to produce a rare February tornado event across Pennsylvania and the Mid-Atlantic region. This was a textbook example of a Quas-linear Convective System (QLCS: Schaumann and Przybylinski 2012). As in their study, isolated elements along the line became normal to the 0-3km wind shear. They noted that when the bulk 0-3km shear or greater than 15ms-1 (30kts) and a rear inflow jet (RIJ) or enhanced outflow caused a surge or bow the probability of a QLCS tornado dramatically increased. The Lancaster tornado occurred with 0-3km shear on the order of 30ms-1 (60kts), became more normal to the 0-3km shear as the cold pool developed and the system took on a bow-like shape. Only a few storms along the line came into balance in Pennsylvania on 24 February and the one which had the clearest signature and was nearly orthogonal to the 0-3km shear produced a tornado. Other storms to the south followed a similar evolution The Evergreen tornado in Appomattox County, VA had a similar evolution (Blacksburgh storm survey report). This 17 mile long tornado produced EF3 damage.

The extent of the reported tornado event of 11 February 1997 implies that a line of severe storms, a QLCS, crossed the State on 11 February 1887 and may have produced the first reported February Pennsylvania tornado outbreak with at least 5 potential tornadoes. The 11 February 1887 event apparently produced 18 potential tornadoes from Sheblyville, Indiana (1 tornado: 4 AM), across Ohio (8), Kentucky (1), Pennsylvania (5), New York (2),and New Midway, Maryland (1: 15 PM).

5. Acknowledgement

Lancaster EMA for storm damage data and information to include locations of significant damage. Elyse Hagner for research on February tornadoes and tornado climatologies.

6. References

Monthly Weather Review, February 1987: pages 48-49 on line in PDF format.

Figure 1. NCEP 3km HRRR analysis of the 850 hPa winds (ms-1) in hourly increments from a) 2200 UTC 24 February through f) 0300 UTC 25 February 2016. Return to text.

Figure 2. As in Figure 1 except for HRRR precipitalbe water and anomalies. Return text.

Figure 3. Storm Prediction Center storm reports for 24 and 23 February 2016. Return to text.

Figure 4. NCEP GFS 00-hour forecasts of 500 hPa heights and height anomalies in 12 hour increments from a) 0000 UTC 23 to f) 1200 UTC 25 February 2016. Return to text.

Figure 5. As in Figure 4 except for precipitable water every 6 hours from a) 0000 UTC 24 February through f) 0600 UTC 25 February 2016. Return to text.

Figure 6. As in Figure 5 except for 850 hPa winds and v-wind anomalies. Return to text.

Figure 7. As in Figure 6 except for 250 hPa wind shaded above 20ms-1. Return to text.

Figure 8. GOES WV at 0037 UTC and IR at 2300 UTC 24 and 25 February respectively. Return to text.

Figure 9. KCCX radar of base Z at 2347 24 February and 0004 UTC 25 February 2016. Labels show significant returns or features tracked on radar. The L is the storm which moved across Lancaster County, The yellow arrow shows where this storm tracked. Return to text.

L

B

C

Figure 10. KLWX radar at 0016 UTC showing clockwise from top Z, V, SRM and Z. Return to text.

Figure 11. As in Figure 10 except valid at 0020 UTC. Return to text.

Figure 12. As in Figure 10 except valid at 0022 UTC. Return to text.

Figure 13. As in Figure 10 except valid at 0029 UTC. Blue line tracks mesocyclone and ends near location of EF2 tornado north of Gap, AP. Return to text.

Figure 14. As in Figure 10 except for KCCX valid at 0019 UTC. Lower left has KDP. Return to text.

Figure 15. NAM sounding at a point in eastern Lancaster County at 0000 UTC 25 February 2016. Return to text.

Figure 16. As in Figure 15 but RAP sounding at 2300 UTC. Note dry layer is higher than in NAM. Return to text.

Figure image from Blacksburgh storm survey report. Provided by WFO Blacksburgh, VA

