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Amin Dezfuli

in a southwesterly–westerly direction. Its IVT exceeded 350 kg m –1 s –1 over northeastern Africa and remained high as it continued propagating southwesterly toward Iran. NASA satellite observations detected the maximum rainfall over the western half of Iran, where AR Dena hit the Zagros Mountains ( Fig. 3c ). The moisture laden air cools as it flows upslope due to orographic forcing, and the associated microphysical growth processes produce or strengthen the clouds ( Houze 2012 ). As a result

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James R. Campbell, David A. Peterson, Jared W. Marquis, Gilberto J. Fochesatto, Mark A. Vaughan, Sebastian A. Stewart, Jason L. Tackett, Simone Lolli, Jasper R. Lewis, Mayra I. Oyola, and Ellsworth J. Welton

last tropospheric cloud mechanism contributing to the large-scale exchange of the terrestrial water cycle. Accordingly, cirrus clouds are observed globally at all times of the year, exhibiting an instantaneous global occurrence rate near 40%. Radiatively, however, they are even more distinct. During daylight hours, cirrus are the only cloud genus that can induce either a positive or negative top-of-the-atmosphere forcing (i.e., heating or cooling; all other clouds induce a cooling sunlit effect

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Thomas Jones, Patrick Skinner, Nusrat Yussouf, Kent Knopfmeier, Anthony Reinhart, and David Dowell

W o F SYSTEM AND TC OVERVIEWS. Initial Warn-on-Forecast (WoF) systems have been designed for the prediction of convection driven by overland synoptic and mesoscale forcing; however, the overall concept is also applicable to landfalling tropical cyclones (TCs). The WoF system known as the National Severe Storms Laboratory (NSSL) Experimental Warn-on-Forecast System for Ensembles (NEWS-e) was tested retrospectively during the landfalling phases of Hurricanes Irma and Harvey and used to generate

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Yanluan Lin, Yuanlong Li, Qingshan Li, Minyan Chen, Fanghua Xu, Yuqing Wang, and Bin Huang

of free convection at about 1,450 m. Although convection and precipitation might have reduced the CAPE at 1200 UTC, it is very difficult to generate and sustain such strong convection and updrafts solely by the release of CAPE. This is part of the reason why we think there are other types of forcing, possibly wave forcing and frictional contrast across the coastline as well, rather than thermodynamic instability alone, for this band. Fig . 4. Skew T –log p diagram at Fuzhou at (a) 0000 and (b

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Joseph C. Picca, David M. Schultz, Brian A. Colle, Sara Ganetis, David R. Novak, and Matthew J. Sienkiewicz

The northeast U.S. extratropical cyclone of 8–9 February 2013 resulted in a blizzard that produced more than 0.9 m (3 ft) of snow in central Connecticut and more than 0.6 m (2 ft) across portions of Long Island ( Fig. 1 ). Hurricane-force winds battered the coast from Massachusetts to Maine. On Long Island, a rapid transition from rain to snow, with subsequent extreme snowfall rates of 7.5–10 cm h −1 (3–4 in h −1 ), occurred during the evening rush hour, stranding hundreds of cars on major

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Clifford F. Mass, Robert Conrick, Nicholas Weber, and Joseph P. Zagrodnik

. Photographs by Olympic National Park personnel and others showed numerous treefalls, documenting both the large size of some of the fallen trees and the extraordinary force required to damage them ( Fig. 2 ). Fig . 1. (a) View of the regional geography, with a red star indicating the location of the downed trees. (b) A closer view showing Lake Quinault, the surrounding terrain, and ground sites referenced in this study. The Forks profiler and Quillayute radiosonde sites are also shown in (a). Fig . 2

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Peter Stucki, Stefan Brönnimann, Olivia Martius, Christoph Welker, Ralph Rickli, Silke Dierer, David N. Bresch, Gilbert P. Compo, and Prashant D. Sardeshmukh

per day. Figure 1a shows hurricane-force winds on Saentis summit in northeastern Switzerland at 0600 LT (0500 UTC) on 15 February 1925. Gale-force winds were observed in southern to southwestern Switzerland, and strong winds were observed at three stations near Altdorf, all located in a typical foehn valley in central Switzerland. At 1200 LT (1100 UTC), winds increased markedly in Zurich, while weaker winds were observed around Altdorf (not shown). Meteorologists of the time appreciated the

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K. Lagouvardos, V. Kotroni, T. M. Giannaros, and S. Dafis

around 15–16 m s −1 over the area of the wildfire (denoted by the rectangle in Fig. 5 ). The model results shown in Fig. 5 clearly highlight the occurrence of the combination of high temperature, low relative humidity, and almost gale-force winds, conditions that set the stage for the rapid spread of the wildfire. A west–east cross section, following the thick line depicted in Fig. 5 , is shown in Fig. 6 . The cross section was drawn over the southern flanks of Mt. Penteli and crosses the

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F. M. Ralph and M. D. Dettinger

midlatitudes. They are thousands of kilometers long and, on average, only 400 km wide; 75% of the water vapor transport occurs below 2.25-km altitude. ARs produce extreme precipitation in coastal regions because they transport large quantities of water vapor and comprise almost ideal conditions for producing heavy orographic rains and flooding when they encounter mountains. Although the dominant precipitation forcing mechanism in the majority of West Coast extreme precipitation events is orographic lifting

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Alan Gerard, Steven M. Martinaitis, Jonathan J. Gourley, Kenneth W. Howard, and Jian Zhang

of 1 km ( Gourley et al. 2017 ). This study utilized the MRMS DP QPEs as forcing into the various FLASH products. Analyses from the Hydrometeorology Testbed—MRMS Hydro (HMT-Hydro; Martinaitis et al. 2017 ) experiment and feedback from local NWS offices identified three FLASH products that were most useful for the prediction and warning of flash floods: Unit streamflow from the Coupled Routing and Excess Storage Model (CREST; Wang et al. 2011 ) depicts the discharge of surface water normalized

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