Impact of hurricane Katrina on central Pennsylvania: Tornadoes and rain

By Richard H. Grumm, Michael Dangelo,

And Ron Holmes

National Weather Service Office State College, PA 16803

1. INTRODUCTION Hurricane Katrina had a severe impact on the Gulf Coast of the United States. This storm produced damage of historic and catastrophic proportions in Louisiana, Mississippi, and Alabama. A this time, hurricane Katrina was the third most intense hurricane to hit the United States since 1851, according to the National Weather Service data on tropical storms and hurricanes. The "Labor Day Hurricane" of September 1935, which struck the Florida Keys and hurricane Camille in 1969 were more intense. The storm was more intense than hurricane Andrew when it struck the east coast of Florida in August, 1992. The winds with Katrina were estimated to be as high as 140 mph at landfall. These values may likely rise as survey’s of the storm are completed. At the current time, this storm ranks as a strong Category 4 hurricane on the Saffir-Simpson scale of hurricane intensity. These strong winds and flood waters created wave action on Lake Pontchartrain, this led to a breach in the levy’s, flooding most of the city of New Orleans on Tuesday and Wednesday 30-31 August 2005. The impact of the remnants of hurricane Katrina were minimal in Pennsylvania and inconsequential relative to the catastrophic impacts of the storm on the

Gulf Coast. However, the storm did produce heavy rains in northern and western Pennsylvania on the 30th and early on the 31st. One feeder band produced a persistent thunderstorm which produced at least 2 confirmed tornado touchdowns. This paper will serve to document the impacts of remnants of hurricane Katrina on central Pennsylvania. The focus will be on the tornadic activity and storm damage in the Keystone State. Due to the catastrophic nature of the storm, some SREF and observed data are presented to provide an overview of the scope of the storm after it made landfall on the United States. The SREF data provided useful guidance associated with all aspects of this storm. 2. METHODS All meteorological data were collected in real-time. These data include radar, satellite, and model data. Most of these data were archived and displayed using AWIPS. GrADS was used to display model data relative to the climatic normals. Storm pictures and maps are based on surveys conducted by National Weather Service Office employee’s in conjunction with local emergency management personnel.

Figure 1 Visual satellite image valid at 1400 UTC 29 August 2005 with 1400 UTC surface and bouy observations. Image has been cropped to focus over the area of interest.

3. RESULTS i. Overview of Katrina Figure 1 shows a visual image of hurricane Katrina at 1400 UTC 29 August 2005, shortly after making landfall along the Gulf coast of Louisiana and western Mississippi. The eye of the storm can be seen over the Bay east of lake Pontchartrain. The surface observations show the large cycloninc circulation encompassing the storm with clouds and rain well north of the main center of the storm. The high dew point air has extended well north of the storm suggesting a surge of warm moist tropical air over much of the eastern United States. Ensemble forecasts showed that the storm was forecast to move northward. The forecast track suggested

Pennsylvania would remain on the east side of the storm, a location where feeder bands and warm-moist tropical air could surge into the region. The forecasts called for heavy rains over northern and western parts of the State with bands of showers and the threat of tornadoes in these bands late Tuesday (30 August) and early Wednesday (31 August. Short-term ensemble data will be used to illustrate these forecasts. ii. Ensemble forecasts Figure 2 shows the 0900 UTC 28 August 2005 SREF MSLP forecasts valid at 1200 UTC 29 August 2005, around the anticipated time of landfall along the Gulf coast. A landfall near Louisiana was in earlier forecasts and is not shown. These data suggest an extremely anomalous cyclone would cross the coastal areas of Louisiana early on

Figure 2 SREF initialized at 0900 UTC 28 August 2005 showing MSLP forecasts valid at 1200 UTC 29 August 2005. Upper panel shows spaghetti plots and spread. Lower panels shows the ensemble mean and the departure of the mean in standard deviations from normal.

Monday morning. The low pressure anomalies were off the normal scale as is the case with extreme low pressures in low and tropical latitudes. By 0000 UTC 31 August the SREFs had the surface cyclone center over Tennessee (not shown) with the ensemble mean pressure to be -4.98 standard deviations below normal. The SREFs also showed a high probability of heavy rains and significantly above normal winds at 850 hPa.

Figure 3 shows the MSLP forecasts initialized 12 hours later, at 0900 UTC 29 August 2005. These forecasts show Katrina making landfall about this time over southeastern Louisiana. The ensemble mean 850 hPa winds (Figure 4) were forecast to be much above normal north of the cyclone center (upper panel) with equally as strong and anomalous southerly winds on the east side of the cyclone. Typically, heavy rains are observed in the anomalous easterly flow and showers, thunderstorms, and tornaodoes are dominant in the southerly wind anomalies as tropical storms under-go extratropical transitions. Figure 5 shows the 850 hPa winds and anomalies valid at 0300 UTC 31 August 2005. The 850 hPa cyclone was forecast to be over northern Kentucky. The strong easterly jet and potential heavy rainfall area was forecast to be over Indiana and Ohio. The anomalous southerly jet was forecast to be over the Ohio

