A Handbook for Visual Identification


Fernando Caracena, NOAA/Forecast Systems Lab*

Ronald L. Holle, NOAA/National Severe Storms Lab*

Charles A. Doswell III, NOAA/National Severe Storms Lab*


* Affiliations at the time of publication - All now retired from NOAA

Figure Captions

Most recent update: 9 February 2011: Moved to my home website and updated


NOTE #1: If there is no image shown for a caption, that image is unavailable for inclusion here.

NOTE #2: We gratefully acknowledge the permission granted by the copyright holders for the use of these images in this Web version of the Microburst Handbook. Any image not specifically noted as copyrighted is in the public domain, and can be used freely. Copyrighted images are indicated as such; please contact the image authors for information about any use of these images.

Figure 1. Locations and times of well-known aircraft accidents associated with microbursts, 1975-1985.

Figure 2. A gust front photographed in South Florida during the Florida Area Cumulus Experiment. The front, made visible by dust, is moving to the right, where lifting is producing cumulus clouds (upper right). The characteristic profile produced by the sinking of rain-cooled air extends farther forward near the ground but is retarded at the surface by friction. Gust fronts are much more widespread than microbursts, often extending over tens of kilometers. (NOAA Photograph, taken by Irv Watson)

Figure 3a. A typical patch of microburst wind damage, produced by the Independence Day storm that moved across northern Wisconsin in 1977 (Fujita 1978). (Photograph ©1978, T.T. Fujita)

Figure 3b. Typical appearance of a microburst on Doppler radar as observed during the Joint Airport Weather Studies project. (Photograph courtesy of John McCarthy, ©1982 National Center for Atmospheric Research/National Science Foundation)

Figure 4. Cross section of a conceptual vortex ring model of a microburst (Caracena 1982; 1987). The shaded portion is the friction boundary layer that contains vorticity opposite to that of the descending ring.

Figure 5. Numerical simulation of a wet microburst by Droegemeier, showing part of the distribution of rainwater mixing ratio shaded in increments of 0.007 g per kg (maximum simulated value was 0.119 g per kg) and streamlines depicting the circulation.

Figure 6. A microburst-bearing rainstorm that moved over the northern portion of Stapleton International Airport (Denver, Colorado) on 7 August 1977; the picture was taken minutes after a plane crash. The crashed aircraft and dust mixed with smoke are visible to the left of the rain shaft (left center). The upward curl of the microburst is visible on the right of the rain shaft and has ascended several kilometers toward the base of the cumulonimbus. Dust clouds widen the base of the rain shaft, indicating that the rain shaft is the source of outwardly driving surface winds. Note that dust and smoke are visible blowing toward the left, opposite to the motion of the upward curl on the right.

Figure 7. A vertical cross section through the microburst involved in the 2 August 1985 airplane crash at Dallas-Fort Worth International Airport, constructed from the digital flight recorder data and based on the conceptual model (Fig. 4). Potential temperature (kelvins) is contoured and color coded. Dark blue represents the coldest temperatures; red represents the warmest. Wind data are represented by vector (scale at upper left) along the flight track. General vortex circulation is indicated by the streamlines. Fujita (1986) produced a similar analysis. (From Caracena et al. 1986)

Figure 8. Conceptual models of environmental opposite extremes associated with microbursts. (Left) The dry extreme is characteristic of semi-arid regions of the West, where rain showers virtually evaporate before reaching the surface, but nevertheless produce destructive winds. (Right) The wet extreme is characterized by a dry source layer that ejects pockets of dry air into underlying rain-filled and saturated air, producing the evaporation that can result in a microburst. Note that the two panels are not to scale regarding cloud tops, which extend no higher than 7 km (23,000 ft) AGL in dry microburst storms and as high as 15 km (49,000 ft) AGL in wet microburst storms.