493 NOUS41 KCTP 261904 PNSCTP PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046- 049>053-056>059-063>066-262315- PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE STATE COLLEGE PA 204 PM EST FRI FEB 26 2016 ...EF2 TORNADO CONFIRMED IN LANCASTER COUNTY... LOCATION...WHITE HORSE IN LANCASTER COUNTY PENNSYLVANIA DATE...FEBRUARY 24 2016 ESTIMATED TIME...0738 PM EST MAXIMUM EF-SCALE RATING...EF2 ESTIMATED MAXIMUM WIND SPEED...120-125 MPH MAXIMUM PATH WIDTH...400 YARDS PATH LENGTH...4.87 MILES BEGINNING LAT/LON...40.01N / 76.03W ENDING LAT/LON...40.07N / 75.98W * FATALITIES...0 * INJURIES...0 * THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO CHANGE PENDING FINAL REVIEW OF THE EVENT(S) AND PUBLICATION IN NWS STORM DATA. ...SUMMARY... THE NATIONAL WEATHER SERVICE IN STATE COLLEGE PA HAS CONFIRMED AN EF2 TORNADO NEAR WHITE HORSE IN LANCASTER COUNTY PENNSYLVANIA ON FEBRUARY 24 2016. THE TORNADO TOUCHED DOWN ONE-HALF MILE SOUTHWEST OF THE INTERSECTION OF AMISH ROAD AND SPRING GARDEN ROAD THEN TRAVELED TO THE NORTHEAST AT A SPEED OF AROUND 50 MPH...STAYING ON THE GROUND FOR 7 MINUTES. AN ESTIMATED 50 BUILDINGS SUSTAINED DAMAGE ALONG THE PATH OF THE TORNADO. TWO LARGE FARM OUTBUILDINGS AND ONE TWO- STORY RESIDENCE HAD THE MAJORITY...OR THEIR ENTIRE ROOFS BLOWN OFF NEAR THE INTERSECTION OF AMISH ROAD AND SPRING GARDEN ROAD. THIS MARKED THE TRANSITION OF THE TORNADO FROM EF1 TO EF2. A VAN WITH SEVERAL PASSENGERS TRAVELING WEST ON SPRING GARDEN ROAD AND NEAR THE SAME INTERSECTION WAS BLOWN ABOUT 10 FEET TO THE NORTH OF THE ROAD AND INTO A FIELD. AROUND ONE HALF MILE TO THE NORTHEAST AND ALONG MILLWOOD ROAD...ADDITIONAL EF2 DAMAGE OCCURRED AS ROOFS WERE BLOWN OFF SEVERAL FARM OUTBUILDINGS AND BARNS... ALONG WITH ONE TWO STORY RESIDENCE. A PINE TREE LOCATED IN THE FRONT YARD WAS STRIPPED OF MOST OF ITS BRANCHES AND FOLIAGE...WITH ONLY A FEW LARGER BARE LIMBS REMAINING. A WOODEN BARN BEHIND THE RESIDENCE WAS COMPLETELY DESTROYED WITH SUBSTANTIAL DEBRIS CARRIED SEVERAL HUNDRED YARDS TO THE NORTHEAST ACROSS A FIELD. MID TO HIGH END EF1 DAMAGE TO ROOFS WAS NOTED TO SEVERAL FARM BUILDINGS AND HOMES ALONG THE EAST-WEST PORTION OF MILLWOOD ROAD...AND ALONG OLD PHILADELPHIA PIKE NEAR SCHOOL LANE ROAD. A SIGNIFICANT AMOUNT OF DEBRIS IN THE FORM OF CRUMPLED SHEET METAL FROM ROOFS WAS SCATTERED ACROSS FIELDS ADJACENT TO MEETING HOUSE ROAD TO THE NORTH OF OLD PHILADELPHIA PIKE. A SECOND AREA OF CONCENTRATED EF2 DAMAGE WAS NOTED NEAR THE INTERSECTION OF SELDOMRIDGE ROAD AND CAMBRIDGE ROAD. THE TORNADO KNOCKED OVER SEVERAL LARGE GRANITE TOMBSTONES IN A CEMETERY...THEN STRIPPED ABOUT ONE QUARTER OF THE ROOF OFF A LARGE BUILDING WHERE MORE THAN 100 PEOPLE WERE ATTENDING AN AUCTION. THE FINAL LOCATION OF EF2 DAMAGE WAS NOTED ALONG KAUFFROTH ROAD AND JUST A FEW HUNDRED YARDS TO THE NORTH OF

ITS INTERSECTION WITH SELDOMRIDGE ROAD. IT WAS HERE WHERE A LARGE ONE- ROOM METAL AMISH SCHOOL WAS COMPLETELY DESTROYED AND BLOWN ABOUT 100 YARDS UPHILL AND INTO A FIELD. THE TORNADO BEGAN TO WEAKEN FROM THIS POINT WITH THE FINAL EF1 DAMAGE NOTED NEAR THE INTERSECTION OF GAULT ROAD AND ROSEHILL DRIVE WHERE SIGNIFICANT DAMAGE OCCURRED TO ROOFS AND SIDING ON SEVERAL HOMES AND SHEDS. SEVERAL SOFTWOOD TREES WERE ALSO UPROOTED AT THE END OF THE TORNADO PATH ABOUT 100 YARDS TO THE NORTH OF THISTLE DRIVE. THIS INFORMATION CAN ALSO BE FOUND ON OUR WEBSITE AT WEATHER.GOV/STATECOLLEGE. FOR REFERENCE...THE ENHANCED FUJITA SCALE CLASSIFIES TORNADOES INTO THE FOLLOWING CATEGORIES: EF0...WIND SPEEDS 65 TO 85 MPH. EF1...WIND SPEEDS 86 TO 110 MPH. EF2...WIND SPEEDS 111 TO 135 MPH. EF3...WIND SPEEDS 136 TO 165 MPH. EF4...WIND SPEEDS 166 TO 200 MPH. EF5...WIND SPEEDS GREATER THAN 200 MPH. $$ HAGNER/LAMBERT/WATSON/CHABALA