Andy_Johnson's Blog

Dense fog blanketed most of the viewing area this morning. We don't get alot of fog days here in the Tampa Bay area. On average we see 19 days a year where the visibility is less than or equal to one quarter of a mile. Of those days, the most (5) are in January, 3.3 in December and 2.8 in February. The average in June is .3 which is due to fog formation the morning after a heavy thunderstorm.

In the winter, we usually see fog after we have a had a cold snap. The reason is that there is a lag between water temperature and air temperature. As cold air moves from the continent across the gulf, the temperature over land drops faster. In this past week, the temperature in Tampa reached 29 on Thursday. As a result the water temperature began cooling and reached 54 in the Gulf Saturday. Now that overnight air temperatures and the dewpoint temperature are above 54 fog forms.

 Remember that to achieve 100% humidity the temperature and dewpoint must be the same. If the dewpoint is higher than the water temperature, the water vapor in the air is easily condensed into fog.