The weather today is caused by a low pressure area. According to the weather forecast, this low pressure area is responsible for the thunderstorms at sea. The exact location of the low pressure area is not specified in the provided evidence, but it is mentioned that it is causing thunderstorms at sea. The weather forecast does not provide information on the expected duration or intensity of the thunderstorms. It only mentions the presence of a low pressure area as the cause of the current weather conditions. The source does not provide any further details on the weather conditions, such as temperature, wind speed, or precipitation levels. The low pressure area is the primary factor affecting the weather today, as stated in the weather forecast.