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Clifford F. Mass

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Clifford F. Mass
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Clifford F. Mass

This paper describes the current application of compact discs (CD-ROM) to the storage and distribution of datasets for atmospheric sciences and related disciplines. CD-ROM technology is reviewed, currently available discs are listed, and a look at future developments is provided.

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Clifford F. Mass

For over a half-century, the Bergen School conceptual model of cyclone structure and development has dominated the practice of synoptic meteorology, especially regarding the techniques by which surface synoptic charts are analyzed. Although the Norwegian paradigm captures some of the essential features of cyclone evolution, research and practical application over the last 60-odd years have revealed significant deficiencies, several of which are discussed in this paper. The Bergen model has also been applied in regions and under conditions quite unlike those for which the model was originally developed. Knowledge of these problems by many in the research and operational communities has had little impact on the manner in which synoptic charts are analyzed or the way the subject is described in many textbooks. Deficiencies in the underlying conceptual model of cyclone development have been compounded by a lack of consistent and well-defined procedures for defining fronts and for analyzing surface synoptic charts. Several examples of confusing and inconsistent surface analyses are presented in this paper.

To resolve these problems, the meteorological community should follow a two-pronged approach. First, the research and operational insights gained over the last half-century should be combined with recent numerical modeling and observational studies to establish improved conceptual models of cyclone evolution. Second, a clear and consistent methodology for analyzing synoptic charts should be devised. Several possible approaches for implementing these suggestions are presented in this paper.

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Clifford F. Mass
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Clifford F. Mass

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The coastal regions of southern Oregon and northern California can be considerably warmer than locations to the north and south when air descends the substantial mountain barrier to the east. This paper describes the event of 27 February 1985, during which Brookings, Oregon experienced the highest February temperature ever observed in that state.

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Clifford F. Mass
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Callie McNicholas and Clifford F. Mass

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Over a half-billion smartphones are now capable of measuring atmospheric pressure, potentially providing a global surface observing network of unprecedented density and coverage. An earlier study by the authors described an Android app, uWx, that served as a test bed for advanced quality control and bias correction strategies. To evaluate the utility and quality of the resulting smartphone pressure observations, ensemble data assimilation experiments were performed for two case studies over the Pacific Northwest. In both case studies, smartphone pressures improved the analyses and forecasts of assimilated and nonassimilated variables. In case I, which considered the passage of a front across the region, cycled smartphone pressure assimilation consistently improved 1-h forecasts of the altimeter setting, 2-m temperature, and 2-m dewpoint. During a postfrontal period, cycled smartphone pressure assimilation improved mesoscale forecasts of hourly precipitation accumulation. In case II, which considered a major coastal windstorm, cycling experiments assimilating smartphone pressures improved 10-m wind forecasts as well as the predicted track and intensity. For both cases, free-forecast experiments initialized with smartphone data produced forecast improvements extending several hours, suggesting the utility of crowdsourced smartphone pressures for short-term numerical weather prediction.

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Clifford F. Mass and David Ovens

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The Camp Fire event was associated with dry, northeasterly winds that descended the western slopes of the Sierra Nevada of Northern California during the early morning hours of 8 November 2018. The downslope winds peaked around sunrise, with strong winds pushing the fire rapidly toward Paradise, California. Similar to recent central/Northern California wildfires associated with downslope winds, the synoptic pattern was characterized by building sea level pressure over the Intermountain West and a trough along the coastal zone, with both the synoptic evolution and low-level winds skillfully forecast by operational models. The maximum wind gusts along the western Sierra Nevada slopes ranged from 10–20 kt (1 kt ≈ 0.51 m s−1) at sheltered locations to 50–60 kt at exposed sites on the mid- to upper slopes of the barrier. The highest winds were not climatologically exceptional, and low-level temperatures were cooler than normal over and to the east of the Sierra Nevada, near normal over the western slopes, and warmer than normal over coastal California. Drier-than-normal conditions prevailed during the ∼3 days preceding and during the event, as a result of downslope winds. The origin of the fire can be traced to strong winds interacting with a failing electrical transmission infrastructure, with highly flammable surface fuels fostering rapid fire movement between the ignition source and Paradise.

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Robert Conrick and Clifford F. Mass

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This study evaluates moist physics in the Weather Research and Forecasting (WRF) Model using observations collected during the Olympic Mountains Experiment (OLYMPEX) field campaign by the Global Precipitation Measurement (GPM) satellite, including data from the GPM Microwave Imager (GMI) and Dual-Frequency Precipitation Radar (DPR) instruments. Even though WRF using Thompson et al. microphysics was able to realistically simulate water vapor concentrations approaching the barrier, there was underprediction of cloud water content and rain rates offshore and over western slopes of terrain. We showed that underprediction of rain rate occurred when cloud water was underpredicted, establishing a connection between cloud water and rain-rate deficits. Evaluations of vertical hydrometeor mixing ratio profiles indicated that WRF produced too little cloud water and rainwater content, particularly below 2.5 km, with excessive snow above this altitude. Simulated mixing ratio profiles were less influenced by coastal proximity or midlatitude storm sector than were GMI profiles. Evaluations of different synoptic storm sectors suggested that postfrontal storm sectors were simulated most realistically, while warm sectors had the largest errors. DPR observations confirm the underprediction of rain rates noted by GMI, with no dependence on whether rain occurs over land or water. Finally, WRF underpredicted radar reflectivity below 2 km and overpredicted above 2 km, consistent with GMI vertical mixing ratio profiles.

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