Checking the 00 to 12 UTC Charts
Now we'll review the 00 to 12 UTC forecasts, paying particular attention to conditions that could impact winds, relative humidity, and the stability of the lower levels of the atmosphere. Click each tab to view the forecasts, then answer the questions below.
Windspeed
Humidity
MSLP
Question 1: Based on the model forecasts, how do you expect the low-level winds to change? Select the correct option.
The correct answer is C.
Low-level winds in the stable layer do not change significantly over the forecast period. They are light but not calm, making D incorrect. Winds in the upper levels do not show a significant increase so A is incorrect. More generally, winds are not expected to increase significantly over time so B is also wrong.
Question 2: What does the relative humidity cross section indicate about the atmosphere around Nairobi? Select all that apply.
The correct answers are B and D.
During the early morning hours (00 to 06 UTC), the air near the airport is relatively moist up to 700 hPa, with values of 70% or above. The air above 700 hPa is much drier, with values falling below 30%. By late morning, the moist layer is lifted and the air in the lowest levels dries.
Question 3: What seasonal weather system is indicated by the mean sea level pressure configuration over the region? Select the correct option.
The correct answer is A.
The main meteorological feature during this season is generally the East African ridge, which is over the continent at this time. The ridge rises from the Mascarene high pressure cell in the south. The East African low-level jet is present but further to the east over the Indian Ocean. The jet brings cold air from the south, which creates a temperature inversion that leads to stable conditions at lower levels and unstable conditions aloft. This is a conducive environment for the formation of low clouds.
Question 4: Based on the NWP data, how will the forecast conditions affect the stratus deck and the potential for the development of fog? Select all that apply.
The correct answers are B, C, and D.
Moist conditions in the lower levels and the dry middle troposphere will enhance radiative cooling. This will promote the development of fog and support the persistence of stratus clouds.