scholarly journals SIMULAÇÃO NUMÉRICA DE DOIS SISTEMAS CONVECTIVOS DE MESOESCALA UTILIZANDO O MODELO WRF

2016 ◽  
Vol 38 (2) ◽  
pp. 1102
Author(s):  
Kauan Vargas Casarin
Keyword(s):  
Linear Case ◽  
Weather Research And Forecasting ◽  
Climate Forecast System Reanalysis ◽  
Convective Systems ◽  
The North ◽  
Entire Duration ◽  
Circular Case ◽  
Mesoscale Convective ◽  
The Moment ◽  
Different Characteristics

The model Weather Research and Forecasting (WRF) was used in order to simulate two Mesoscale Convective Systems (MCSs) with different characteristics in order to analyze how variables such as wind directional shear and  thickness gradient are modified within the MCSs along its entire duration. The first event is a linear MCS that extended from the north of Argentina to the South Atlantic in November 30, 2009 and the second is a circular MCS or MCC (mesoscale convective complex) that occurred on the RS and Uruguay on November 18, 2009. The two systems were identified through images of the satellite GOES (Geostationary Operational Environmental Satellite) using an automatic tracking of MCSs and for the simulation of events in WRF we used the data reanalysis of CFSR (Climate Forecast System Reanalysis). The simulation results indicated that the rate of reduction thickness gradient is greater in the circular case than in the linear case and at the time that events are initiated the wind directional shear is higher in the linear case but he reduces until the moment of dissipation of the MCS different than occurs in MCC, which has an increased wind directional shear when the system is almost dissipating.

Numerical Investigations on the Formation of Tropical Storm Debby during NAMMA-06

2010 ◽  
Vol 25 (3) ◽  
pp. 866-884 ◽  
Author(s):  
Sen Chiao ◽  
Gregory S. Jenkins
Keyword(s):  
Mesoscale Model ◽  
Vortex Formation ◽  
Tropical Storm ◽  
Mesoscale Convective Systems ◽  
Weather Research And Forecasting ◽  
Grid Spacing ◽  
Convective Systems ◽  
Sensitivity Tests ◽  
Mesoscale Convective ◽  
Westerly Flow

Abstract Mesoscale model forecasts were carried out beginning at 0000 UTC 19 August for simulating Tropical Disturbance 4, which was named Tropical Storm Debby on 22 August 2006. The Weather Research and Forecasting model, with 25-km grid spacing and an inner nested domain of 5-km grid spacing, was used. The development of a small closed vortex at approximately 0600 UTC 20 August 2006 at 850 hPa was found off the coast of Guinea in agreement with satellite images in the 5-km simulation. Intense convection offshore and over the Guinea Highlands during the morning of 20 August 2006 led to the production of a vortex formation by 1400 UTC at 700 hPa. Sensitivity tests show that the Guinea Highlands play an important role in modulating the impinging westerly flow, in which low-level flow deflections (i.e., northward turning) enhance the cyclonic circulation of the vortex formation. Yet, the moist air can be transported by the northward deflection flow from lower latitudes to support the development of mesoscale convective systems (MCSs). Although the model forecast is not perfect, it demonstrates the predictability of the formation and development of the tropical disturbance associated with the Guinea Highlands.

Investigation of the Ferry Disaster Incident of Assam (India) on April 30, 2012

2013 ◽  
Vol 8 (6) ◽  
pp. 1068-1070
Author(s):  
Kalyan Kumar Das ◽  
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Disaster Mitigation ◽  
Severe Thunderstorm ◽  
Loss Of Life ◽  
Convective Systems ◽  
The North ◽  
Severe Thunderstorms ◽  
North Eastern ◽  
Mesoscale Convective

