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NOAA TM NWS ER-52

NOAA Technical Memorandum NWS ER-52

U.S. DEPARTMENT OF COMMERCE F National Oceanic and Atmospheric Administration National Weather Service

FORECAST AND WARNING UTILIZATION OF RADAR REMOTE FACSIMILE DATA

Robert E. Hamilton

Eastern Region Garden City,NY

July 1973 NOAA TECHNICAL MEMORANDA National Heather Service, Eastern Region Subseries

The National Heather Service Eastern Region (ER) Subseries provides an informal medium for the documentation and quick dissemination of results not appro­ priate, or not yet ready, for formal publication. The series is used to report on work 1n progress, to describe technical procedures and practices, or to relate progress to a limited audience. These Technical Memoranda will report on investigations devoted primarily to regional and local problems of Interest mainly to ER personnel, and hence will not be widely distributed.

Papers 1 to 22 are in the former series, ESSA Technical Memoranda, Eastern Region Technical Memoranda (ERTM); papers 23 to 37 are in the former series, ESSA Technical Memoranda, Heather Bureau Technical Memoranda (HBTM). Beginning with 38, the papers are now part of the series, NOAA Technical Memoranda NWS.

Papers 1 to 22 are available from the National Heather Service Eastern Region, Scientific Services Division, 585 Stewart Avenue, Garden City, N.Y. 11530. Beginning with 23, the papers are available from the National Technical Information Service, U.S. Department of Cownerce, Sills Bldg., 5285 Port Royal Road, Springfield, Va. 22151. Price: $3.00 paper copy; $0.95 microfilm. Order by accession number shown in parentheses at end of each entry.

ESSA Technical Memoranda ERTM 1 Local Uses of Vort1c1ty Prognoses 1n Heather Prediction. Carlos R. Dunn. April 1965

ERTM 2 Application of the Barotroplc Vorticity Prognostic Field to the Surface Forecast Problem. Silvio G. Simplicio. July 1965

ERTM 3 A Technique for Deriving an Objective Precipitation Forecast Scheme for Columbus, Ohio. Robert Kuessner. September 1965

ERTM 4 Stepwise Procedures for Developing Objective Aids for Forecasting the Probability of Precipitation. Carlos R. Dunn. November 1965

ERTM 5 A Comparative Verification of 300 mb. Winds and Temperatures Based on NMC Computer Products Before and After Manual Processing. Silvio G. Simplicio. March 1966

ERTM 6 Evaluation of 0FDEV Technical Note No. 17. Richard M. DeAngelis. March 1966

ERTM 7 Verification of Probability Forecasts at Hartford, Connecticut, for the Period 1963-1965. Robert B. Wassail. March 1966

ERTM 8 Forest-F1re Pollution Episode 1n West Virginia November 8-12, 1964. Robert 0. Weedfall. April 1966

ERTM 9 The Utilization of Radar in Meso-Scale Synoptic Analysis and Forecasting. Jerry D. Hill. March 1966

ERTM 10 Preliminary Evaluation of Probability of Precipitation Experiment. Carlos R. Dunn. May 1966

ERTM 11 Final Report. A Comparative Verification of 300 mb. Hinds and Temperatures Based on NMC Computer Products Before and After Manual Processing. Silvio G. Simplicio. May 1966

ERTM 12 Summary of Scientific Services Division Development Work in Sub-Synoptic Scale Analysis and Prediction - Fiscal Year 1966. Fred L. Zuckerberg. July 1966

ERTM 13 A Survey of the Role of Non-Adiabatlc Heating and Cooling in Relation to the Development of Mid-Latitude Synoptic Systems. Constantine Zo1s. July 1966

ERTM 14 The Forecasting of Extratroplcal Onshore Gales at the Virginia Capes. Glen V. Sachse. August 1966

ERTM 15 Solar Radiation and Clover Temperature. Alex J. Kish. September 1966

ERTM 16 The Effects of Dams, Reservoirs and Levees on River Forecasting. Richard M. Greening. September 1966

ERTM 17 Use of Reflectivity Measurements and Reflectivity Profiles for Determining Severe Storms. Robert E. Hamilton. October 1966

