What does the remark 'RAB35' indicate for KMDW?

The remark 'RAB35' indicates that rain began at 1835Z (Zulu time, which corresponds to UTC). The 'RA' stands for rain, and the 'B35' signifies the time at which the rain started, expressed in Zulu time, where '35' refers to the minutes past the hour (in this case, 35 minutes after 18:00 or 6 PM UTC). This notation is used in aviation weather reports to communicate significant changes in weather conditions that could affect flight safety and operations.

In this context, understanding the format of these weather remarks is crucial for pilots and aviation personnel. The correct interpretation of such reports assists in making informed decisions regarding flight planning and safety.

The other choices do not accurately capture the meaning of 'RAB35.' For instance, the first option discusses visibility reduction due to mist, which is unrelated to the 'RAB' remark. The third option refers to a change in barometric pressure, which is not conveyed by the reported rain beginning time. Lastly, while wind direction changes could be part of weather reporting, they are not specifically indicated by the 'RAB35' remark.