Valley. These forecasts proved to be too slow in advancing the surface cyclone, but were representative of the conditions and captured the major potential weather threats in the correct general regions. Figure 6 shows the 850 hPa wind forecasts initialized at 0900 UTC 30 August 2005 valid at 0300 UTC 31 August 2005. In these forecasts, the 850 hPa low was over southern Indiana, slightly north of the SREF forecasts

initialized 24 hours earlier. The strong easterly jet was still over Ohio and Indiana with a strong southerly jet over West Virginia and points east. The easterly jet defined the general area of observed and forecast heavy rains (Figure 7) and the low-level southerly jet was associated with the area of severe weather (Figure 6 lower panel). The SREFs showed the highest probability of 2 inches or more rainfall over Ohio, northwestern Pennsylvania and western New York. Previous SREF forecasts showed slightly more rainfall (QPF) in the same general areas (not shown). iii. Impacts on Pennsylvania The impacts of the remnants of hurricane Katrina were primarily in the form of locally heavy rains in the northern and western portions of the State (Figure 8) and tornadoes in south-central portions of the State. Rainfall amounts of 2-4 inches were observed in the northwest. Objectively analyzed rainfall data for the two days of rainfall (Figure 9) show that the data in Figure 8 were representative of what was likely observed. However,

antecedent dry to drought-like conditions precluded any serious or widespread flooding. The white arrow in Figure 8b shows the band of rain that mnorthward across south-central Pennsylvania. The strongesin this band was near the Pennsylvania border at 0400 UTC31 August as shown in Figure 8a Interestingly, where this storm produced the highest rainfallestimates was also the location observed tornado damage.

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Figure 3 SREF initialized 0900 UTC 29 August 2005 showing ensemble mean and departures from normal valid at 1200 UTC 29 August 2005.

College conducted 2 storm surveys on 31 August and 2 storm surveys on 1 September 2005. The first survey wasconducted in Cumberland County and covered northern York County as showin Figure 10. In this area, an F1 tornado touchdown near Creek road around 115 AM, about 1 mile south of Yellow Breeches creek and moved northwasnapped and uprooted trees and caused minor damage to two homes in York County.

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Ta park along the creek felling and uprooting trees. Exiting the part aloRosegarden Drive, the tornado went upthe street uprooting and topping trees. Atopped tree damaged the east side of one home penetrating the wall and front door. The tornado then sucked the tretop out of the house damaging the SUV’s in the drive way. Most housthe west side of the street were struck by debris from all for compass directions. On the east side of the street, damage appeared to converge toward the street

The tornado continued northeastward (040 degrees) affecting more of the neighborhood doing mainly minor damage to roof shingles, siding andsoffit. The tornado crossed West Lisbroad and went down Stumpstown road. Several trees were uprooted along Stumpstown road and minor damage to homes was observed along Stumpstown road. A seco

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nd survey was conducted in a more rural area of Adams County from

northeast of Gettysburg to near Heidlersburg (Figure 11). The Ftornado in this region generally paralleled US-15. Trees were doof the intersection of US-30 and US-15. After crossing US-15 the storm destroyed several old out buildinfarm. Sporadic damage was sight as the storm moved toward the northeast (about040) a farm (red arrow) along Swift Run Road (RT-394) a farm near two ponds sustained uprooted trees and minor damage to the house. An old outbuilwas destroyed.

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Tinto the cornfield as it continued northeastward. From the ground osporadic damage could be found tracinroads nearest the path. The most damage was found on Millar road (black arrow Figure 11). Due to the roads shape, the

rossed the road twice. At the first crossing it produced light damage one home, snapped two power poles, destroyed a shed, de-roofed two barnsand moved a hay wagon across the roadSuction vortex-like swirls were present in the grass and cornfields. Trees, were present were snapped or uprooted.

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Athe tornado ripped up power poles, demolished an old barn, and did minor

damage to a house. Trees in the area hadsnapped and twisted limbs. Debris from the barn, mainly tin roofing was in the trees, wrapped around poles and strewnin a path about 0.5 mile northeastward into a field. Some of the debris was found 1 mile to the northeast along R234 in Hiedlersburg. (the thick black road where the known track terminate Mthis location. Photographic evidence in near the Maryland and Pennsylvania border showed similar damage suggesting F1 like damage just wRT-15. If this is confirmed as tornado damage, the storm that produced this tornado had a skipping tornado of lengon the order of 10-20 miles. Asurveyed on 1 September near Bain northeast Lycoming County. This tornado occurred around 453 AM EDon 31 August 2005. v Ttornado(es) and the band of locaheavy rain was well sampled by the KCCX and KLWX WSR-88D radarsThe storm was monitored while it was still in Maryland with severe thunderstorm warnings issuedapproached Pennsylvania followed within 5 minutes by a tornado warniRadar based tornado warnings were issued in all three affected counties. F shows the rotating thundersto d 0438 rm at 0405 UTC anUTC 31 August 2005 as viewed from the Sterling, Virginia (KLWX) WSR-88D. The white arrow shows the mesocyclone at 0405 and the

