Convection in future winter storms over northern Europe.

2021 ◽  
Author(s):  
Ségolène Berthou ◽  
Elizabeth Kendon ◽  
Malcolm Roberts ◽  
Benoît Vannière ◽  
Danijel Belušic ◽  
...  
Keyword(s):  
Convective Available Potential Energy ◽  
Conveyor Belt ◽  
Northern Europe ◽  
Intense Rainfall ◽  
Sea Level Pressure ◽  
Winter Storms ◽  
Driving Model ◽  
Convective Inhibition ◽  
Storm Characteristics ◽  
Minimum Sea Level Pressure

<p>Met Office convection-permitting 2.2km simulations over a European domain show 10-20% larger increases in winter mean precipitation at the end of the century compared to their 25km convection-parameterised driving model. We identify individual storms with a maximum vorticity tracking algorithm and look at storm characteristics at their time of deepest minimum sea level pressure. We show that the thermodynamical characteristics of future winter storms are getting closer to present-day autumn storms, with future winter storms showing larger values of convective available potential energy and convective inhibition and more intense rainfall in their warm sector. This suggests that embedded convection in the warm conveyor belt is a good candidate to explain the larger future intensification of rainfall per storm in the 2.2km model compared to the convection-parameterised model. Multi-model analysis is underway to identify whether these conclusions hold in other convection-permitting models.</p>

scholarly journals Brief Communication: An electrifying atmospheric river – understanding the thunderstorm event in Santa Barbara County during March 2019

2020 ◽  
Vol 20 (7) ◽  
pp. 1931-1940
Author(s):  
Deanna Nash ◽  
Leila M. V. Carvalho
Keyword(s):  
Convective Available Potential Energy ◽  
High Water ◽  
Conveyor Belt ◽  
Santa Barbara ◽  
Winter Storms ◽  
Lightning Strikes ◽  
Freezing Level ◽  
Atmospheric River ◽  
The Earth ◽  
Orographic Forcing

Abstract. On 5 March 2019 12:00 UTC, an atmospheric river (AR) made landfall in Santa Barbara, CA, and lasted approximately 30 h. While ARs are typical winter storms in the area, the extraordinary number of lightning strikes observed near coastal Santa Barbara made this event unique. The Earth Networks Global Lightning Network (ENGLN) detected 8811 lightning flashes around southern California (30 to 37∘ N and 130 to 115∘ W) in 24 h, which is roughly 2500 times the climatological flash rate in this region. The AR-related thunderstorm resulted in approximately 23.18 mm accumulated precipitation in 30 h in Santa Barbara. This article examines synoptic and mesoscale features conducive to this electrifying AR event, characterizing its uniqueness in the context of previous March events that made landfall in the region. We show that this AR was characterized by an unusual deep moist layer extending from the low to mid-troposphere in an environment with potential instability and low-elevation freezing level. Despite the negligible convective available potential energy (CAPE) during the peak of the thunderstorm near Santa Barbara, the lifting of layers with high water vapor content in the AR via warm conveyor belt and orographic forcing in a convectively unstable atmosphere resulted in the formation of hail and enhanced electrification.

scholarly journals Analysis of Severe Elevated Thunderstorms over Frontal Surfaces Using DCIN and DCAPE

Atmosphere ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 449
Author(s):  
Patrick Market ◽  
Kevin Grempler ◽  
Paula Sumrall ◽  
Chasity Henson
Keyword(s):  
Weather Prediction ◽  
Convective Available Potential Energy ◽  
Numerical Weather Prediction Model ◽  
Surface Boundary ◽  
Storm Events ◽  
Cold Side ◽  
Severe Thunderstorms ◽  
Stable Surface Layer ◽  
Different Populations ◽  
Convective Inhibition

A 10-year study of elevated severe thunderstorms was performed using The National Centers for Environmental Information Storm Events Database. A total of 80 elevated thunderstorm cases were identified, verified, and divided into “Prolific” and “Marginal” classes. These severe cases occurred at least 80 km away from, and on the cold side of, a surface boundary. The downdraft convective available potential energy (DCAPE), downdraft convective inhibition (DCIN), and their ratio are tools to help estimate the potential for a downdraft to penetrate through the depth of a stable surface layer. The hypothesis is that as the DCIN/DCAPE ratio decreases, there exists enhanced possibility of severe surface winds. Using the initial fields from the Rapid Refresh numerical weather prediction model, datasets of DCIN, DCAPE, and their ratio were created. Mann-Whitney U tests on the Prolific versus Marginal case sets were undertaken to determine if the DCAPE and DCIN values come from different populations for the two different case sets. Results show that the Prolific cases have values of DCIN closer to zero, suggesting the downdraft is able to penetrate to the surface causing severe winds. Thus, comparing DCIN and DCAPE is a viable tool in determining if downdrafts will reach the surface from elevated thunderstorms.

scholarly journals WRF Forecasts of Great Plains Nocturnal Low-Level Jet-Driven MCSs. Part II: Differences between Strongly and Weakly Forced Low-Level Jet Environments

