Wind Effects on Asphalt Shingles
Timothy P. Marshall, Haag Engineering Co., Irving, TX; and R. Herzog, S. M. Morrison, and J. Green -
This paper will explore various failure modes of asphalt shingle roofs in windstorms. Roofs in three subdivisions were analyzed after Hurricane Frances struck Florida in 2004. Wind damage involved unbonding, creasing, flipping, and displacing shingles from the windward slopes where three second wind gusts ranged from 33 to 43 m/s at 10 m. Laminated type shingles significantly outperformed tab type shingles.
We also will discuss why many shingle roofs have little to no bond. Age, installation, and expansion-contraction effects have resulted in straight-up or diagonal patterns where shingles were not bonded on each directional slope. Such uniform bonding problems have been observed in non-hurricane regions. Thus, it is important for roof inspectors to understand the nature of shingle bonding in order to properly assess wind damage to roof coverings.
Finally, the results of field uplift tests will be presented where bond strength was measured on selected roofs. Once the bond was broken, the tabs were resealed with adhesive then retested to determine the bond strength of the repairs. It was found that resealed shingles had higher bond strengths.
- Document Type: Conference paper
- Document Category: Conference Material
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What's New with the Online Textbook for Tropical Meteorology?
Arlene Laing, UCAR/COMET, Boulder, CO; and J. L. Evans and M. Pope -
The COMET Program (http://www.comet.ucar.edu) is an established leader in providing multimedia education materials with an emphasis on mesoscale processes and phenomena. The rapid evolution of delivery technology for distance learning materials has enabled the COMET Program, under a multi-agency cooperative agreement, to develop cutting edge training in such a way that it not only serves our core sponsors, but also is freely available to both the academic and private sectors via the MetEd Website (http://www.meted.ucar.edu/). MetEd currently has over 550 hours of Web-based training in its continually expanding multimedia library with more than 100,000 registered users (~representing over 200 different countries).
In the past two decades, interest in tropical weather and climate has grown, in part, because of the widespread impact of tropical phenomena such as hurricanes, ENSO, as well as land surface changes. Within this period, our understanding of the tropical atmosphere and its interaction with the ocean and land has expanded greatly. Meanwhile, undergraduate education has been challenged by the lack of an appropriate tropical meteorology textbook that integrates the new knowledge. At the same time, new technology has expanded opportunities for learning. In response to the need, the COMET program launched an online tropical meteorology textbook, Introduction to Tropical Meteorology.
Chapters appear as they are completed at http://www.meted.ucar.edu/tropical/textbook/. This Web-based tropical meteorology textbook covers fundamental science of the tropical atmosphere and synthesizes the tremendous increase in our knowledge of tropical meteorology during the past two decades. Each chapter is reviewed for scientific accuracy and appropriateness of academic level by scientists and professors with expertise in diverse aspects of tropical meteorology.
Completed and anticipated chapter topics for 2010 include, Tropical Remote Sensing Application; Tropical Cyclones; Tropical Variability; Distribution of Moisture and Precipitation; Mesoscale and Local Weather Systems; Global Circulation and the Tropics; Observations, Analysis, and Prediction of Tropical Weather. The latter chapter has a special focus section on the Australian-Indonesian Monsoon as well as interviews with tropical forecasters from the National Hurricane Center in Miami and the Regional Specialized Meteorological Centre in La Réunion.
A variety of methods and strategies are used to teach the content, including graphics and animations, interactive exercises, focus areas, case studies, review questions, and quizzes. Each section of a chapter has links to additional resources that augment the material. The book may be used as a traditional textbook in its printed form while sections of the online version may be used as laboratory exercises or for independent learning. While the book is aimed at undergraduate students who have completed introductory meteorology and who know basic thermodynamic and dynamic meteorology, it is also a resource for early graduate students, professionals, and anyone interested in tropical weather and climate.
