Kelen Martins Andrade

EXTREME PRECIPITATION EPISODE IN RIO DE JANEIRO: SYNOPTIC ANALYSIS, NUMERICAL SIMULATION AND COMPARISON AMONG PREVIOUS EVENTS

The purpose of this study is to analyze the synoptic pattern and to verify the skill of numerical models (ETA15km, BRAMS20km and GFS) for intense rainfall event in the coastal of São Paulo and Rio de Janeiro states, Baixada Fluminense and the Mountain Region of Rio de Janeiro in march 17-18, 2013. In some places the rainfall in 24 hours exceeded 100 mm, reaching maximum of 424.5 mm in Petropolis. An objective tool was used for obtaining synoptic patterns occurred in the past similar to the extreme event studied. Heavy precipitation was caused by the presence of a cold front associated with intense low levels circulation, contributing for moisture advection from Atlantic Ocean toward the continent. The regional numerical models satisfactorily predicted the heavy rainfall episode. However, the intensity and location of heavy rainfall is still a challenge for numerical modeling.

Características das Frentes Frias Causadoras de Chuvas Intensas no Leste de Santa Catarina

This article analyze the main characteristics of cold fronts yielding heavy rains on the coast of the State of Santa Catarina with the further purpose of improving its knowledge and prediction. A synoptic climatology was performed using NCEP CFSR reanalyzes and CPTEC/INPE precipitation data for the1998-2010 period, considering 5% of the wettest cases. Results showed that cold fronts causing heaviest precipitation have a rather uniform temporal distribution along the year, associated with strong, cold and rather barotropic troughs at middle and upper levels. The slow meteorological evolution allows a progressive low-level trough deepening that increase temperature and moist advection from the Amazon to eastern Santa Catarina thus intensifying thermodynamic instability. The cold front that triggers precipitation has strong low-level tilt and slow movement. Atmospheric conditions linked to frontal passages causing heavier precipitation have minor seasonal variability and can be detected at least 48 hours in advance.

CARACTERÍSTICAS DAS FRENTES FRIAS COM POTENCIAL PARA PROVOCAR CHUVAS INTENSAS NA REGIÃO SERRANA DE RIO DE JANEIRO (CHARACTERISTIS OF COLD FRONTS WITH POTENTIAL TO CAUSE HEAVY RAINFALL OVER THE MONTAINOUS REGION OF RIO DE JANEIRO)

A Regiao Serrana do Estado de Rio de janeiro e uma das mais expostas aos desastres naturais devido a sua orografia, climatologia e ocupacao demografica desordenada. Boa parte da precipitacao anual nessa regiao e explicada pela atuacao de sistemas frontais. Neste trabalho se realiza uma caracterizacao das frentes frias responsaveis pelos maiores volumes pluviometricos diarios. As situacoes foram escolhidas utilizando criterios objetivos aplicados as analises do CFSR para o periodo 1998-2010. Os dados de precipitacao utilizados incluem dados de pluviometros locais e estimativas por sensores remotos. As frentes causadoras dos maiores acumulados diarios ocorrem durante o semestre quente do ano. Nesse periodo elas se diferenciam dos sistemas que causam chuvas inferiores a 5.0 mm/dia ja com dois dias de antecedencia, quando a frente fria se encontra sobre o Uruguai. Inicialmente, a presenca de uma onda relativamente barotropica sobre o Oceano Atlântico prolonga a adveccao de ar quente e umido desde o Noroeste sobre o centro-sul do pais. O posterior acoplamento dessa perturbacao com uma onda mais curta e baroclinica determina o avanco mais rapido da frente fria, assim como sua intensificacao em termos de contraste de temperatura, adveccao de vorticidade e divergencia em altura. Esses fatores, somados a maior umidade e temperatura da massa de ar precedente, explicam a ocorrencia de chuvas mais volumosas.

Aplicação de uma ferramenta objetiva para previsão de tempo severo em ambiente operacional

This study discusses the feasibility of employing an objective forecasting tool in an operational environment, with main purpose of aiding the human forecaster in the task of thunderstorm prediction. The method is based on the combination of widely documented convective parameters, such as K, Total Totals and SWEAT instability indices. Charts were produced to help the identification of areas with high potential to generate storms, defined by specific criteria for severe weather. An alternative for detecting areas favorable to hail occurrence was also presented for identifying those events originated by strong dynamical forcing. The thresholds used were important to characterize the precipitation behavior, allowing them to discriminate different convective modes. The results showed that the objective tool can be an efficient alternative for thunderstorm prediction in South America because it allows the forecaster to overcome some of the limitations found in numerical models, particularly with respect to precipitation forecasting.