2016 ◽  
Vol 31 (5) ◽  
pp. 1491-1510 ◽  
Author(s):  
Brian J. Squitieri ◽  
William A. Gallus
Keyword(s):  
Great Plains ◽  
Convective Available Potential Energy ◽  
Initiation Time ◽  
Mixing Ratio ◽  
Atmospheric Water ◽  
Low Level ◽  
The North ◽  
Low Level Jet ◽  
Convective Inhibition ◽  
Water Vapor Mixing Ratio

Abstract The classic Great Plains southerly low-level jet (LLJ) is a primary factor in sustaining nocturnal convection. This study compares convection-allowing WRF forecasts of LLJ events associated with MCSs in strongly and weakly forced synoptic environments. The depth of the LLJs and magnitude, altitude, and times of the LLJ peak wind were evaluated in observations and WRF forecasts for 31 cases as well as for case subsets of strongly and weakly forced synoptic regimes. LLJs in strongly forced regimes were stronger, deeper, and peaked at higher altitudes and at earlier times compared to weakly forced cases. Mean error MCS-centered composites of WRF forecasts versus RUC analyses were derived at MCS initiation time for the LLJ atmospheric water vapor mixing ratio, LLJ total wind magnitude, convergence, most unstable convective available potential energy (MUCAPE), and most unstable convective inhibition (MUCIN). In most configurations, simulated MCSs in strongly and weakly forced regimes initiated to the north and east of observations, generally in a region where LLJ moisture, MUCAPE, and MUCIN fields were forecast well, with larger errors outside this region. However, WSM6 simulations for strongly forced cases showed a southward displacement in MCS initiation, where a combination of ambient environmental factors and microphysics impacts may simultaneously play a role in the location of forecast MCS initiation. Strongly forced observed and simulated MCSs initiated west of the LLJ axis and moved eastward into the LLJ, while observed and simulated MCSs in weakly forced environments traversed the termini of the LLJ. A northward bias existed for simulated MCS initiation and LLJ termini for weakly forced regimes.

scholarly journals Should Reversible Convective Inhibition be Used when Determining the Inflow Layer of a Convective Storm?

2021 ◽  
Vol 78 (10) ◽  
pp. 3047-3067
Author(s):  
Shawn S. Murdzek ◽  
Paul M. Markowski ◽  
Yvette P. Richardson ◽  
Matthew R. Kumjian
Keyword(s):  
Potential Energy ◽  
Convective Available Potential Energy ◽  
Adiabatic Process ◽  
Convective Storm ◽  
Available Potential Energy ◽  
Convective Inhibition

AbstractConvective inhibition (CIN) is one of the parameters used by forecasters to determine the inflow layer of a convective storm, but little work has examined the best way to compute CIN. One decision that must be made is whether to lift parcels following a pseudoadiabat (removing hydrometeors as the parcel ascends) or reversible moist adiabat (retaining hydrometeors). To determine which option is best, idealized simulations of ordinary convection are examined using a variety of base states with different reversible CIN values for parcels originating in the lowest 500 m. Parcel trajectories suggest that ascent over the lowest few kilometers, where CIN is typically accumulated, is best conceptualized as a reversible moist adiabatic process instead of a pseudoadiabatic process. Most inflow layers do not contain parcels with substantial reversible CIN, despite these parcels possessing ample convective available potential energy and minimal pseudoadiabatic CIN. If a stronger initiation method is used, or hydrometeor loading is ignored, simulations can ingest more parcels with large amounts of reversible CIN. These results suggest that reversible CIN, not pseudoadiabatic CIN, is the physically relevant way to compute CIN and that forecasters may benefit from examining reversible CIN instead of pseudoadiabatic CIN when determining the inflow layer.

scholarly journals A 142-Year Climatology of Northern California Landslides and Atmospheric Rivers

2019 ◽  
Vol 100 (8) ◽  
pp. 1499-1509 ◽  
Author(s):  
Jason M. Cordeira ◽  
Jonathan Stock ◽  
Michael D. Dettinger ◽  
Allison M. Young ◽  
Julie F. Kalansky ◽  
...  
Keyword(s):  
Water Vapor ◽  
San Francisco ◽  
San Francisco Bay ◽  
San Francisco Bay Area ◽  
Water Vapor Transport ◽  
Atmospheric Conditions ◽  
Sea Level Pressure ◽  
Winter Storms ◽  
Atmospheric Rivers ◽  
Bay Area

AbstractWe compare a novel dataset of San Francisco Bay Area landslides from 1871 to 2012 to corresponding atmospheric conditions commonly associated with Pacific winter storms and landfalling atmospheric rivers (ARs). Landslides in the San Francisco Bay Area occur primarily during winter months, coinciding with enhanced integrated water vapor transport (IVT) magnitudes ≥250 kg m–1 s–1 at the coast 76% of the time and with landfalling ARs over the near-offshore northeast Pacific 82% of the time. Results illustrate that days, or the first in a series of days, with a landslide (i.e., landslide onset days) typically occur in association with NOAA Twentieth Century Reanalysis–derived IVT magnitudes ≥250 kg m–1 s–1 that persist for ∼20 h and temporal maxima in precipitation rates. Composite analyses of sea level pressure, integrated water vapor, and IVT during 3-month periods during September–May on landslide onset days further illustrate that these events coincide with regions of low pressure to the northwest of California and high pressure to the south, synoptic-scale flow conditions associated with strong onshore flow, and water vapor transports in the form of landfalling ARs.

