What does the SLP993 6//// in the METAR indicate?

The designation SLP993 in a METAR report refers to the sea-level pressure. The "SLP" stands for sea-level pressure, and the numbers following it indicate the pressure in hectopascals (hPa). In this case, SLP993 corresponds to a pressure reading of 999.3 hPa, which is calculated by adding 1000 hPa to the three digits presented (993).

The double slashes after the number (6////) indicate indeterminate precipitation, meaning that specific information regarding the amount of precipitation is not available or hasn't been recorded. The presence of these slashes indicates that while there is information about the sea-level pressure, details about precipitation over the indicated time frame (six hours) are not valid or were not measured.

In summary, the correct interpretation of SLP993 is that it reflects a sea-level pressure of 999.3 hectopascals, while the accompanying notation suggests that there is no precise data on precipitation.