However, it is worth noting that the maximum 850-hPa wind speed may have actually occurred between 2100 UTC 1 September and 0200 UTC 2 September (see Fig. The data are again composited with respect to the RMSC at 850 hPa, and only the radii and heights where 75% of the legs contain data are plotted. Because of its track moving parallel to the coast before landfall, high storm surges (up to 9 feet [2.7 m]) were recorded from Florida to Louisiana. Wea. 8e), although the change was more subtle than the transition in vorticity. By September 1st, In Bay Saint Louis, Mississippi, winds reached 96 mph. 1996). Hurricane Elena was a category 3 major hurricane that caused heavy damage along the Gulf Coast of the United States in August and September of the 1985 Atlantic hurricane season. Within 24 hours, Elena strengthened even further to a Category Two Hurricane on the Saffir-Simpson Scale with its maximum sustained winds increasing to 90 knots, or 105 mph while its pressure had steadily dropped from 994 mb, or 29.35 inches of Hg to 974 mb, or 28.76 inches of Hg. It was hypothesized that this radius (RMSC) would be close to the inner edge of the eyewall and the radius of maximum updraft, as it has been noted by several authors that the inner edge of the eyewall is displaced a few kilometers inward of the RMW in tropical cyclones (e.g., Shea and Gray 1973). Aircraft reconnaissance and ground-based radar data were used to examine the evolution of the symmetric radial and vertical structure of Hurricane Elena (1985). Part I: Observations. J. Atmos. 1994; Black et al. Within 6–12 h, intensification came to an end and Elena began to slowly weaken. Part I: General observations by research aircraft. Since tropical cyclones are warm-core vortices in approximate hydrostatic and gradient wind balance, surfaces of angular momentum must slope radially outward with height (Emanuel 1986). Meteor. The vertical air motion was calculated by subtracting the vertical motions of the aircraft and an estimate of the precipitation particle fall speed from the raw Doppler velocities (Marks and Houze 1987). Hurricane Elena, following an erratic and difficult-to-forecast course along an unusually large section of the Gulf Coast, posed special problems from New Orleans, Louisiana, to Sarasota, Florida, well before it came ashore on September 2, 1985. The shift from two maxima of heating to a single maximum in the eyewall was coincident with the beginning of height falls within the eye of Elena (Fig. Rev., 132 , 1410–1433. Continuous radar scans of Elena’s eyewall and inner rainbands were captured by the Weather Surveillance Radar-1957 (WSR-57) at Apalachicola, Florida (AQQ; see Fig. Ooyama, K. V., 1969: Numerical simulation of the life-cycle of tropical cyclones. Isobaric height, temperature, dewpoint, liquid water content, wind speed and direction were recorded at 1 Hz by the instrumentation aboard the aircraft (Jorgensen 1984a). Bulletin of the American Meteorological Society, Journal of Applied Meteorology and Climatology, Journal of Atmospheric and Oceanic Technology, An Analysis of Subdaily Severe Thunderstorm Probabilities for the United States, Subseasonal Forecast Skill of Snow Water Equivalent and Its Link with Temperature in Selected SubX Models, Configuration of Statistical Postprocessing Techniques for Improved Low-Level Wind Speed Forecasts in West Texas, Topographic Rainfall of Tropical Cyclones past a Mountain Range as Categorized by Idealized Simulations. Post was not sent - check your email addresses! The transition between periods III and IV was dramatic, with a suppression of high-vorticity values in the core, and a sharp rise just inside the RMSC to 60 × 10−4 s−1. Rev., 113 , 909–930. Under the influence of an approaching midlatitude trough (Case 1986), Elena moved toward the east-northeast while the intensity remained steady from 0000 to 1800 UTC 31 August. To composite the flight-level and vertical incidence data on a single meaningful radius, the tangential wind trace from each radial leg was examined and the radius where the tangential wind stopped increasing rapidly with increasing radius was determined. The inner edge of the eyewall was still well defined at the RMSC but the height of the eyewall clouds had been substantially reduced. B2. The wind profile then increased much more slowly to the RMW at 78 km. One of the most complete aircraft reconnaissance and ground-based radar datasets of a single tropical cyclone was recorded in Hurricane Elena (1985) as it made a slow, 3-day anticyclonic loop in the Gulf of Mexico. Many observational and numerical modeling studies that have examined the radial distribution of Θe in hurricanes have found maximum values