Impact of CYGNSS-derived winds on tropical cyclone forecasts in a global and regional model

2021 ◽  
Author(s):  
Michael J. Mueller ◽  
Bachir Annane ◽  
S. Mark Leidner ◽  
Lidia Cucurull
Keyword(s):  
Tropical Cyclone ◽  
Regional Model ◽  
Global Model ◽  
Lead Times ◽  
Rapid Intensification ◽  
Lateral Boundary ◽  
Sea Level Pressure ◽  
The Impact ◽  
Vector Wind ◽  
Minimum Sea Level Pressure

AbstractAn observing system experiment (OSE) was conducted to assess the impact of wind products derived from the Cyclone Global Navigation Satellite System (CYGNSS) on tropical cyclone (TC) track, maximum 10-m wind speed (Vmax), and minimum sea level pressure forecasts. The experiment used a global data assimilation and forecast system and the impact of both CYGNSS-derived scalar and vector wind retrievals was investigated. The CYGNSS-derived vector wind products were generated by optimally combining the scalar winds and a gridded a priori vector field. Additional tests investigated the impact of CYGNSS data on a regional model through the impact of lateral boundary and initial conditions from the global model during the developmental phase of Hurricane Michael (2018).In the global model, statistically significant track forecast improvements of 20-40 km were found in the first 60 h. Vmax forecasts showed some significant degradations of ~2 kts at a few lead times, especially in the first 24 h. At most lead times, impacts were not statistically significant. Degradations in Vmax for Hurricane Michael in the global model were largely attributable to a failure of the CYGNSS-derived scalar wind test to produce rapid intensification in the forecast failure of the CYGNSS-derived scalar wind test to produce rapid intensification in the forecast symmetrical compared to the control and CYGNSS-derived vector wind test. The regional model used initial and lateral boundary conditions from the global control and CYGNSS scalar wind tests. The regional forecasts showed large improvements in track, Vmax, and minimum sea level pressure.

scholarly journals Climatology and Changes of Extratropical Cyclone Activity: Comparison of ERA-40 with NCEP–NCAR Reanalysis for 1958–2001

2006 ◽  
Vol 19 (13) ◽  
pp. 3145-3166 ◽  
Author(s):  
Xiaolan L. Wang ◽  
Val R. Swail ◽  
Francis W. Zwiers
Keyword(s):  
North Atlantic ◽  
Storm Track ◽  
Northern Europe ◽  
Cyclone Activity ◽  
Historical Trends ◽  
Sea Level Pressure ◽  
The North ◽  
Abrupt Changes ◽  
Increasing Trend ◽  
Activity Comparison

Abstract In this study, a cyclone detection/tracking algorithm was used to identify cyclones from two gridded 6-hourly mean sea level pressure datasets: the 40-yr ECMWF Re-Analysis (ERA-40) and the NCEP–NCAR reanalysis (NNR) for 1958–2001. The cyclone activity climatology and changes inferred from the two reanalyses are intercompared. The cyclone climatologies and trends are found to be in reasonably good agreement with each other over northern Europe and eastern North America, while ERA-40 shows systematically stronger cyclone activity over the boreal extratropical oceans than does NNR. However, significant differences between ERA-40 and NNR are seen over the austral extratropics. In particular, ERA-40 shows significantly greater strong-cyclone activity and less weak-cyclone activity over all oceanic areas south of 40°S in all seasons, while it shows significantly stronger cyclone activity over most areas of the austral subtropics in the warm seasons. The most notable historical trends in cyclone activity are found to be associated with strong-cyclone activity. Over the boreal extratropics, both ERA-40 and NNR show a significant increasing trend in January–March (JFM) strong-cyclone activity over the high-latitude North Atlantic and over the midlatitude North Pacific, with a significant decreasing trend over the midlatitude North Atlantic and a small increasing trend over northern Europe. The JFM changes over the North Atlantic are associated with the mean position of the storm track shifting about 181 km northward. Importantly, there is no evidence of abrupt changes identified for the boreal extratropics, although previous studies have suggested that the upward trend found in the NNR data could be biased high. However, there exist a few abrupt changes over the austral extratropics, which appear to be attributable to the increasing availability of observations assimilated in the reanalyses. After diminishing the effects of these abrupt changes, strong-cyclone activity over the austral circumpolar oceanic region is identified to have an increasing trend in October–December (OND) and July–September (JAS), with a decreasing trend over the 40°–60°S zone in JAS.

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