This paper deals with a ferry disaster that occurred in the state of Assam due to a severe thunderstorm. Such storms are locally called Kalbaishakhi or “Nor’westers.” Kalbaishakhi storms are due to pre monsoon (March to May) mesoscale convective systems that develop over the Gangetic West Bengal and the north-eastern part of India. Severe thunderstorms are responsible globally for large amount of wind induced damage. Unlike large or continental cyclones, severe local storms intensify very rapidly and dissipate after causing damage. The worst type of severe local storm is the tornado, which is characterized by a fast rotating column of rising air that originates on or near the ground, where the air swirls and converges at high speed. Another type is the downburst, an antitornadic storm characterized by slow rotating column of descending air, that bursts out violently upon reaching the ground. The focus of this paper is a large scale destroyer of life believed to have occurred due to a downburst from a severe thunderstorm. Such unfortunate natural calamities are eye-openers to agencies working on disaster mitigation and are an important reason for them to implement measures safeguarding against loss of life and destruction of property.

scholarly journals Origins of Vorticity in a Simulated Tornadic Mesovortex Observed during PECAN on 6 July 2015

2019 ◽  
Vol 147 (1) ◽  
pp. 107-134 ◽  
Author(s):  
Matthew D. Flournoy ◽  
Michael C. Coniglio
Keyword(s):  
Convective System ◽  
Vertical Vorticity ◽  
Low Level ◽  
Convective Systems ◽  
The North ◽  
Mesoscale Convective ◽  
Forecasting System ◽  
Convection Initiation ◽  
Inflow Jet ◽  
Gust Front

To better understand and forecast nocturnal thunderstorms and their hazards, an expansive network of fixed and mobile observing systems was deployed in the summer of 2015 for the Plains Elevated Convection at Night (PECAN) field experiment to observe low-level jets, convection initiation, bores, and mesoscale convective systems. On 5–6 July 2015, mobile radars and ground-based surface and upper-air profiling systems sampled a nocturnal, quasi-linear convective system (QLCS) over South Dakota. The QLCS produced several severe wind reports and an EF-0 tornado. The QLCS and its environment leading up to the mesovortex that produced this tornado were well observed by the PECAN observing network. In this study, observations from radiosondes, Doppler radars, and aircraft are assimilated into an ensemble analysis and forecasting system to analyze this event with a focus on the development of the observed tornadic mesovortex. All ensemble members simulated low-level mesovortices with one member in particular generating two mesovortices in a manner very similar to that observed. Forecasts from this member were analyzed to examine the processes increasing vertical vorticity during the development of the tornadic mesovortex. Cyclonic vertical vorticity was traced to three separate airstreams: the first from southerly inflow that was characterized by tilting of predominantly crosswise horizontal vorticity along the gust front, the second from the north that imported streamwise horizontal vorticity directly into the low-level updraft, and the third from a localized downdraft/rear-inflow jet in which the horizontal vorticity became streamwise during descent. The cyclonic vertical vorticity then intensified rapidly through intense stretching as the parcels entered the low-level updraft of the developing mesovortex.

scholarly journals Evaluation of Probabilistic Precipitation Forecasts Determined from Eta and AVN Forecasted Amounts

2007 ◽  
Vol 22 (1) ◽  
pp. 207-215 ◽  
Author(s):  
William A. Gallus ◽  
Michael E. Baldwin ◽  
Kimberly L. Elmore
Keyword(s):  
Mesoscale Model ◽  
Warm Season ◽  
Precipitation Forecast ◽  
Relative Operating Characteristic ◽  
Convective Systems ◽  
The North ◽  
Weather Events ◽  
Skill Scores ◽  
Mesoscale Convective ◽  
Probability Of Precipitation

