Hydrometeorological analysis and forecasting of a 3 d flash-flood-triggering desert rainstorm

Rinat, Yair; Marra, Francesco; Armon, Moshe; Metzger, Asher; Levi, Yoav; Khain, Pavel; Vadislavsky, Elyakom; Rosensaft, Marcelo; Morin, Efrat

doi:10.5194/nhess-21-917-2021

Cited by 23 publications

(22 citation statements)

References 109 publications

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“…Owing to the small spatiotemporal scales of precipitation patterns and their effects on the ground, documenting the local impact of heavy precipitation requires high-resolution observations from weather radars, satellites and cellular links to complement in-situ measurements, as well as post-event surveys (Messer et al, 2006;Morin et al, 2007;Koutroulis and Tsanis, 2010;Miglietta et al, 2013;Amponsah et al, 2018;Rinat et al, 2018;Borga et al, 2019;Diakakis et al, 2019;Varlas et al, 2019;Laviola et al, 2020;Rinat et al, 2021). Atmospheric indices can sometimes provide valuable information at the regional scale (Morsy et al, 2020), but effective forecasting of local impacts is still challenging due to the small scales and short response times of the basins (Collier, 2007;Morin et al, 2009;Borga et al, 2014;Zoccatelli et al, 2020).…”

Section: Societal Impactmentioning

confidence: 99%

ESD Reviews: Extreme Weather and Societal Impacts in the Eastern Mediterranean

Hochman

Marra

Messori

et al. 2021

Preprint

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Abstract. Gaining a holistic understanding of extreme weather, from its physical drivers to its impacts on society and ecosystems, is key to supporting future risk reduction and preparedness measures. Here, we provide an overview of the state-of-the-art, knowledge gaps and key open questions in the study of extreme weather events over the vulnerable eastern Mediterranean. This region is situated in a transition zone between subtropical and mid-latitude climates. Extreme weather is mainly governed by the large-scale atmospheric circulation and its interaction with regional synoptic systems, i.e., Cyprus Lows, Red Sea Troughs, Persian Troughs, ‘Sharav’ Lows, and high-pressure systems. Complex orographic features further play an important role in the generation of extreme weather. Most extreme weather events, including heavy precipitation, cold spells, floods and wind storms, are associated with a Cyprus Low or Active Red Sea Trough, whereas heat waves are related with either the Persian Trough and Sub-Tropical High-pressure systems in summer, or the ‘Sharav’ Low during spring time. Heat waves and droughts are projected to significantly increase in both frequency and intensity. In future decades, changes in heavy precipitation frequency and intensity may vary in sign and magnitude depending on the scale, severity and region of interest. There are still relatively large uncertainties concerning the physical understanding and the projected changes of cold spells, wind storms and compound events, as these types of events received comparatively little attention in the literature. We further identify knowledge gaps that relate to the societal impacts of extreme weather. These gaps mainly relate to the effects extreme weather may have on mortality, morbidity and infrastructure in the eastern Mediterranean. Research is currently limited in this context, and we call to strengthen the database of analyzed case-studies. We trust that this can only be suitably accomplished by inter-disciplinary and international regional collaborations, in spite of political unrest.

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Section: Societal Impactmentioning

confidence: 99%

ESD Reviews: Extreme Weather and Societal Impacts in the Eastern Mediterranean

Hochman

Marra

Messori

et al. 2021

Preprint

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“…The factor separation approach [3,40,41] was used to compare the relative impacts of local versus non-local moisture sources. Factor separation was recently used by Lynn et al [42] to decipher the relative importance of desert dust and urban aerosols in the 4 January 2020 flood disaster in Tel Aviv.…”

Section: Factor Separationmentioning

confidence: 99%

“…To put the event in a meteorological context, we note that on 25-27 April 2018, an extreme precipitation event occurred in the Levant. Precipitation intensities with a return period of 75 to 100 years resulted in flash floods of a high magnitude (with a return period of 10 to 50 years), claiming 46 casualties in Israel and Jordan [3]. Such thunderstorms occurred in response to the passage of a very cold upper low-pressure system transversing Egypt, Israel, and Jordan, which provided support for Red-Sea surface trough development, a synoptic-scale weather system known to produce a prolific amount of lightning [4].…”

Section: Introductionmentioning

confidence: 99%

“…As the storm shifted northeastwards towards Iraq, moisture sources from the east and the Mediterranean Sea could have led to a convergence zone over the Jerusalem central mountains. Yet, while forecasters realized that the synoptic situation might produce floods and issued general flood warnings, high-resolution forecasts provided by the Israel Meteorological Service did not predict the intensity of rain and lightning in the Jerusalem area or the actual deadly floods that occurred in the vicinity of the Tzafit gorge basin [3]. For this reason, it was hypothesized that discrepancies in forecast model initial conditionsparticularly atmospheric humidity-might have contributed to model forecast errors.…”