Figure 9a. A composite of five afternoon (0000 UTC) soundings by Brown et al. (1982) for convective events that produced damaging surface winds associated with high-based cumulonimbi in the Front Range area of Colorado. The temperature is represented by the curve on the right, and the dew point temperature by the curve on the left. The sounding is also typical of the type of environment found, during JAWS, to be associated with large numbers of microbursts (Caracena and Flueck 1988). The sounding shows the characteristic deep, dry mixed layer with dry adiabatic lapse rate, of ~9.8oC km-1 (~5.4oF per 1000 ft) topped by a moist, cloud-bearing layer (low dew point depression).

Figure 9b. A dry microburst sounding, as in Fig. 9a, but taken in the morning (1200 UTC) of 31 May 1984, showing the kind of shallow inversion near the surface that usually disappears later in the day to produce a sounding like Fig. 9a, thereby implying a high potential for dry microbursts later in the day. This sounding was taken about 7 hours before a microburst-related near-accident at Stapleton International Airport.

Figure 10. A typical wet microburst sounding taken at 1500 UTC, 1 July 1975, just south of Lake Okeechobee at the Field Observing Site of the Florida Area Cumulus Experiment just 3 hours before a microburst embedded in a gush of heavy rain struck the very same site. Note the elevated dry layer centered at about 400 mb that could act as a source of the potentially cool downdraft described in Fig. 7. The right-hand heavy dashed line represents a hypothetical downdraft that produces a maximum wind speed of 22 m s-1 (43 kt); the left-hand heavy dashed line represents a downdraft colder by 1oC (1.8oF) that produces a maximum wind gust of 31 m s-1 (60 kt). (From Caracena and Maier, 1987)

Figure 11. Reconstructed sounding for Dallas-Fort Worth International Airport for a time when a microburst-related accident happened. This sounding shows the characteristics of a dry microburst environment as described in Fig. 7, but with abundant precipitable water because of the lower elevation of the site. The high microburst potential is indicated here by a rather deep mixed layer about 3 km (10,000 ft), a moist cloud-bearing layer at 700 mb, and a dry layer at about 500 mb. The area shaded light gray represents positive buoyancy in the updraft. The area shaded dark gray represents negative buoyancy in the downdraft, which corresponds to an estimated maximum wind gust of 35 m s-1 (68 kt).

Figure 12. A typical high-based thunderstorm that can produce downbursts, but little or no rain at the surface. The picture was taken on 29 August 1979 at about 1750 MDT, looking east from Boulder County Airport, Colorado. (Photograph ©1980, F. Caracena)

Figure 13. A dry microburst (small ring of dust, bottom left) just beginning to form under a prominent virga shaft (top center) extending below the high base of a cumulonimbus. (Photograph ©1982, National Center for Atmospheric Research/National Science Foundation; taken by E. Szoke, 14 July 1982, during JAWS)

Figure 14. The dry microburst pictured in Fig. 13, photographed a few minutes later when the ring of dust had expanded and developed further. (Photograph ©1982, National Center for Atmospheric Research/National Science Foundation; taken by E. Szoke, 14 July 1982, during JAWS)

Figure 15. A close-up of a ring of dust associated with a dry microburst photographed 27 km (15 n mi) east of Stapleton International Airport on 14 July 1982 during JAWS. (Photograph ©1985, T. Fujita)

Figure 16. Part of dry microburst, photographed at close range from the Denver-Stapleton Control Tower, in the summer of 1984. (Photograph ©1984, National Center for Atmospheric Research/National Science Foundation; taken by W. Schreiber)

Figure 17a. A fair-weather-appearing sky in which dry microbursts later developed, near Abernathy, Texas, on 21 May 1986. The only clue to potential microburst development is the combination of a fibrous appearance of the clouds and incipient virga shafts of some of the clouds. (Photograph ©1986, C.A. Doswell III)

Figure 17b. A dry microburst rendered visible by blowing dust in the general area shown in Fig. 17a, about 20 minutes later. (Photograph ©1986, C.A. Doswell III)

Figure 18. Downbursts forming under a large thunderstorm anvil west of Hobbs, N. Mex., May 1986. The downbursts are far from the parent updraft (off-camera) that produced hail. (Photograph ©1986, C.A. Doswell III)