ERTM 18 Procedure for Developing a Nomograph for Use in Forecasting Phenological Events from Growing Degree Days. John C. Purvis and Milton Brown. December 1966

ERTM 19 Snowfall Statistics for Williamsport, Pa. Jack Hummel. January 1967

ERTM 20 Forecasting Maturity Date of Snap Beans in South Carolina. Alex J. Kish. March 1967

ERTM 21 New England Coastal Fog. Richard Fay. April 1967

ERTM 22 Rainfall Probability at Five Stations Near Pickens, South Carolina,1957-1963. John C. Purvis. April 1967

WBTM ER 23 A Study of the Effect of Sea Surface Temperature on the Areal Distribution of Radar Detected Precipitation Over the South Carolina Coastal Waters. Edward Paquet. June 1967 (PB-180-612)

WBTM ER 24 An Example of Radar as a Tool 1n Forecasting Tidal Flooding. Edward P. Johnson. August 1967 (PB-180-613)

WBTM ER 25 Average Mixing Depths and Transport Wind Speeds over Eastern United States in 1965. Marvin E. Miller. August 1967 (PB-180-614)

WBTM ER 26 The Sleet Bright Band. Donald Marier. October 1967 (PB-180-615)

WBTM ER 27 A Study of Areas of Maximum Echo Tops 1n the Washington, D.C. Area During the Spring and Fall Months. Marie D. Fellechner. April 1968 (PB-179-339)

WBTM ER 28 Washington Metropolitan Area Precipitation and Temperature Patterns. C. A. Woollum and N. L. Canfield. June 1968 (PB-179-340)

WBTM ER 29 Climatological Regime of Rainfall Associated with Hurricanes after Landfall. Robert W. Schoner. June 1968 (PB-179-341)

WBTM ER 30 Monthly Precipitation - Amount Probabilities for Selected Stations in Virginia. M. H. Bailey. June 1968 (PB-179-342)

WBTM ER 31 A Study of the Areal Distribution of Radar Detected Precipitation at Charleston, S. C. S. K. Parrish and M. A. Lopez. October 1968 (PB-180-48CJ

WBTM ER 32 The Meteorological and Hydrological Aspects of the May 1968 New Jersey Floods. Albert S. Kachic and William Long. February 1969 (Revised July 1970) (PB-194-222)

WBTM ER 33 A Climatology of Weather that Affects Prescribed Burning Operations at Columbia, South Carolina. S. E. Wasserman and J. D. Kanupp. December 1968 \tUn- /I —UUIjt/ WBTM ER 34 A Review of Use of Radar in Detection of Tornadoes and Hail. R. E. Hamilton. December 1969 (PB-188-315)

WBTM ER 35 Objective Forecasts of Precipitation Using PE Model Output. Stanley E. Wasserman. July 1970 (PB-193-378)

WBTM ER 36 Summary of Radar Echoes in 1967 Near Buffalo, N.Y. Richard K. Sheffield. September 1970 (C0M-71-00310)

WBTM ER 37 Objective Mesoscale Temperature Forecasts. Joseph P. Sobel, September 1970 (C0M-71-0074) nqaa Tg<;hni<;ai Memoranda NWS

NWS ER 38 Use of Primitive Equation Model Output to Forecast Winter Precipitation in the Northeast Coastal Sections of the United States. Stanley E. Wasserman and Harvey Rosenblum. December 1970 (C0M-71-00138) 7

NWS ER 39 A Preliminary Climatology of A1r Quality in Ohio. Marvin E. Miller. January 1971 (COM-71-00204)

(Continued On Inside Rear Cover) /f QC

UNITED STATES DEPARTMENT OF COMMERCE "Hi/., sz NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION c.z NATIONAL WEATHER SERVICE EASTERN REGION Garden City, New York

NOAA TECHNICAL MEMORANDUM NWS ER-52

FORECAST AND WARNING UTILIZATION OF RADAR REMOTE FACSIMILE DATA

ROBERT E. JHAM1LT0N PnA.ncA.pal Ki>i>ii>tanl National Weathen SeAvT.ce. Eoneca&t O^lce Cleveland., Ohio

ATMOSPHERIC SCIENCE.^ LIBRARY . _ j SEP 06 1973

N.O.A.A. U. S. Dept, of Commerce SCIENTIFIC SERVICES DIVISION Eastern Region Headquarters July 1973

