# Meteorological Piracicaba/2025 Piracicaba Tornado

This article examines a potential tornado that may have occurred in Piracicaba, located in the interior of São Paulo state, Brazil, during the transition from late afternoon to early evening on January 31, 2025. There are uncertainties regarding the confirmation of the damage and the actual touchdown of the tornado, and this study will unravel them. Using multispectral data analysis, including videos from a storm chaser, radar images from IPMet/UNESP, satellite images, sounding data from CPTEC/INPE, and data from CIIAGRO, the study explores the formation, evolution, and atmospheric characteristics of the event.

### Introduction

On January 31, 2025, a rapidly developing supercell may have produced a tornado in Piracicaba, observed at twilight between 7:04 PM and 7:06 PM (10:04 PM to 10:06 PM UTC). The phenomenon was notable primarily for the short duration of the funnel cloud, captured in a single video recorded several kilometers away by a storm chaser. Additionally, the extent of the damage remains uncertain. The objective of this study is to understand the dynamics of the event, identify the meteorological processes involved, and discuss the potential occurrence of an F0 tornado in the area.

### Methodology

Various datasets and methods were used to analyze the event:
* Storm chaser video: Footage taken by Erik dos Santos in the Jardim Itapuã neighborhood shows the onset of the storm, the formation of the funnel cloud, and the appearance of the wall cloud.
* Radar images: Data from IPMet/UNESP in Bauru helped track the formation and movement of the storm across the rural area of Piracicaba.
* Satellite images and CPTEC/INPE sounding data: These allowed for the observation of the rapid cloud development, from the initial stage of cumulonimbus congestus to the evolution of supercells. The data provided insights into the vertical structure and wind shear during the event.
* CIIAGRO data: Indicated a temperature of around 25°C and relative humidity of approximately 80% at the time of the phenomenon.

### Chronology

* Wall cloud at 7:00 PM
* The funnel cloud in its initial phase
* The funnel cloud in its mature phase
* Timelapse of the phenomenon's passage
The storm originated in the central rural area of Piracicaba at approximately 6:50 PM, moving toward the urban area before diverting south. The cloud developed rapidly, transitioning from a cumulonimbus congestus to a mature cumulonimbus within about 30 minutes.
According to sounding data from CPTEC, there was significant wind shear in the Campinas and Piracicaba regions around 7:00 PM on January 31, 2025. This was due to a strong interaction between cold, humid southeast winds from the Atlantic Ocean and hot, dry northwest winds from the interior of São Paulo, which met in an opposing manner.
At 6:55 PM, the storm began with a rain curtain and a reddish sky, indicative of strong instability. Around 7:00 PM, the formation of a wall cloud, a sign of a mesocyclone, and the appearance of mammatus clouds, typical of supercells, were observed. A funnel cloud formed at 7:04 PM and remained visible for a few seconds before dissipating at 7:06 PM. Due to the low light conditions and limited visibility caused by hills and vegetation, the video quality makes it difficult to confirm whether the funnel made contact with the ground.

### Data Analysis

The IPMet/UNESP radar in Bauru indicated an intense storm in the central rural area of Piracicaba, moving toward the urban area. Reports of heavy rainfall and wind gusts were recorded in the region. Satellite images confirmed the rapid growth of the system and the formation of a low-topped supercell (LT).
Atmospheric soundings showed an unstable profile with strong wind shear, which favored the development of the wall cloud. The temperature of 25°C and 80% humidity, as recorded by CIIAGRO, supported the storm and contributed to the formation of the funnel cloud.
The storm chaser video is the only evidence of the phenomenon, but its low quality and the fact that it was filmed kilometers away create uncertainties regarding whether the funnel made contact with the ground. The location of the funnel in the footage suggests it passed near the neighborhoods of Novo Horizonte and Campestre, but the lack of a clearly visible funnel on the ground makes it difficult to confirm the tornado's occurrence.

### Discussion

The data analyzed supports the hypothesis that an F0 tornado may have occurred in the region. Wind shear and the rapid formation of a supercell are factors that favor tornado development. The observed wall cloud is also a typical feature of tornadic events.
The temperature of 25°C suggests there was enough warm air to sustain clouds with significant vertical development. The relative humidity of around 80% helped lift a mass of warm, humid air, promoting the formation of a strong updraft, which facilitated the rapid development of the supercell.
Upon reviewing the footage, it is likely that the phenomenon did touch the ground, although the condensation funnel was not visible, which is a common occurrence. The lack of damage and the short duration of the phenomenon—about two minutes—conclude that a F0 tornado on the Fujita Scale occurred in Piracicaba, Brazil, on January 31, 2025. The tornado affected an uninhabited area in the Jardim Belvedere housing development, in Campestre neighborhood, with no significant damage.

### Conclusion

Based on the observations, it has been confirmed that a low-intensity, short-duration supercell tornado struck the Jardim Belvedere subdivision in the Campestre neighborhood of Piracicaba, Brazil, between 7:04 PM and 7:06 PM (10:04 PM to 10:06 PM UTC) on January 31, 2025. The tornado was triggered by a low-topped supercell that rapidly developed over the city due to the high availability of warm, humid air and strong wind shear at low atmospheric levels, resulting from the interaction between cold, moist winds from the Atlantic Ocean and warmer, drier winds from the interior of São Paulo. The phenomenon was classified as F0 on the Fujita Scale, with wind gusts of less than 100 km/h, due to the lack of significant damage.