a. The minimum temperature depends on the origin and trajectory of an air mass. Air mass temperature advected over the station will not be modified by local effects if the forecast wind direction for KNPA remains between 280 degrees. and 010 degrees. However, a wind from 020 degrees to 090 degrees advects the air mass over the usually warmer waters of the bay system westward over the NASP complex. This increases the minimum local temperature by 5-10 degrees F. Local area minimum temperatures are influenced by the Gulf the entire year. Local minimum temperature will be modified by any wind from 120 degrees to 260 degrees depending on the open Gulf's temperature.

b. Maximum temperatures are influenced by the Gulf from May through September. During these months,  the Bermuda High is ridging into the central and western Gulf.  Land and sea breezes are the predominant wind regime during this period.

     1) Typically, the temperature increases steadily from the morning minimum. When the local convective temperature is reached, the wind begins to shift from a land breeze to a sea breeze.  The average maximum temperature with a sea breeze will be about 7 degrees F above the Gulf water temperature. 

      2) The absolute maximum temperature will be on average 3 degrees F higher than the average maximum. The absolute maximum will be reached just before the full onset of the sea breeze. After the onset of the sea breeze, the temperature will drop to the average maximum temperature.

      3) When an extreme maximum temperature occurs at KNPA, it is the result of abnormal synoptic situations precluding the onset of a sea breeze.

            a)  A quasi-stationary high pressure area with an identifiable center at 700 mb is located over central Mississippi may produce a north to northwest flow in the lower levels that is stronger than the sea breeze. This will prevent the onset of the sea breeze, and allow extreme maximum temperature to be reached.

            b) A tropical disturbance located in the eastern Gulf or extreme western Atlantic that produces a low-level northerly gradient that is stronger than the sea breeze may allow the development of extreme maximum temperatures.