73 5334 FORECAST AND WARNING UTILIZATION OF RADAR REMOTE FACSIMILE DATA

INTRODUCTION

This paper illustrates the relationship of radar patterns received via Weather Bureau Radar Remote (WBRR) to significant weather phenomena. The emphasis is on severe local storms. The cases presented can serve as a training manual nucleus to which additional cases should be added in the future. In some of the cases to be discussed warnings were issued for either severe thunderstorms or tornadoes, based on the echo top or intensity data obtained from a WSR-57 radar station. In most cases warnings were based on echo configuration, movement, and intensity taken solely from a WBRR-68 display distant from the WSR-57 location. One distinct advantage the facsimile product provides is a record of the echo data. A forecaster with facsimile copy can evaluate echo configuration and changes in the pattern. He can determine detailed echo movement and intensity and note short or long- period changes.

In severe weather situations radar is one of the most important tools available to the forecaster. In order to accurately evaluate radar patterns, the forecaster must be familiar with not only the macro-scale weather patterns, but also meso- and micro-scale developments. All forecasters should remember, however, that small-scale systems and pressure patterns are frequently very different from the macro-scale patterns and can move in directions and with speed quite different from what would be indicated by the large-scale patterns. The six cases to be discussed all occurred in Ohio in 1972 where during this period most tornadoes were associated with small-scale weather patterns. The tornadoes usually touched the surface for short distances and several were described as tree-top tornadoes inflicting most of their damage to trees, power lines, and tops of buildings. These storms frequently struck from the northwest.

An interesting radar feature that occurred in four of the cases to be described was the Line Echo Wave Pattern (LEWP). This pattern has been associated with severe weather by Nolen 1959, Pautz and Doloresco 1963, and several other authors. The LEWP can be described as a raeso-wave pattern in a line of echoes with part of the line having been subjected to an acceleration. A high percentage of 1972 Ohio tornadoes were associated with the meso-LEWPS. This raises the question, "Should we issue tornado warnings downstream from a well defined LEWP or meso-LEWP?" Perhaps the answer is yes, at least in Ohio and for LEWPS with echo tops 2 near or above the tropopause and/or for system movements in excess of surrounding echo movements. The important statistic that is not presently known is how many LEWPS occurred without tornadoes or even severe thunderstorms. Until this is known,a definite recommendation can not be made.

For all cases that follow, the location of the WSR-57 is Detroit and the location of the WBRR is the Weather Service Forecast Office at Cleveland. The range markers on the WBRR pictures are for 25-mile intervals from Detroit. The intensity of echoes are determined through use of a Video Integrator and Processor (VIP). The weakest intensity (VIP level 1) is shown on WBRR pictures and in the illustrations as grey; the next higher echo intensity (VIP level 2) is shown as black. A white area (inside the black) depicts still higher intensity echoes (VIP level 3). This order of shading is repeated once again inside the white area for increasingly greater echo intensity (VIP levels 4 through 6). - 3 -

CASE 1

RADAR PATTERN ASSOCIATED WITH AN UPPER VORTEX OR SHEAR AREA

Occasionally you can identify an upper vortex or closed Low from the radar echo configuration. The pattern is distinguishable by its comma shape, with the center of the circulation at the eye of the comma (Figure 1). This information is helpful in determining the location and movement of this important feature.

Figure 1 illustrates the echo pattern associated with a strong shear area and vortex aloft near 1700Z on August 7, 1972. Earlier, severe weather had occurred in advance of this system. The severe weather will be described later in cases 4 and 5. The pattern shown in Figure 1 held together for several hours as it moved east northeastward at 18 knots. The center of the vortex, as determined from the WBRR picture, is located at 1643Z, near the north shore of Lake Erie, north of Cleveland (CLE). The 5,000 foot wind chart (Figure 2) indicates that at 1200Z a closed circulation was present in the central Great Lakes area. The surface map for 1200Z, illustrated in Figure 3, indicates a Low north of Cleveland. It is important to recognize that the level of the feature displayed on the radar readout depends on the distance detected from the radar location. The radar beam is normally tilted at one-half degree elevation. With this tilt the center of the beam at 65NM would be between 5,000 feet and 6,000 feet. At 100NM the center of the beam is about 11,000 feet. - 4 -