by 128.117.110.163 on 12-1-2009—>
- Document Type: Conference paper
- Document Category: Conference Material
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Michael J. Brennan, NOAA/NWS/NHC, Miami, FL; and D. P. Brown, R. Knabb, and M. DeMaria -
The National Hurricane Center (NHC) began issuing intensity probabilities for tropical cyclones (TCs) in the 1990s. The original product used the long-term mean NHC intensity forecast errors and the deterministic NHC intensity forecast to compute the likelihood that a tropical cyclone would fall within certain intensity categories (dissipated, tropical depression, tropical storm, hurricane) and the various categories of the Saffir-Simpson Hurricane Scale at specified forecast times during the next 72 hours. However, these probabilities did not take into account land interaction. In 2008, the NHC and CPHC began computing the intensity probabilities from a set of 1,000 realizations, or alternate tracks and intensities, that vary around the official forecast based on a Monte Carlo sampling of historical errors in the NHC and CPHC track and intensity forecasts. The Monte Carlo technique accounts for land interaction and should provide a more accurate assessment of the chances that the intensity of a tropical cyclone will fall within the various categories. This study provides a verification of Monte Carlo-based intensity probabilities issued by NHC and CPHC with each advisory in the central North Pacific, eastern North Pacific, and Atlantic basins during the 2008 and 2009 hurricane seasons. The probabilities will be verified using the NHC and CPHC best tracks.
The study will also discuss future enhancements to the product, including the computation of intensity probabilities valid at landfall. The current product provides probabilities at specific times during the forecast period. For example, if a storm is near land at a specific time, many of the 1,000 tracks may have already intersected land, which results in weaker storms in those realizations. Because of this, intensity probabilities tend to be spread nearly equally among the various intensity categories when a tropical cyclone is forecast to be near land. To obtain accurate landfall intensity probabilities, a future enhancement will be to produce conditional probabilities using the tracks and intensities of only those realizations that cross the coast between pre-defined points. The intensity of each realization when it crosses the coast between the pre-defined points can be used to create landfall intensity probabilities. This study will provide a summary of the methodology used to produce the landfall intensity probabilities, and will show examples from recent storms of how these probabilities could be used in NHC and CPHC operational products in the future, as well as potential uses for decision makers such as emergency managers.
- Document Type: Conference paper
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Verification of 12 years of NOAA Atlantic seasonal hurricane forecasts
Eric S. Blake, NOAA/NCEP/NHC, Miami, FL; and R. J. Pasch and G. D. Bell -
The NOAA Climate Prediction Center, in coordination with the Hurricane Research Division and the National Hurricane Center, has been making Atlantic seasonal hurricane forecasts since 1998. Although the methodology and tools used to make these forecasts have continued to evolve, it is useful to determine how much skill these forecasts have displayed during the 12-year period. This study will present a verification of the seasonal hurricane forecasts, some of the forecast tools and a comparison with various skill and climatology-based metrics.
- Document Type: Conference paper
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Validation of Vaisala's Global Lightning Dataset (GLD360) over the continental United States
Nicholas W. S. Demetriades, Vaisala, Inc., Tucson, AZ; and M. J. Murphy and J. A. Cramer -
Vaisala’s Global Lightning Dataset (GLD360) was launched in September 2009. GLD360 is the first ground-based lightning detection network capable of providing both worldwide coverage and uniform, high performance without severe detection differences between daytime and nighttime conditions. Expected GLD360 cloud-to-ground (CG) flash detection efficiency is 70% and median CG stroke location accuracy is 5-10 km.
This paper will describe recent cloud-to-ground (CG) flash detection efficiency and stroke location accuracy validation results over the continental United States using Vaisala’s National Lightning Detection Network (NLDN) as ground truth. A companion validation study has been carried out in southeast Brazil. These two studies are the first of many such studies that will be carried out around the globe as GLD360 coverage and performance evolve. Vaisala plans to use these validation studies to continually assess GLD360 performance and address differences between expected and validated performance.
Validation was performed for 22 select days from 1 December 2009 through 31 January 2010 where lightning occurred over both the continental U.S. and southeast Brazil. This ensured GLD360 network operational status was the same for both validation studies.
GLD360 CG flash detection efficiency ranged from 86% to 92% throughout the 24-hour UTC day, with little day/night variation. This variability in detection efficiency as a function of UTC time is much smaller than that observed in other existing long-range lightning detection systems. These results exceed the expected GLD360 70% CG flash detection efficiency over the continental U.S.