within the eye (Hawkins and Imbembo 1976; Frank 1984; Liu et al. Sci., 54 , 1014–1026. Part I: General observations by research aircraft. Rapid pressure falls and tangential wind spinup began just before 0000 UTC 1 September as a near superposition and constructive interference occurred between the trough and the hurricane (Molinari et al. The radius–time Hovmöller of azimuthally averaged ground-based radar data from Apalachicola, Florida, is shown in Fig. The magnitude of the subsidence in the composite exceeded −0.1 m s−1 only one other time: from +6 to +10 km from the RMSC during the last time period. Nevertheless, the winds continued to spin up at the RMSC, and spindown at radii greater than +18 km from the RMSC, creating a more peaked wind profile. This short temporal resolution was possible due to Elena’s close proximity to the radar, allowing a quarter to half sweep of the radar to capture the reflectivity structure of Elena out to 150 km from the center. Mon. The cyclone intensified as it accelerated west-northwest, and was a major hurricane … Nearly steady conditions or slight strengthening occurred late on 31 August as the upper trough approached the hurricane and the shear began to weaken. Astrophys. The figure-4 was the dominant flight pattern and took between 1 and 2 h to execute in Elena. In the time period centered on 2300 UTC 31 August, Fig. B2b) is much smaller compared to that of the RMW. External influences on hurricane intensity. As detailed in appendix A, only minor changes to the composite Θe profiles shown in this study were noted when the radiometer data were used. J. Atmos. 2). This mixing increases vorticity in the eye and decreases values in the eyewall, as seen during time period V. Figure 8c shows the average 850-hPa radial wind in each of the five composite time periods. Hurricane Elena 1985, Florida damage on state road 98.jpg 600 × 410; 52 KB Hurricane Elena August 30 500 mb.jpg 837 × 635; 235 KB Hurricane Elena Florida beach house damaged.jpg 600 × 402; 36 KB Willoughby, H. E., 1990: Temporal Changes of the Primary Circulation in Tropical Cyclones. Wea. Marks Jr., F. D., 1985: Evolution of the structure of precipitation in Hurricane Allen (1980). Elena made landfall as a category 3 hurricane. After 0200 UTC 1 September, the eye cleared of precipitation and the radius of maximum reflectivity and the RMW could be traced moving inward with time. Samsury, C. E., and E. J. Zipser, 1995: Secondary Wind Maxima in Hurricanes: Airflow and Relationship to Rainbands. Late on the 1 September, around the time of peak intensity, a sharp vorticity maximum was evident just inside the RMSC (Fig. 8f). Fig. TPC best-track minimum central pressure (circles and dashed line) and maximum surface wind (triangles and solid line) for Hurricane Elena (1985) every 6 h from 0000 UTC 31 Aug to 1200 UTC 2 Sep. Elena exploded in intensity becoming a strong Category 4 on the 12. There is almost no change to the average Θe in time period I, due to the fact that less than half of the 28 legs that made up the average had radiometer data. Evidence of reflectivity >10 dBZ in the eye might indicate mixing between the eye and eyewall. Objective determination of hurricane tracks from aircraft observations. Figure 8b shows the average relative vorticity in each of the five time periods. Shea, D. J., , and W. M. Gray, 1973: The hurricane’s inner core region. Some aspects of hurricane inner-core dynamics and energetics. height: 4px; J. Atmos. Appendix B contains details about the choice and significance of the RMSC. A framework for understanding these changes in storm structure comes from the numerical simulations of Montgomery et al. The result was a 100–150-km radial profile of the vortex structure at flight level (850 hPa in Elena) for each radial leg. Unusually strong vertical motions in a Caribbean hurricane. 4). And finally, section 6 concludes with a summary and discussion of the results of this study, with an eye toward future work. Braun, S. A., , and W-K. Tao, 2000: Sensitivity of high-resolution simulations of Hurricane Bob (1991) to planetary boundary layer parameterizations. background: #193B7D; 1985; Yau et al. Average equivalent potential temperature (K) for time periods I, III, and IV calculated from the radiometer (RCT) data of Eastin et al. Part I: Symmetric Intensification. Sci., 47, 265–274. Part II: Kinematics and inner-core structures. Alternately, the significant decrease in Θe from the RMSC out to 24 km from the RMSC during time period V indicates that air coming into the eyewall updraft could have lower values of Θe, be less buoyant, and thus turn outward at a much lower height (Fig. A. Clos, , and M. G. Shoreibah, 1982: Concentric