CLE

Figure 1. Comma-shaped radar echo pattern associated with an upper vortex, August 7, 1972. The center of a vortex is usually located near the eye of the comma. 5

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Figure 3. Surface map, 1200Z August 7, 197 2. 6 -

CASE 2

ECHO FORMATION AND MOVEMENT ASSOCIATED WITH A BUBBLE-HIGH

A convex shape to a pattern of strong echoes moving ahead of a bubble- High is a common configuration for this type of small-scale pressure system when it produces severe weather. Radar echoes associated with a bubble-High on August 10, 1972 are illustrated in Figures 4 and 5. A schematic of the echo pattern displayed at 1600Z on a WSR—3 local use radar located at Cleveland and the surface pressure pattern are shown in Figure 4. Figure 5 shows WBRR pictures with the echo pattern of Figure 4 superimposed on the picture for 1552Z, The echoes received by the Cleveland WSR—3 should relate to the stronger echo intensity levels simultaneously received by the Detroit WSR-57. For some unknown reason, the strongest intensity level shown on the WBRR (Figure 5) is moderate, although strong intensities (TRW +) with tops to 52,000 feet were reported as observed on the Detroit WSR-57.

Figure 4. Schematic of the echo ECHO pattern displayed at 1600Z on a WSR-3 local use radar located at Cleveland and the surface pressure pattern.

The leading edge of the echo line was seen on radar to be moving at about 55 knots. This indicates a very strong pressure gradient although this was not evident in the macro pressure pattern. The strongest echoes were in the southern most portion of the line with tops to 52,000 feet. When the line passed through Findlay, Ohio, (FDY) (Figure 5, 1626Z), observers there reported wind gusts to 52 knots with zero ceiling and zero visibility in very heavy rain. Bubble-Highs of this type usually last 1 to 2 hours and then lose their intensity. When the system passed through Columbus, Ohio, (about 75 miles south southeast of Findlay) winds of only 30 knots were recorded.

The type of echo pattern described here is usually related to severe thunderstorms and strong gusty winds. Gusts can be expected to reach speeds as high, and usually higher, than the line movement. Tornadoes are not common with this type of system unless a LEWP forms. 7

Figure 5. WBRR presentation of echo formation and movement associated with a bubble high on August 18, 1972. Echo pattern displayed at 1600Z on a WSR-3 located at Cleveland is drawn on the 1552Z WBRR picture.

1757Z - 8 -

CASE 3

TORNADOES ASSOCIATED WITH A HOOK ECHO AND MESO-LEWP

A series of radar echo patterns that occurred on August 17, 1972 provides us with an example of a hook echo that was discernible in the higher intensity return within a larger echo pattern (Figure 6). A meso-LEWP formation with a strong meso-scale bubble-High is also illustrated,, When echoes are strong and tops near or exceeding the tropopause, these patterns are usually accompanied by severe thunder­ storms and sometimes tornadoes. The series of pictures shown here begin at 1559Z. At this time, and shortly before, funnel clouds were reported in association with the echoes to be described. Examining the WBRR picture for 1559Z, and concentrating on the higher level echo intensity, shown by the white area within a black area, note the hook-shaped echo pattern on the 50-mile range marker. This area is about 25 miles southeast of Toledo (TOL), Tornadoes occurred within the hook pattern. The maximum top reported was 51,000 feet.

By 1607Z the white hook pattern closed, with a black hole appearing in the center. Judgement and/or coordination with the radar operator is sometimes necessary in determining whether an intensity level depicted on a WBRR picture is weaker or stronger than the surrounding area. In this case, the black hole depicted a weaker intensity level than the surrounding white, A tornado occurred at Freemont, Ohio, associated with the hook echo.