GLD360 median location accuracy was 10.8 km for the 770,421 matched GLD360/NLDN CG strokes during December 2009/January 2010 over the continental U.S. These results are slightly poorer than the expected GLD360 5-10 km median CG stroke location accuracy over the continental U.S.
Additional maps will show NLDN CG strokes overlaying GLD360 lightning strokes and GLD360 lightning strokes overlaying GOES-11/GOES-12 infrared satellite imagery. These maps clearly demonstrate that GLD360 highlights the appropriate areas of enhanced convective activity across the continental U.S., North Atlantic, and North Pacific. Some areas around convection show outlier (or scattered) lightning events. These GLD360 outlier lightning events tend to be more numerous in and around high lightning rate storms.
- Document Type: Conference paper
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Vaisala dropsondes: History, status, and applications
Ilkka Ikonen II, Vaisala, Inc., Vantaa, Finland; and N. W. S. Demetriades and R. L. Holle -
Vaisala has been the manufacturer of commercial dropsondes for many years, and was recently awarded a renewed five-year NOAA production contract for model RD94 dropsondes after an open bid process. Vaisala has also acquired the RD94 license from NCAR to provide the dropsonde to users outside the U.S. government. The experience for dropsondes has been gained in part from the design and manufacture of radiosondes since the beginning of Vaisala in the 1930s. Vaisala began co-operation in developing the RD94 with the National Center for Atmospheric Research, NOAA, and the German Aerospace Research Establishment (DLR) in 1994.
The current dropsonde RD94 sends temperature, humidity, pressure and GPS (wind speed and direction) data to the aircraft every 0.5 seconds, and weighs 390 grams. A drop from 20,000 feet (6.1 km) takes seven minutes as it descends while stabilized by parachute, although they can be operated up to an altitude of 24 km in both arctic and tropical environments. Dropsondes can be deployed at indicated airspeeds up to 250 knots.
The data acquisition system on the aircraft, AVAPS (Airborne Vertical Atmospheric Profiling System), collects two independent measurements per second and transmits the data in real time to users. AVAPS handles up to four dropsondes descending simultaneously, and is operated by one person.
The dropsonde is an integral part of the reconnaissance of tropical storms and hurricanes in the Atlantic-Gulf-Caribbean basin area. In addition several thousand Vaisala dropsondes are launched annually from more than eight countries in meteorological research and operational reconnaissance. Dropsonde data assimilated into numerical weather prediction models can lead to significant reductions in the position and intensity errors in model forecasts.
- Document Type: Conference paper
- Document Category: Conference Material
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Munehiko Yamaguchi, Univ. of Miami/RSMAS, Miami, FL -
The characteristics of initial ensemble perturbations around Typhoon Sinlaku (2008) produced by ECMWF, NCEP and JMA ensembles are compared using the THORPEX Interactive Grand Global Ensemble (TIGGE). The dynamical mechanisms of the growth of the advection flow are then compared between the ECMWF and NCEP ensembles. In the comparison, it is found that the vertical and horizontal distributions of initial perturbations as well as the amplitude are quite different among the three NWP centers prior to, during and after the recurvature of Sinlaku. In addition, it turns out that those differences cause a difference in the advection flow not only at the initial time but also during the subsequent forecast period. ECMWF ensembles have shown a relatively large growth of the advection flow, which results from 1) the baroclinic instability in a vortex, 2) the baroclinic instability associated with the mid-latitude waves and 3) the barotropic instability in a vortex. Those features are less distinctive in NCEP ensembles. A statistical verification shows that the ensemble spread of TC track predictions in NCEP (ECMWF) is larger than ECMWF (NCEP) for one (three) day forecasts on average. It can be inferred that while ECMWF starts from relatively small amplitudes of initial perturbations, the growth of the perturbations help to amplify the ensemble spread of tracks. On the other hand, the relatively large amplitudes of initial perturbations seem to play a role in producing the ensemble spread of tracks in NCEP.
