Tuesday, 8 January 2019: 11:45 AM
North 224B (Phoenix Convention Center - West and North Buildings)
Strong midlatitude cyclones exiting the Rocky Mountain region in late winter and early spring are often responsible for disruptive weather across eastern 2/3 of the continental United States (CONUS). Hazardous surface weather in these disturbances ranges from blizzards to severe convection depending upon the location within the large-scale storm circulation. These synoptic disturbances can also provide environments that are conducive to turbulence at commercial aviation cruising altitudes in the upper-troposphere/lower-stratosphere (UTLS). Prediction of UTLS flight-level turbulence in these weather systems is often difficult because of uncertainties regarding precise mechanisms responsible for initiation of the turbulence. In the current presentation we examine high-resolution WRF-model
simulations and assess likely mechanisms responsible for regional clusters of moderate and severe turbulence during a 24-hour period (00 UTC 30 April - 00 UTC 1 May 2017) in which a few hundred pilot reports (PIREPs) of turbulence occurred across the eastern 2/3 of the CONUS. Nested horizontal grids (Fig. 1a) are used to capture both the large synoptic disturbance exiting the Rockies and its associated precipitation pattern (Fig. 1b) with convection-allowing horizontal grid spacings of 3.3 km in d02 and 1.1 km in both d03 and d04, where the most severe turbulence occurs. The model successfully captures a large squall line extending from from the Midwest into the lower Mississippi Valley, which occurs east of the 250-hPa cyclone (Fig. 1b). However, an interesting aspect of this case is that the most severe reported turbulence occurs nearly 1000 km outside of the most deep and intense convection. In particular, one area with severe turbulence is located in clear air in the northwest portion of d04 (Fig. 1a), while a second occurs in d03 (Fig. 1a) in conjuction with a midtropospheric jet and frontal zone with shallower cloudiness (not shown). Results to be presented at the conference
will focus primarily on the likely mechanisms for turbulence occurring in these two regions.
simulations and assess likely mechanisms responsible for regional clusters of moderate and severe turbulence during a 24-hour period (00 UTC 30 April - 00 UTC 1 May 2017) in which a few hundred pilot reports (PIREPs) of turbulence occurred across the eastern 2/3 of the CONUS. Nested horizontal grids (Fig. 1a) are used to capture both the large synoptic disturbance exiting the Rockies and its associated precipitation pattern (Fig. 1b) with convection-allowing horizontal grid spacings of 3.3 km in d02 and 1.1 km in both d03 and d04, where the most severe turbulence occurs. The model successfully captures a large squall line extending from from the Midwest into the lower Mississippi Valley, which occurs east of the 250-hPa cyclone (Fig. 1b). However, an interesting aspect of this case is that the most severe reported turbulence occurs nearly 1000 km outside of the most deep and intense convection. In particular, one area with severe turbulence is located in clear air in the northwest portion of d04 (Fig. 1a), while a second occurs in d03 (Fig. 1a) in conjuction with a midtropospheric jet and frontal zone with shallower cloudiness (not shown). Results to be presented at the conference
will focus primarily on the likely mechanisms for turbulence occurring in these two regions.
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