NOWCASTING SEVERE STORMS IN THE CENTRAL AREA OF THE STATE OF SÃO PAULO WITH THE AID OF TITAN - Severe Storm Nowcasting Study Example

Sep 8, 2026

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Severe storm nowcasting for the central area of São Paulo is investigated using the TITAN system with data from Doppler radars at Bauru and Presidente Prudente. The study validates automatic detection and tracking of potentially severe cells and evaluates hail-related signature algorithms. Cells are identified through a 40 dBZ reflectivity threshold and minimum volume, then hail metrics and forecasts are derived, including POH, FOKR, and SSS. A 17 October 1999 hail event demonstrates the approach.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages2

Reading Time5 min

AccessFree to download

I. Introduction

II. Data and Methodology

Doppler radar configuration

Storm identification and tracking with TITAN

Severe storm parameter indicators

III. Discussion and Results

Storm overview

Hail event of 17 October 1999

NOWCASTING SEVERE STORMS IN THE CENTRAL AREA OF THE STATE OF SÃO PAULO WITH THE AID OF TITAN Ana Maria Gomes and Gerhard Held Instituto de Pesquisas Meteorológicas, Universidade Estadual Paulista, Bauru, S.P., Brazil [ana@ipmet.unesp.br](ana@ipmet.unesp.br); [gerhard@ipmet.unesp.br](gerhard@ipmet.unesp.br) (Dated: September 12, 2007) I. INTRODUCTION Until recently very little was available at IPMet to be deployed as a nowcasting tool, once there was no automatic procedure for detecting and tracking potentially severe cells and to forecast their evolution and displacement. Through a collaborative effort with scientists from the National Center for Atmospheric Research (NCAR), the software system TITAN (Thunderstorm Identification, Tracking, Analysis and Nowcasting; Dixon and Wiener, 1993) was made available to analyze radar data information from both radars operated by IPMet. The implementation in IPMet´s computer system was done with the assistance of NCAR staff that helped with all necessary computer routines to be adapted for direct access to the data format generated by both Doppler radars (Kokitsu, 2005) . The results that will be presented here are part of the project validation of the severe events in the central area of the State of São Paulo in compliance with some objectives of the SIHESP (Sistema Hidrometeorológico do Estado de São Paulo) project. The main objective of the study is to verify the potential of the new tools available with the TITAN system and then to transfer the results to the operational sector of IPMet. Results related to a severe event that occurred on 17 October 1999, causing extensive damage by hail, will be presented as an example. II. DATA AND METHODOLOGY The Doppler radars are located at Bauru (Lat: 22.36°S, Lon: 49.02°W, 624 m amsl) and 240 km further west at Presidente Prudente (Figure 1) . The main characteristics of the radar are: 2° beam width and ranges of 450 km for surveillance and 240 km in volume scan mode (11 elevations: 0.3° to 34.9°), 1 km radial and 1° azimuthal resolution, and temporal resolution of 15 min or less, recording reflectivity, radial velocity and spectral width. TITAN was used in the ARCHIVE mode and the tracking properties form the base for the analysis here. A TITAN cell was defined by the 40 dBZ threshold for the reflectivity with a minimum volume of 50 km3, observed at least in two volume scans (15 minutes) . For all storms complying with or exceeding the adopted criteria for storm properties, the hail metrics, as well as the forecasting of its evolution, were determined. Severe Storm Parameter Indicator Besides tracking and nowcasting the movement of storm cells, TITAN has incorporated algorithms that allow identification of potentially severe storm “signatures”, such as hail metrics, to produce probability of hail (POH), based on Waldvogel et al. (1979) . This implies that hail occurs always when the 45 dBZ reflectivity is present at 1.4 km or more above the freezing level. Another parameter, FOKR (Foote-Kraus) index, also related to hail-producing storms, was developed by Foote et al. (2005) and first applied to hail-producing storms in Argentina. Also used for the analysis here is the SSS (Storm Structure Severity) index, developed by Visser (2001) for hailstorms on the South African Plateau. FIG. 1: Doppler radar network of IPMet (BRU = Bauru; PPR = Presidente Prudente), showing range rings for 240 and 450 km. III. DISCUSSION AND RESULTS Storm Overview The severe event on 17 October 1999 developed and evolved in an environment under the influence of a baroclinic system reaching the State of São Paulo. A squall line with multicellular storm characteristics, showing several intense cells forming ahead of the frontal disturbance, with an extended trailing stratiform area, can be seen in Figure 2. FIG 2: Composite reflectivity field for the Bauru and Presidente Prudente radars, 240 km range, on 17/10/1999, 11:22 LT. The ellipses

FAQs

What is the main objective of the study using TITAN?

To verify the potential of new tools in the TITAN system for severe storm detection/nowcasting and to transfer results to IPMet’s operational sector.

How does TITAN define a TITAN cell for analysis?

A cell is defined using a 40 dBZ reflectivity threshold with a minimum volume of 50 km3, observed in at least two volume scans (15 minutes).

Which hail-related indicators are used to evaluate storm severity?

The study uses probability of hail (POH) based on hail signatures and includes the FOKR index, as well as the SSS storm structure severity index.

Sep 8, 2026

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