Vertical Structure of Thunderstorm Outflows

Goff, R. Craig

doi:10.1175/1520-0493(1976)104<1429:vsoto>2.0.co;2

Cited by 315 publications

(55 citation statements)

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“…Cold, dense surface outflows (also referred to as cold pools, gravity currents, or density currents) associated with evaporative cooling of air by precipitation have been studied in a wide variety of storm settings (Wilson and Schreiber 1986;Charba 1974;Engerer 2008;Goff 1976;Wakimoto 1982;Droegemeier and Wilhelmson 1987;Houze 1977;Gamache and Houze 1982;Zipser 1977; and many others). While density currents associated with deep, mixed phase-clouds have been studied extensively for decades, it is only relatively recently that such outflows were found to occur below shallow marine clouds.…”

Section: Discussionmentioning

confidence: 99%

“…Evaporative cooling of precipitation has been known for some time to generate downdrafts and subsequent outflows (Srivastava 1987). Outflows generated by deep convection have been the subject of numerous studies, particularly in mid-latitude continental environments (Wilson and Schreiber 1986;Charba 1974;Engerer 2008;Goff 1976;Wakimoto 1982;Droegemeier and Wilhelmson 1987;Mahoney 1988; and many others). The phenomenon is also described in studies of deep convection over tropical oceans (Houze 1977;Gamache and Houze 1982;Zipser 1977; and many others).…”

Section: Introductionmentioning

confidence: 99%

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Near-Surface Density Currents Observed in the Southeast Pacific Stratocumulus-Topped Marine Boundary Layer*

Wilbanks

Yuter

Szoeke

et al. 2015

Monthly Weather Review

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Density currents (i.e., cold pools or outflows) beneath marine stratocumulus clouds are characterized using 30 days of ship-based observations obtained during the 2008 Variability of American Monsoon Systems (VAMOS) Ocean–Cloud–Atmosphere–Land Study Regional Experiment (VOCALS-REx) in the southeast Pacific. An air density increase criterion applied to the Improved Meteorological (IMET) sensor data identified 71 density current front, core (peak density), and tail (dissipating) zones. The similarity in speeds of the mean density current propagation speed (1.8 m s−1) and the mean cloud-level advection relative to the surface layer wind (1.9 m s−1) allowed drizzle cells to deposit elongated density currents in their wakes. Scanning Doppler lidar captured prefrontal updrafts with a mean intensity of 0.91 m s−1 and an average vertical extent of 800 m. Updrafts were often surmounted by low-lying shelf clouds not connected to the overlying stratocumulus cloud. The observed density currents were 5–10 times thinner and weaker than typical continental thunderstorm cold pools. Nearly 90% of density currents were identified when C-band radar estimated areal average rain rates exceeded 1 mm day−1 over a 30-km diameter. Rather than peaking when rain rates were highest overnight, density current occurrence peaks between 0600 and 0800 local solar time when enhanced local drizzle co-occurred with shallow subcloud dry and stable layers. The dry layers may have contributed to density current formation by enhancing subcloud evaporation of drizzle. Density currents preferentially occurred in a large region of predominantly open cells but also occurred in regions of closed cells.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Near-Surface Density Currents Observed in the Southeast Pacific Stratocumulus-Topped Marine Boundary Layer*

Wilbanks

Yuter

Szoeke

et al. 2015

Monthly Weather Review

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“…The value of k is uncertain and other numbers were proposed, too [50,51]. Solving Equation 4 [42] were also reported by Goff [53] and Mueller and Carbone [44].…”

Section: Lidar Gust Front Detection and Analysismentioning

confidence: 96%

“…Further partial reconstruction of this event is possible by applying various relationships between the height of cold inflow (d) and other features of the gust front. According to several studies that investigated gust fronts at full scale or using physical experiments and numerical simulations (e.g., Reference [42,43,45,53]), the height of the leading edge (H; called gust front head) is usually H 2d. This relationship enables us to further sketch the likely shape of the gust front that occurred over the sea approximately 15 min before the bridge collapse ( Figure 15).…”

Section: Lidar Gust Front Detection and Analysismentioning

confidence: 99%

Investigation of the Weather Conditions During the Collapse of the Morandi Bridge in Genoa on 14 August 2018 Using Field Observations and WRF Model

et al. 2020

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On 14 August 2018, Morandi Bridge in Genoa, Italy, collapsed to the ground that was 40 m below. This tragedy killed 43 people. Preliminary investigations indicated poor design, questionable building practices, and insufficient maintenance—or a combination of these factors—as a possible cause of the collapse. However, around the collapse time, a thunderstorm associated with strong winds, lightning, and rain also developed over the city. While it is unclear if this thunderstorm played a role in the collapse, the present study examines the weather conditions before and during the bridge collapse. The study particularly focuses on the analysis of a downburst that was observed around the collapse time and a few kilometers away from the bridge. Direct and remote sensing measurements are used to describe the evolution of the thunderstorm during its approached from the sea to the city. The Doppler lidar measurements allowed the reconstruction of the gust front shape and the evaluation of its displacement velocity of 6.6 m s−1 towards the lidar. The Weather Research and Forecasting simulations highlighted that it is still challenging to forecast localized thunderstorms with operational setups. The study has shown that assimilation of radar reflectivity improves the timing and reconstruction of the gust front observed by local measurements.

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“…For example, Mass and Ferber (1990) find pressure perturbations of up to 10 hPa in association with flow around an isolated topographical barrier. Localized pressure perturbations on the order of 2-5 hPa have been reported in association with strong frontal passages and in convective cold pools (Goff 1976;Engerer et al 2008). Wheatley and Stensrud (2010) show that assimilating surface pressure observations and, to some extent, 1-h surface pressure tendency observations, increases the accuracy of modeled convective cold pools.…”

Section: Introductionmentioning

confidence: 99%

Utility of Dense Pressure Observations for Improving Mesoscale Analyses and Forecasts

Madaus

Hakim

Mass

2014

Monthly Weather Review

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The use of dense pressure observations is investigated for creating mesoscale ensemble analyses and improving short-term mesoscale forecasts. By exploiting additional observation platforms, the number of pressure observations over the Pacific Northwest region is increased by an order of magnitude over standard airport observations. Quality control and bias correction methods for these observations are discussed, including the use of pressure tendency as an alternative observation type with fewer bias concerns. The enhanced station density provided by these observations contributes to localized adjustments for a variety of mesoscale phenomena. These adjusted analyses yield improved forecasts, including more accurate forecasts of frontal passages and convective bands. Assimilating dense 3-h pressure tendency observations also reduces the error in some forecast surface fields similarly to raw pressure observations, suggesting further investigation into pressure tendency as a mesoscale observation type.

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Vertical Structure of Thunderstorm Outflows

Cited by 315 publications

References 0 publications

Near-Surface Density Currents Observed in the Southeast Pacific Stratocumulus-Topped Marine Boundary Layer*

Near-Surface Density Currents Observed in the Southeast Pacific Stratocumulus-Topped Marine Boundary Layer*

Investigation of the Weather Conditions During the Collapse of the Morandi Bridge in Genoa on 14 August 2018 Using Field Observations and WRF Model

Utility of Dense Pressure Observations for Improving Mesoscale Analyses and Forecasts

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