What was duration of the longest trip started on the day that has a maximum wind speed of 30 mph?
longest trip refers to MAX(duration); started on the day refers to start_date; maximum wind speed refers to max_wind_speed_mph; max_wind_speed_mph = 30;
SELECT T1.duration FROM trip AS T1 INNER JOIN weather AS T2 ON T2.zip_code = T1.zip_code WHERE T2.max_wind_Speed_mph = 30 ORDER BY T1.duration DESC LIMIT 1