By 1614Z the black hole in the center of the echo pattern changed to white (increased in intensity level). In the WBRR pictures for 1614Z, as well as 1607Z, a LEWP is evident in the higher intensity echoes (white) extending southeastward from what was the hook formation. Annotation is used to highlight the LEWP, Tornadoes occurred near the crest of this LEWP, where tops extended to 56,000 feet. The shape of the higher intensity echoes indicates that this is a meso- LEWP with bubble-high characteristics (see Figures 4 and 5). The bowed section of the line extending southwest from the crest of the LEWP moved southeastward at 45 to 50 knots. After 1700Z (not illustrated) the LEWP lost its identity or at least appeared to. The storm was then 125 miles from the Detroit radar^ and care must be taken in evaluating the echo patterns at distances that far from the radar site.

Good examples of a hook echo, as seen on a WSR-57 PPI scope, are pre­ sented on pages 29-31, Hamilton 1969, F CASE 4

TORNADO AT VERMILION, OHIO, ASSOCIATED WITH A LEWP

The radar activity during the early morning hours of August 7, 1972, was very complex. There were heavy thunderstorms, with tops above the tropopause, but no reports of severe weather. A band of thunderstorms had moved through both Detroit and Toledo with heavy thunderstorms reported. By 0753Zja possible LEWP appeared with a crest just northwest of Sandusky (SKY) as can be seen in Figure 7, The LEWP became well defined by 0809Z moving east northeastward. A tornado touched down at Vermilion at 0820Z. No other reports of severe weather were received until a second LEWP formed east of Cleveland, and a second tornado touched down at Footsville around 1000Z. This second LEWP will be discussed later as Case 5. The 1200Z surface map for August 7 is presented in Figure 3 and the 5000 foot winds are shown in Figure 2.

The LEWP was well defined at 0809Z but the crest passed 20 miles to the north of where the tornado occurred at Vermilion. The tops exceeded the tropopause but this had been the case for several hours without any severe weather being reported. When a LEWP occurs, combined with heavy thunderstorms and tops above the tropopause, the forecaster should not limit warnings to the immediate area of the wave crest. Warnings should be considered for areas up to 60NM from the expected path of the crest. The most severe weather is frequently associated with the strongest cells in the LEWP. II

c -«>

0809Z

Figure 7. WBRR presentation of a LEWP. The crest of the LEWP moved east north­ eastward, passing just north of Sandusky (SKY). A tornado touched down at Vermilion / s (VER) at 0820Z.

0823Z 12

CASE 5

TORNADOES NEAR CLEVELAND, OHIO^ ASSOCIATED WITH A MESO-LEWP

The echo pattern that spawned a tornado at Vermilion on August 7, 1972 (Case 4) moved through the Cleveland, Ohiojarea drenching Bay Village, just west of Cleveland, with two and one half inches of rain. Intense lightning occurred as the storm moved through Cleveland, A LEWP began to form near Cleveland around 0926Z (Figure 8). A severe thunderstorm warning was issued for this storm shortly after 1000Z. Tops were around 40,000 feet and echo intensity was classed as moderate. The warning was issued since a LEWP formation is frequently associated with some type of severe weather, and it was recognized that the radar under­ estimates the true intensity of an echo at a range of 100NM, A confirmed tornado occurred around 1010Z near Geneva, Ohio^which is located about 35 miles east northeast of Cleveland. This tornado wasn't reported until about 1400Z, when a radio station called in. The storm moved from the south southwest to the east northeast although the LEWP was moving from the west.

It is interesting to note in this case, as with the previous case, that the echoes were very strong with tops above the tropopause; however, the only time severe weather occurred was when the LEWP developed. The LEWP in this case can be classed as a meso-LEWP, Figure 8. WBRR presentation of a LEWP, August 7, 1972. The LEWP formed near Cleveland (CLE) and moved eastward. A tornado occurred around 1010Z near Geneva, Ohio, which is located about 35 miles east northeast of Cleveland.

1024Z - 14 -

CASE 6

RADAR ECHO PATTERN INDICATIVE OF FLASH FLOODING

Some of the echo patterns which can produce flash flooding are: (1) slow moving or stationary echoes of heavy intensity; (2) a series of heavy echoes each of which moves over the same area; (3) continued echo development in the same area. Even echoes of moderate intensity which remain in the same area for several hours may produce flash flooding depending on topography and the hydrological conditions in the area. Moderate echoes should be carefully evaluated at ranges beyond about 70NM because at these ranges the rainfall rate determined by radar may be underestimated. The key is to watch for areas with nearly continuous echo coverage, evaluate the theoretical radar-determined rainfall in that area, and check with rainfall observers in suspect areas.