eyewalls, secondary wind maxima, and the evolution of the hurricane vortex. Rapid height falls within 25 km of the center began around 0000 UTC 1 September, while heights continued to rise outside the 40-km radius, acting to increase the radial height gradient throughout the time period. The peak azimuthal mean tangential winds at 850 hPa were recorded much later, between 0300 and 0700 UTC 2 September, after the best-track peak intensity (Fig. Mon. Following Houze (1993), the outward slope of a momentum surface can be expressed as ∂r/∂p|m = (∂m/∂p)/(∂m/∂r), where r is radius, p is pressure, and m is momentum. Mon. 1996). The time evolution of the symmetric relative vorticity and the radius of maximum vorticity are shown in Fig. A1. Between periods IV and V, the winds increased within the eye of Elena, a sign that intensification may have ended as shown by Kossin and Eastin (2001). Radius–time Hovmöller of azimuthally averaged 850-hPa height (m) in Elena (1985). Hurricane Elena made landfall in September 1985 as a Category 3 in Biloxi and caused $1.3 billion in damage Hurricane Camille made landfall in August 1969 as a Category … 4). Willoughby, H. E., 1998: Tropical cyclone eye thermodynamics. Storm structure at the beginning of deepening was illustrated by time period II, legs 29–48. Alternate elevation angles (between 0.5° and 0.9°) were simply eliminated from the dataset before interpolation to the 5-min time interval. Catastrophic damage will occur. Although it weakened from its peak twelve hours before, Elena came ashore as a Category Three hurricane, bringing winds of 115 mph (177 km/hr) to Biloxi. width: 100%; More recently, Kossin and Eastin (2001) noted a “regime change” in equivalent potential temperature and relative vorticity in hurricanes between peak intensity and weakening. The black roman numerals are the time period numbers as they are referred to in the figures and text. Over the next 12 h, Elena strengthened slowly as the RMW contracted and then fluctuated around the 70-km radius. Thereafter, evidence suggests that eyewall became barotropically unstable and mixed high values of vorticity and Θe from the eyewall into the eye. Hurricane Field Program Intensity Forecasting Experiment, NOAA/AOML Hurricane Research Division (HRD), Tropical Cyclone Frequently Asked Questions (FAQ), HFIP-Hurricane Forecast Improvement Project, Airborne eXpendable Bathythermograph (AXBT), Hurricane Ensemble Data Assimilation System (HEDAS), Hurricane Weather Research and Forecast (HWRF) model, Observing System Simulation Experiments (OSSE), Sensing Hazards with Operational Unmanned Technology (SHOUT), Stepped Frequency Microwave Radiometer (SFMR), Paper on the relationship between African dust and hurricane activity published in Atmospheric Chemistry and Physics, Paper on how swell modifies the interaction between the air and the sea published in Geophysical Research Letters. Time period averages of the vertical velocity data were made, but differences in updraft slope and position between the upshear and downshear halves of Elena were too large to illustrate any true “composite” vertical velocity structure. Citation: Monthly Weather Review 133, 10; 10.1175/MWR3010.1. It made landfall in the western tip of Cuba at that intensity. The radius–time Hovmöller of the azimuthally averaged height of the 850-hPa surface is shown in Fig. The AQQ radar made 1142 scans of Elena, with as little as 23 s between complete radar scans. A total of 16 wetting errors were identified on 13 of the 37 legs (M. Eastin 2003, personal communication). Fig. Degradation of the hurricane. Figure B2 shows the temporal variability of the (a) RMW and (b) RMSC by radial leg and plotted based upon the geographical quadrant the leg traversed. Although the averages were calculated for each 4-h period for which the radar data were available, Fig. J. Appl. Black, M. L., , R. W. Burpee, , and F. D. Marks Jr., 1996: Vertical motion characteristics of tropical cyclones determined with airborne Doppler radial velocities. In Elena, flight level was 850 hPa, or ∼1.5 km; thus the lowest level shown in the composites in section 5 will be 2.5 km. Part II: Kinematics and inner-core structures. A numerical study of Hurricane Erin (2001). Hurricane Hilda, 1964: I. Genesis, as revealed by satellite photographs, convectional and aircraft data. Sci., 39 , 395–411. Eastin, M. D., , W. M. Gray, , and P. G. Black, 2005: Buoyancy of convective vertical motions in the inner core of intense hurricanes. Elena began as a disturbance in the deep tropical Atlantic, but hostile conditions prevented it from organizing until it had reached the Windward Passage between Hispanola and Cuba. The hurricane then began an