Section: Introductionmentioning

confidence: 99%

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Impacts of Non-Local versus Local Moisture Sources on a Heavy (and Deadly) Rain Event in Israel

et al. 2021

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Motivated by poor forecasting of a deadly convective event within the Levant, the factor separation technique was used to investigate the impact of non-local versus local moisture sources on simulated precipitation and lightning rates in central and southern Israel on 25 and 26 April 2018. Both days saw unusually heavy rains, and it was hypothesized that antecedent precipitation on 25 April contributed to the development of deadly flooding late morning on the 26th, as well as strong lightning and heavy rains later the same day. Antecedent precipitation led to an increase in the precipitable water content and an overall increase in instability as measured by the Convective Available Potential Energy (CAPE). The deadly flood occurred in the area of the Tzafit river gorge (hereafter, Tzafit river), about 25 km southeast of the city of Dimona, a semi-arid region in the northeastern Negev desert. The heavy rains and strong lightning occurred throughout the Levant with local peaks in the vicinity of Jerusalem. Factor separation conducted in model simulations showed that local ground moisture sources had a large impact on the CAPE and subsequent precipitation and lightning rates in the area of Jerusalem, while non-local moisture sources enabled weak convection to occur over broad areas, with particularly strong convection in the area of the Tzafit river. The coupled impact of both moisture sources also led to localized enhanced areas of convective activity. The results suggest that forecast models for the Levant should endeavor to incorporate an accurate depiction of soil moisture to predict convective rain, especially during the typically drier spring-time season.

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“…eumetsat.int/product/EO:EUM:DAT:MSG:HRSEVIRI, last access: 1 June 2019) (Kerkmann, 2019). Air back trajectories for detecting moisture transport were retrieved from the site of the NOAA HYSPLIT model (https://www.ready.noaa.gov/HYSPLIT.php, last access: 1 April 2019) (Rolph et al, 2017).…”

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confidence: 99%

Atmospheric conditions leading to an exceptional fatal flash flood in the Negev Desert, Israel

Dayan

Lensky

Ziv

et al. 2021

Nat. Hazards Earth Syst. Sci.

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Abstract. The study deals with an intense rainstorm that hit the Middle East between 24 and 27 April 2018 and took the lives of 13 people, 10 of them on 26 April during the deadliest flash flood in Tzafit Basin (31.0∘ N, 35.3∘ E), the Negev Desert. The rainfall observed in the southern Negev was comparable to the long-term annual rainfall there, with intensities exceeding a 75-year return period. The timing of the storm, at the end of the rainy season when rain is relatively rare and spotty, raises the question of what the atmospheric conditions were that made this rainstorm one of the most severe late-spring storms. The synoptic background was an upper-level cut-off low that formed south of a blocking high which developed over eastern Europe. The cut-off low entered the Levant near 30∘ N latitude, slowed its movement from ∼10 to <5 m s−1 and so extended the duration of the storm over the region. The dynamic potential of the cut-off low, as estimated by its curvature vorticity, was the largest among the 12 late-spring rainstorms that occurred during the last 33 years. The lower levels were dominated by a cyclone centred over north-western Saudi Arabia, producing north-westerly winds that advected moist air from the Mediterranean inland. During the approach of the storm, the atmosphere over Israel became unstable, with instability indices reaching values favourable for thunderstorms (e.g. CAPE>1500 J kg−1, LI=4 K) and the precipitable water reaching 30 mm. The latter is explained by lower-level moisture advection from the Mediterranean and an additional contribution of mid-level moist air transport entering the region from the east. Three major rain centres were active over Israel during 26 April, only one of them was orographic and the other two were triggered by instability and mesoscale cyclonic centres. The build-up of the instability is explained by a negative upper-level temperature anomaly over the region caused by a northerly flow east of a blocking high that dominated eastern Europe and ground warming during several hours under clear skies. The intensity of this storm is attributed to an amplification of a mid-latitude disturbance which produced a cut-off low with its implied high relative vorticity, low upper-level temperatures and slow progression. All these, combined with the contribution of moisture supply, led to intense moist convection that prevailed over the region for 3 successive days.

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Hydrometeorological analysis and forecasting of a 3 d flash-flood-triggering desert rainstorm

Cited by 23 publications

References 109 publications

ESD Reviews: Extreme Weather and Societal Impacts in the Eastern Mediterranean

ESD Reviews: Extreme Weather and Societal Impacts in the Eastern Mediterranean

Impacts of Non-Local versus Local Moisture Sources on a Heavy (and Deadly) Rain Event in Israel

Atmospheric conditions leading to an exceptional fatal flash flood in the Negev Desert, Israel

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