Figure 19. A gust front vortex of tornadic strength (gustnado) and blowing dust spawned by a high-based storm along the landing approach to Denver's Stapleton International Airport, 1984. The light from an aircraft attempting to land is visible through the gustnado. (Photograph ©1984, National Center for Atmospheric Research/National Science Foundation; taken by W. Schreiber)

Figure 20. A high-based thunderstorm near Stapleton International Airport during the CLAWS project (1984), producing heavy rain at the surface with a characteristic foot-shaped bulge between cloud base and the surface (right of center) extending outward from the center of the rainshaft. The bulge marks strong horizontal winds characteristic of a microburst that carry precipitation outward from the impact center of the downdraft. (Photograph ©1984, National Center for Atmospheric Research/National Science Foundation; taken by W. Schreiber)

Figure 21a. A wet microburst embedded in heavy rain in western Texas, 1 June 1985. Strong horizontal winds drive rain near the ground well beyond the edge of the rain shaft (on the right side of photograph). Note the plume of dust (center bottom) beginning to curl up from a plowed field. (Photograph ©1985, C.A. Doswell III)

Figure 21b. The microburst shown in Fig. 21a, a few minutes later. This view shows the rapid changes in the dust plume, including a weak vortex along the outflow boundary as a concentrated dust mass (bottom left center). (Photograph ©1985, C.A. Doswell III)

Figure 22a. A globular mass of heavy rain descending (left) near the edge of a more extended rain shaft (right). Such a mass bay be the indicator of a descending microburst. (Photograph ©1982, National Center for Atmospheric Research/National Science Foundation; taken by E. Szoke during JAWS)

Figure 22b. The globular mass shown in Fig. 22a, less than a minute later. It is reaching the surface; a clearing above it is suggestive of a strong downdraft, further indication of a possible microburst. (Photograph ©1982, National Center for Atmospheric Research/National Science Foundation; taken by E. Szoke during JAWS)

Figure 23a. A medium-based thunderstorm near Knox City, Texas, 15 May 1986, in the process of producing a wet microburst. Note the plume of dust beginning to rise from the surface, to the right of the rain shaft. (Photograph ©1986, C.A. Doswell III)

Figure 23b. The storm shown in Fig. 23a, a few tens of seconds later. The plume of blowing dust has rapidly expanded. (Photograph ©1986, C.A. Doswell III)

Figure 24. A tall maturing cumulonimbus cloud southern Oklahoma on 5 May 1976, showing evidence of strong outflow near the surface in the outward slope of the rainshaft and the faint suggestion of a precipitation curl under the lowered updraft base (bottom center), possibly indicating a microburst. (Photograph ©1976, C.A. Doswell III)

Figure 25. A wet microburst on 20 May 1974, characterized by a well-defined foot shape on the left side of the rainshaft. (Photograph ©1974, C.A. Doswell III)

Figure 26. A wet microburst near Alvord, Texas, 13 May 1986, characterized by the well-defined foot (right of center) and low-level scud clouds condensing on the leading edge of the outflow (above the "toe"). (Photograph ©1986, C.A. Doswell III)

Figure 27. A group of localized rain shafts in south-central Oklahoma, 23 May 1981. The faint upward curls near the ground (left of center) are suggestive of microbursts. (Photograph ©1981, C.A. Doswell III)

Figure 28. A "normal" midafternoon, midsummer wet microburst photographed on 1 July 1978 west of Wichita, Kansas (looking south) at intervals of a minute or less. The intervals are about the same as those in Fig. 29, and the corresponding phases of evolution of the two microbursts are displayed right after each other in the following series. (Photographs ©1978, Michael Smith, provided courtesy of Michael Smith and WeatherData, Incorporated)

Figure 28. (Continued)

Figure 28. (Continued)

Figure 28. (Continued)

Figure 28. (Continued)

Figure 28. (Continued)

Figure 29. An unusual wet microburst over the desert at night, photographed at Tucson lighted by frequent lightning. The intervals are about the same as those in Fig. 28, and the corresponding phases of evolution of the two microbursts are displayed right after each other in the following series. (Photographs ©1984, M. Maier)

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