What does the remark "RMK FZDZB42 WSHFT 30 FROPA" in a METAR observation indicate?

The remark "RMK FZDZB42 WSHFT 30 FROPA" in a METAR observation is indicating a significant meteorological condition, specifically related to weather changes due to a frontal passage. The notation "WSHFT 30" denotes a wind shift at 30 knots that occurs as a result of the front moving through the area or nearby.

The term "FROPA" emphasizes that this change is associated with the frontal passage, indicating that meteorological observers are reporting the immediate effects of this front on wind patterns. Understanding that wind shifts are integral to frontal activity helps clarify why this answer is correct, as it signifies an essential component of how weather systems interact and affect local weather conditions.

In this context, recognizing what the METAR language means is crucial for weather forecasting and situational awareness in aviation and military operations, where knowing the implications of wind shifts can affect flight safety and tactical planning.