- Document Type: Conference paper
- Document Category: Conference Material
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Patrick A. Harr, NPS, Monterey, CA; and E. R. Sanabia and A. B. Penny -
An accurate forecast of many tropical and extratropical factors associated with the extratropical transition (ET) of tropical cyclones remains a challenging problem and was a principal focus area for the THORPEX-Pacific Asian Regional Campaign (T-PARC). In September 2008, Typhoon Sinlaku became an intense tropical cyclone that recurved over Taiwan and moved poleward to pass just south of the primary islands of Japan. Typhoon Sinlaku presented an excellent opportunity to examine predictability issues associated with ET, as there was a large uncertainty in the track at recurvature and there was large variability in predicted downstream development following the ET. The ET of Typhoon Sinlaku was observed by multiple satellite and airborne reconnaissance platforms in support of the T-PARC field program, which provides for a unique opportunity to compare and contrast forecast, analyzed, and observed conditions associated with the character of ET and impacts on the midlatitude circulation into which the decaying tropical cyclone is moving.
Following recurvature over the northern tip of Taiwan, deep convection in TY Sinlaku was severely reduced under the influence of strong vertical wind shear due to the midlatitude westerly winds. However, significant convection developed downshear of the low-level center of the decaying tropical cyclone. The resurgence of deep convection contributed to the re-intensification of TY Sinlaku such that it regained typhoon intensity south of Japan. The re-intensification altered the structure of the typhoon, enabled the onset of ET, and contributed to reduced predictability of the impact of the tropical cyclone on downstream midlatitude circulations.
The post-recurvature fluctuation in intensity and structure of TY Sinlaku prior to ET was not accurately forecast in any of the operational global models that were used during T-PARC (i.e., GFS, NOGAPS, UKMO, ECMWF, JMA), and we hypothesize that this error was directly related to errant track and re-intensification forecasts. In all cases, the reduced predictability was in the sense of over development of significant downstream high-amplitude circulations that propagated to western North America. To more thoroughly understand the mechanism for the deepening, it is necessary to examine the relative role(s) of the typhoon track following recurvature and its relation to the re-intensification stage as the storm passed south of Japan. In several forecast sequences when overdevelopment of downstream development was severe, the forecast track was north of the analyzed track. This track shift influenced the interaction between the decaying typhoon and the midlatitude circulation into which it is moving. The northward shift in the forecast track is examined relative to the forecast storm structure and to factors related to downstream development.
- Document Type: Conference paper
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Jason M. Cordeira, University at Albany/SUNY, Albany, NY -
The goal of this study is to investigate tropical–extratropical interactions occurring on intraseasonal time scales that can significantly influence intraseasonal variability in the Northern Hemisphere (NH) zonal available potential energy (APE) and the “spin-up” of the NH general circulation. The spin-up of the NH general circulation in late 2007 was noteworthy in that the NH zonal APE increased 29% (relative to climatology) between 27 October and 11 November. This period of increasing NH zonal APE coincided with the progression of anomalous tropical convection associated with the Madden–Julian Oscillation (MJO) from the Maritime Continent into the western Pacific Ocean. Subsequently, the NH zonal APE decreased 32% between 15 November and 3 December in conjunction with the tropical and extratropical phases in the life cycles of western North Pacific tropical cyclones (TCs) Mitag, Hagibis, and 26W. This period of decreasing NH zonal APE coincided with the warmest 850-hPa temperature observed in December at Barrow, AK, between 1948 and 2008. The evolution of the tropical and extratropical North Pacific flow during late 2007 represents an extraordinary example of tropical–extratropical interaction on intraseasonal time scales (e.g., one-to-two weeks) that is conducive to intraseasonal variability in the NH zonal APE and to the occurrence of downstream high-impact weather events.
The research to be presented will identify tropical–extratropical interactions that occur in conjunction with climatologically significant periods of intraseasonal variability in the NH zonal APE, and will emphasize the contributions of the MJO and the evolution of western North Pacific TCs to this variability. Preliminary results suggest that the MJO can be associated with an intensification of the North Pacific waveguide and concurrent increases in NH zonal APE, whereas the evolution of western North Pacific TCs can contribute to decreases in NH zonal APE during periods of cyclogenesis, downstream development, and large-scale flow amplification over the eastern North Pacific and North America. As a result, high-impact weather events often are observed in conjunction with intraseasonal variability in the NH zonal APE.
- Document Type: Conference paper
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E.M. Hicks, Université des Antilles et de la Guyane, Pointe à Pitre, Guadeloupe; and C. A. Pontikis, D. Martinez, I. Mitrani, and I. Borrajero -
- Document Type: Conference paper
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