Figure 4 As in Figure 4 except SREF 850 hPa winds valid showing a) winds and U-wind anomalies and b) winds and V-wind anomalies.

approximate region of the F1 dsouthern Adams County. The white line shows the general path of the storm, which produced at least 2 known torntouch downs along the path. The 0434 UTC image shows the storm and mesocyclone northeast of Gettysbthe storm moved across the region shown in the survey map in

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igure 13 F shows the storm as viewed

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from the KCCX radar as it moved intoCumberland County (0504 UTC) and asthe storm moved northward into the Harrisburg area (0536 UTC). These dshow that the storm maintain rotation across a considerable portion of

Cumberland County, though tornado and wind damage waslimited to a small area as outlined in Figure 10. 4. CONCLUSIONS

urricane Katrina came ashore

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Halong the Gulf Coast during the morning hours of 29 August 200This storm will likely be one of the largest “natural” disasters to strike the United States during th21st century. The damage and death toll will likely be very laexceeding those associated with any recent hurricane. Inthis historic storm brought heavy rains to northern and western portions of the State. Antecededry to drought-like conditions precluded any significant floodin the State. The rains in the northwest are quite common association with tropical storms as they interact with a mid-latitudinal

frontal system. Mainly east-west bawere observed in Ohio and Pennsylvaniawhere the heavy rains fell. These bands were in close proximity to the intense low-level easterly jet. Fwith southeasterly flow produced narrowfeeder bands. These bands often produce severe weather and tornadoes. The remnants of hurricane Ivan in Septe2005 and hurricane Fran in September 1996 produce tornadoes in these low-topped tropical feeder bands. Similar tthese previous events, the remnants of tropical hurricane Katrina produced tornadoes in the generally south to no

Figure 5. As in Figure 5 but for forecasts valid at 0300 UTC 31 August 2005.

oriented feeder bands which developed in the tropical air. Both the KCCX and KLWX radar

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y rains and tornadoes ith recent tropical storms suggest a

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5. ACKNOWLEDGEMENTS

g the ath and intensity of hurricane Katrina at

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captured the thunderstorm and low-circulations in the thunderstorms that produced all known damage in the threaffected counties. Tforecasting the intensity and landfall ohurricane Katrina. Over Pennsylvania, the dual threat of heavy rains in the northwest and severe weather in the southeast were well represented in th

The areas of heavwuseful forecast conceptual model associated with these systems. These include:

• H

and west of the cyclone track. This area is located in the low-level cool air of a general east-west baroclinic zone. Bands of showers and thunderstorms in the msoutherly flow regime aRotating storms in this bandproduce tornadoes. Elevated convection where the tropical flow movescooler air. Interaction may produce enhanced convection and thunderstorms in these regions, which lie east of the tropical cyclone center. Antecedent conditions play a significant role in flood pDespite rainfall amounts similto those produce by tropical storm in 2004, no significant flooding was observed due toantecedent low flows in riversand dry soils.

To all those involved in forecastinpthe National Hurricane Center in Coral Gables, Florida. Their incredible efforts likely saved tens of thousands of lives. The members and families of the National Weather Service Office in Slidell Louisiana who weathered tstorm and provided warnings to the people of New Orleans as they too fac

devastation. To the local EmergencyManagement office in Cumberland and Adam’s County Pennsylvania for facilitating timely and efficient storm surveys. Finally, to the forecast offState College for timely warnings and efforts to verify and learn from this event. 6. RE

Figure 6 As in Figure 5 except SREF 850 hPa winds and anomalies initialized at 0900 UTC 30 August 2005 valid at 0300 UTC 31 August 2005.

ice in

FERENCES one at this time.N

Figure 7 SREF forecasts of 2.00 incher or more precipitation for the 36-hour period ending at 0000 UTC 01 September 2005 from forecasts initialized at 0900 UTC 30 August 2005. Upper panels shows probability of 2.00 inches or greater lower panel shows the ensemble mean and each members 2.0 inch contour.

Figure 8 Base reflectivity valid at 0400 UTC 31 August 2004 and b) storm total precipitation from KCCX with 24-hour rainfall observations in white. STP product time ends at 1300 UTC 31 August 2005. Return to text.

Figure 9 Two total rainfall observed from the cooperative precipitation network. Data are in inches and are the 48-hour totals valid ending at 1200 UTC 1 September 2005. Return to text.

Figure 10 Approximate path (blue) of F1 tornado in southern Cumberland and northern York Counties. Eyewitness accounts put the tornado time in AshCombe Farms development (black arrow) at 0120 AM EDST. The county line (brown) is Yellow Breeches Creek. Return to text.

Figure 11. Storm survey of northern Adams County F1 tornado. Black ashows Millar Road and red arrow the farm.

rrow to text.Return

Figure 12. KLWX base reflectivity and storm relative winds (SRM) valid at (upper) 0405 UTC 31 August 2005 and (lower) 0438 UTC 31 August 2005. White arrow shows mesocyclone and white line shows the approximate path of the storm and tornado paths. Return to text.

Figure 13 As in Figure 12 except for KCCX radar valid at (upper) 0504 UTC and (lower) 0536 UTC 31 August 2005. Return to text.