During the afternoon of September 17, 1972, heavy thunderstorms developed in an east-west line across northern Ohio. By 2112Z, tops reached 48,000 feet with several cells of strong intensity indicating heavy rain (Figure 9). In the following hour the line moved only about 10 miles to the north, and tops increased to 55,000 feet. The radar operator at Detroit was now indicating that the line was stationary with individual cells moving northeastward at 12 knots along the line. New thunderstorms continued to form to the southwest of Cleveland and move northeastward. From 2112Z to OOOOZj the heaviest thunderstorms were occuring to the west southwest of Cleveland with moderate to heavy thunderstorms continuing over much of north central Ohio. From 0000Z until 0200Z, there was a break in activity in north central Ohio as new activity developed further west. During the remainder of the night an area known as Columbia Station, located approximately 12 miles west southwest of the Cleveland Airport, received additional rain of moderate intensity while only light rain occurred at the Cleveland Airport.

In this case, the heaviest rain was measured at Columbia Station. Nine to ten inches fell there between 2100Z and 0200Z. Before the rain ended on the following morning, one observer in Columbia Station reported 12 inches and several other persons reported 10- inch buckets overflowing. To illustrate how localized this heaviest rain was, observers 2 miles away reported 4 to 5 inches and only .81 inches occurred 12 miles away at the Cleveland Airport. 15

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(Figure 9 continued on next page.) 16

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REFERENCES

Hamilton, Robert E., "A Review of Use of Radar in Detection of Tornadoes and Hail," ESSA Technical Memorandum WBTM-ER-34, U. S. Department of Commerce, Weather Bureau Eastern Region, Garden City, NY, December 1969, pp. 29-31.

Nolen, R. H., "A Radar Pattern Associated with Tornadoes," Bulletin of the American Meteorological Society, Vol. 40, 1959, pp. 277-279.

Pautz, M., and Doloresco, "On the Relation between Radar Echo Tops, the Tropopause, and Severe Weather Occurrences," Proceedings of the Tenth Weather Radar Conference, American Meteorological Society, Boston, MA, pp. 51-56. LIST OF EASTERN REGION TECHNICAL MEMORANDA l Continued lru,idn ^Kont coveA]

NWS ER 40 Use of Detailed Radar Intensity Data in Mesoscale Surface Analysis, Robert E. Hamilton. March 1971 (COM-71-00573)

NWS ER 41 A Relationship Between Snow Accumulation and Snow Intensity as Determined from Visibility. Stanley E. Wasserman and Daniel J. Monte. May 1971 (COM-71-00763)

NWS ER 42 A Case Study of Radar Determined Rainfall as Compared to Rain Gage Measurements. Martin Ross. July 1971 (COM-71-00897)

NWS ER 43 Snow Squalls in the Lee of Lake Erie and Lake Ontario. Jerry D. Hill. August 1971 (COM-71-00959)

NWS ER 44 Forecasting Precipitation Type at Greer, South Carolina. John C. Purvis. December 1971 (COM-72-10332)

NWS ER 45 Forecasting Type of Precipitation. Stanley E. Wasserman. January 1972 (COM-72-10316)

NWS ER 46 An Objective Method of Forecasting Summertime Thunderstorms. John F. Townsend and Russell J. Younkin. May 1972 (COM-72-10765)

NWS ER 47 Forecast Cloud Cover Study. James R. Sims. August 1972 (COM-72-11382)

NWS ER 48 Accuracy of Automated Temperature Forecasts for Philadelphia as Related to Sky Condition and Wind Direction. Robert B. Wassail. September 1972 (COM-72-11473)

NWS ER 49 A Procedure for Improving National Meteorological Center Objective Precipitation Forecasts. Joseph A. Ronco, Jr. November 1972 (COM-73-10132)

NWS ER 50 PEATMOS Probability of Precipitation Forecasts as an Aid in Predicting Precipitation Amounts. Stanley E, Wasserman. December 1972 (COM-73-10243)

NWS ER 51 Frequency and Intensity of Freezing Rain/Drizzle in Ohio. Marvin E. Miller. February 1973 (COM-73-10570)