Abstract This note examines the connection between the probability of precipitation and forecasted amounts from the NCEP Eta (now known as the North American Mesoscale model) and Aviation (AVN; now known as the Global Forecast System) models run over a 2-yr period on a contiguous U.S. domain. Specifically, the quantitative precipitation forecast (QPF)–probability relationship found recently by Gallus and Segal in 10-km grid spacing model runs for 20 warm season mesoscale convective systems is tested over this much larger temporal and spatial dataset. A 1-yr period was used to investigate the QPF–probability relationship, and the predictive capability of this relationship was then tested on an independent 1-yr sample of data. The same relationship of a substantial increase in the likelihood of observed rainfall exceeding a specified threshold in areas where model runs forecasted higher rainfall amounts is found to hold over all seasons. Rainfall is less likely to occur in those areas where the models indicate none than it is elsewhere in the domain; it is more likely to occur in those regions where rainfall is predicted, especially where the predicted rainfall amounts are largest. The probability of rainfall forecasts based on this relationship are found to possess skill as measured by relative operating characteristic curves, reliability diagrams, and Brier skill scores. Skillful forecasts from the technique exist throughout the 48-h periods for which Eta and AVN output were available. The results suggest that this forecasting tool might assist forecasters throughout the year in a wide variety of weather events and not only in areas of difficult-to-forecast convective systems.

scholarly journals Wind and Wind Power Ramp Variability over Northern Mexico

Atmosphere ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1281
Author(s):  
Karla Pereyra-Castro ◽  
Ernesto Caetano ◽  
Oscar Martínez-Alvarado ◽  
Ana L. Quintanilla-Montoya
Keyword(s):  
Wind Power ◽  
Diurnal Variability ◽  
Northern Mexico ◽  
Convective Systems ◽  
Wind Variability ◽  
The North ◽  
Mesoscale Convective ◽  
Strong Winds ◽  
Wind Resource ◽  
The Impact

The seasonal and diurnal variability of the wind resource in Northern Mexico is examined. Fourteen weather stations were grouped according to the terrain morphology and weather systems that affect the region to evaluate the impact on wind ramps and high wind persistent events. Four areas driven by weather systems seasonality are identified. Wind power ramps and persistent generation events are produced by cold fronts in winter, while mesoscale convective systems and local circulations are dominant in summer. Moreover, the 2013 wind forecast of the Rapid Refresh Model (RAP) and the North American Mesoscale Forecast System (NAM) forecast systems were also assessed. In general, both systems have less ability to predict mesoscale events and local circulations over complex topography, underestimating strong winds and overestimating weak winds. Wind forecast variations in the mesoscale range are smoother than observations due to the effects of spatial and temporal averaging, producing fewer wind power ramps and longer lasting generation events. The study carried out shows the importance of evaluating operational models in terms of wind variability, wind power ramps and persistence events to improve the regional wind forecast. The characteristics of weather systems and topography of Mexico requires model refinements for proper management of the wind resource.

scholarly journals Convective Systems of the North Australian Monsoon

2008 ◽  
Vol 21 (19) ◽  
pp. 5091-5112 ◽  
Author(s):  
Mick Pope ◽  
Christian Jakob ◽  
Michael J. Reeder
Keyword(s):  
Active Phase ◽  
Zonal Flow ◽  
Northern Australia ◽  
Australian Monsoon ◽  
Convective Systems ◽  
The North ◽  
Early Afternoon ◽  
Temperature Thresholds ◽  
Mesoscale Convective ◽  
Geostationary Meteorological Satellite

Abstract The climatology of convection over northern Australia and the surrounding oceans, based on six wet seasons (September–April), is derived from the Japanese Meteorological Agency Geostationary Meteorological Satellite-5 (GMS-5) IR1 channel for the years from 1995/96 to 2000/01. This is the first multiyear study of this kind. Clouds are identified at two cloud-top temperature thresholds: 235 and 208 K. The annual cycle of cloudiness over northern Australia shows an initial (October–November) buildup over the Darwin region before widespread cloudiness develops over the entire region during the monsoon months (December–February), followed by a northward contraction during March and April. Tracking mesoscale convective systems (MCSs) reveals that both the size of the cloud systems and their lifetimes follow power-law distributions. For short-lived MCSs (less than 12 h), the initial expansion of the cloudy area is related to the lifetime, with mergers important for long-lived MCSs (greater than 24 h). During periods of deep zonal flow, which coincide with the active phase of the monsoon, the number of convective elements in the Darwin region peaks in the early afternoon, which is characteristic of the diurnal cycle over land. In contrast, when the zonal flow is deep and easterly and the monsoon is in a break phase, the areal extent of the convective elements in the Darwin region is greatest in the late morning, which is more typical of maritime convection.