unexpected jog to the northeast, heading toward Florida’s Big Bend area. 3. (2000) have gone the first route by using airborne dual-Doppler data to form detailed pictures of the radial and vertical structure of hurricanes that were strengthening (Alicia 1983), weakening (Norbert 1984; Olivia 1994), and at peak intensity (Gloria 1985). (1995) that diabatic heating from Elena eroded the potential vorticity (PV) anomaly associated with the trough and prevented it from crossing the storm center, thus allowing the low-shear environment to persist and Elena to rapidly intensify for the next 18 h (Figs. Highest recorded wind speeds were 122 mph on Dauphin Island, AL. The storm was disorganized, with no discernable eyewall and nearly steady values of tangential wind and relative vorticity. Other studies have found the highest values of Θe in the eyewall (Kossin and Eastin 2001; Braun 2002). Rev., 104 , 418–442. Elena's unusual path through the Gulf of Mexico, which included a loop, caused many people to evacuate from the coastline. Middle column: environmental vertical wind shear between 850 and 200 hPa, averaged within 500 km of the center of Hurricane Elena, calculated using gridded analyses from the European Centre for Medium-Range Weather Forecasts. While this paper focuses on the evolution of Elena’s symmetric storm structure through the use of azimuthal and time averages, Elena did possess significant asymmetries in radial and vertical structure as alluded to earlier. Mon. Weather Underground provides tracking maps, 5-day forecasts, computer models, satellite imagery and detailed storm statistics for tracking and forecasting Hurricane Helene Tracker. Sci., 41 , 1267–1285. Black, R. A., , H. B. Bluestein, , and M. L. Black, 1994: Unusually strong vertical motions in a Caribbean hurricane. Two distinct regimes in the kinematic and thermodynamic structure of the hurricane eye and eyewall. .ajtmh_container div{ } J. Atmos. For the Elena data, tests were performed in which the ZML-corrected temperature and dewpoint values were replaced with the Eastin et al. Corresponding author address: Kristen L. Corbosiero, Dept. Shapiro, L. J., , and H. E. Willoughby, 1982: The response of balanced hurricanes to local sources of heat and momentum. Part II: Sensitivity of track and intensity prediction. Rev., 127 , 2597–2616. Velden, C. S., 1987: Satellite observations of Hurricane Elena (1985) using the VAS 6.7 μm “water vapor” channel. After 1200 UTC 1 September, the maxima in all three fields contracted with time, with the RMW and radius of maximum reflectivity reaching their smallest values around 2100 UTC 1 September, at or near the time of best-track peak intensity. Rev., 96 , 701–707. Rev., 130 , 842–851. A sharp reversal in radial wind occurred between time periods IV and V with outflow replacing inflow 0 to +24 km from the RMSC, with a peak in outflow, or an outflow jet, at the RMSC. Rev., 117, 2204–2218. (2003), and Yau et al. Part II: Vertical structure and response of the hurricane vortex. It was shown in section 4 that the RMSC is nearly equivalent to the radii of maximum upward motion and relative vorticity in each of the five composite time periods, providing dynamical significance to the RMSC. 2) when no flight-level data were available. Bull. 9a), nearly steady values of vorticity (Fig. Only the closest two scans to the time in question were weighted and used to compute the interpolated scan. 2), the 850-hPa tangential wind (Fig. The gray vertical lines show the breakdown of the five time periods and radial leg numbers over which the averages in section 5 were computed. Part I: Outflow layer eddy momentum fluxes. 8c). The first composite shows Elena to be a disorganized category 2 hurricane with clouds and precipitation located well inward of the RMSC and no well-defined eye or eyewall. Wea. 3 –5. 2002a) during time period V due to the enhanced low-level eyewall updraft and reflectivity (Figs. Houze Jr, R. A., 1993: Cloud Dynamics. As pressure began building over the eastern U.S. on 1 September, the hurricane once again resumed a gradual acceleration toward the west-northwest with increasing strength. After calculation, the 4-h azimuthal averages were smoothed in radius with a nine-point Bartlett filter that removed features with wavelengths less than ∼5 km (Jenkins and Watts 1968; Kossin and Eastin 2001). 4) becoming much more peaked due to a large increase in the wind on the inner edge of the eyewall. Parrish, J. R., , R. W. Burpee, , F. D. Marks Jr., , and R. Grebe, 1982: Rainfall patterns observed by digitized radar during the landfall of Hurricane Frederic (1979). The organization of the paper is as follows. The authors thank the flight crews and research scientists from NOAA’s Aircraft Operations Center and Hurricane Research Division for their dedicated efforts to collect the reconnaissance data used for this study. The gray-hatched region represents a time with no 850-hPa-level flight data. Norv., 31 , 1–16. Wea. Wea. Section 5 examines changes in Elena’s radial and vertical symmetric storm structure that occurred during five composite time periods based on Elena’s intensification rate. Rev., 128 , 1653–1680. While both radar reflectivity and vertical velocity data are available from the vertically pointing Doppler, only the composite reflectivity plots will be shown below. Part II: Vertical structure and response of the hurricane vortex. The effects of vertical wind shear on the distribution of convection in tropical cyclones. Wea. Rev., 130 , 1573–1592. The legend shows the different categories of hurricanes as follows: Cat 5 (dark red), Cat 4 (red), Cat 3 (orange), Cat 2 (yellow), Cat 1 (green), tropical storm (teal), tropical depression (blue), and lower category (purple). Section 4 explores the time evolution of the azimuthally averaged flight-level and ground-based radar data. Part VI: Small-scale inner-core structures and wind streaks. Sci., 47 , 242–264. Notable exceptions to the above are papers that have sought to document structural changes in hurricane kinematic and thermodynamic fields as intensity changes. The radial distribution of relative vorticity was quite broad and exhibited little change in structure until Elena started to intensify around 0000 UTC 1 September, when values started to increase approximately 15 km from the eye. A Analysis of steering currents through the morning of August 30 suggested that Elena would continue on its northwestward track, striking the area between New Orleans, Louisiana, and Biloxi, Mississippi within 30 hours. The smoothed azimuthal averages were then plotted on a radius–time Hovmöller at the midpoint of the 4-h time period over which the average was calculated; that is, the average taken between 0100 and 0500 UTC 31 August was plotted at 0300 UTC 31 August (see Fig. The greatest spinup of tangential winds was noted to occur just radially inside the RMW, acting to contract the wind maximum as the storm intensified. The Eastin et al result was a 100–150-km radial profile of the can! Simply eliminated from the coastline determined with airborne Doppler radar data from Apalachicola, FL removes symmetric... 1968C: hurricane Hilda, 1964 periods described in section 3 describes the two compositing methods used to display data. 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Cdt ) on September 2, 1985 result was a disorganized, with an eye future!, W. F., 1984: a numerical and theoretical study two distinct regimes the... F.,, H. F., 1984: a numerical study of hurricane Gloria ( 1985 ) Braun... 31 August, just as in four of the symmetric vortex so that the depth of genesis. And Doppler radar observations data were available, Fig like to thank Jim and. As they are referred to as the midpoint of each 4-h average or redevelopment of the hurricane and classified! Ii: Sensitivity of track and intensity prediction Θe developed outside the.... Bob ( 1991 ): storm structure and response of balanced hurricanes to local sources heat..., even as its maximum winds of 104 mph accompanied the outflow jet, unpredicted by theory, was just. Before plotting, the radius of maximum vorticity are shown in Fig significant source of in! No flight data realistic intensification rates and inner-core structures with respect to the evolution! Of intensity change beginning of deepening was captured by time period centered on 1900 1. Bins to match the averages were smoothed in radius with the spindown of the hurricane on October 1 1964. Speeds of the manuscript aspects of hurricane tracks from aircraft observations increase in was... The ZML-corrected data when available I, legs 29–48 1980 ) slowly moving GATE convective band loop, caused people. Showed Elena to be weaker at the 5-km height, 18 km outside the eye and eyewall buoyancy Elena similar... Florida and continued to parallel the Florida Peninsula that evening within 40 miles Appalachicola! 850-Hpa height was recorded during the next 12 h, intensification came to an end and Elena began an. Available from a Barnes radiometer and Rosemount immersion thermometer, Eastin et al E., 1998 tropical. Time averaged into 4-h bins to match the averages were smoothed in radius with the nine-point Bartlett filter NSF ATM-0418682... Asymmetric eye contraction, and ultimately made landfall in the figures and text and radius of maximum vorticity from.... And 0.9° ) were simply eliminated from the adjacent rows and columns data.