scholarly journals Observation- and numerical-analysis-based dynamics of the Uttarkashi cloudburst

2015 ◽  
Vol 33 (6) ◽  
pp. 671-686 ◽  
Author(s):  
C. Chaudhuri ◽  
S. Tripathi ◽  
R. Srivastava ◽  
A. Misra
Keyword(s):  
Land Surface ◽  
Wrf Model ◽  
Weather Research And Forecasting ◽  
Moisture Condition ◽  
Near Surface ◽  
Convective Systems ◽  
Mesoscale Convective ◽  
E Region ◽  
Triggering Mechanisms ◽  
Atmospheric Variables

Abstract. A Himalayan cloudburst event, which occurred on 3 August 2012 in the Uttarkashi (30.73° N, 78.45° E) region of Uttarakhand, India, was analyzed. The near-surface atmospheric variables were analyzed to study the formation, evolution, and triggering mechanisms of this cloudburst. In order to improve upon the understanding provided by the observations, numerical simulations were performed using the Weather Research and Forecasting (WRF) model, configured with a single domain at 18 km resolution. The model was tuned using variation of different parameterizations (convective, microphysical, boundary layer, radiation, and land surface), and different model options (number of vertical levels, and spin-up time), which resulted in a combination of parameters and options that best reproduced the observed diurnal characteristics of the near-surface atmospheric variables. Our study demonstrates the ability of WRF in forecasting precipitation, and resolving synoptic-scale and mesoscale interactions. In order to better understand the cloudburst, we configured WRF with multiply nested two-way-interacting domains (18, 6, 2 km) centered on the location of interest, and simulated the event with the best configuration derived earlier. The results indicate that two mesoscale convective systems originating from Madhya Pradesh and Tibet interacted over Uttarkashi and, under orographic uplifting and in the presence of favorable moisture condition, resulted in this cloudburst event.

scholarly journals In Situ Initiation of East Pacific Easterly Waves in a Regional Model

2017 ◽  
Vol 74 (2) ◽  
pp. 333-351 ◽  
Author(s):  
Adam V. Rydbeck ◽  
Eric D. Maloney ◽  
Ghassan J. Alaka
Keyword(s):  
Wrf Model ◽  
Warm Pool ◽  
Early Morning ◽  
Mesoscale Convective Systems ◽  
Weather Research And Forecasting ◽  
Easterly Waves ◽  
Convective Systems ◽  
East Pacific ◽  
Mesoscale Convective

Abstract The in situ generation of easterly waves (EWs) in the east Pacific (EPAC) is investigated using the Weather Research and Forecasting (WRF) Model. The sensitivity of the model to the suppression of EW forcing by locally generated convective disturbances is examined. Specifically, local forcing of EWs is removed by reducing the terrain height in portions of Central and South America to suppress robust sources of diurnal convective variability, most notably in the Panama Bight. High terrain contributes to the initiation of mesoscale convective systems in the early morning that propagate westward into the EPAC warm pool. When such mesoscale convective systems are suppressed in the model, EW variance is significantly reduced. This result suggests that EPAC EWs can be generated locally in association with higher-frequency convective disturbances, and these disturbances are determined to be an important source of EPAC EW variability. However, EPAC EW variability is not completely eliminated in such sensitivity experiments, indicating the importance for other sources of EW forcing, namely, EWs propagating into the EPAC from West Africa. Examination of the EW vorticity budget in the model suggests that nascent waves are zonally elongated and amplified by horizontal advection and vertical stretching of vorticity. Changes in the mean state between the control run and simulation with reduced terrain height also complicate interpretation of the results.

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