Why NWS Forecasts go Awry and Steps to Improve Them grid spacing: models cannot resolve features within a grid cell (e.g., 40 km for global models) incomplete data coverage (e.g., over remote regions) model deficiencies due to subgrid processes (e.g., clouds, land surface) Chaos: weather forecasts are highly sensitive to our ability to observe the weather. Since it is impossible to observe the weather at all places at all times, weather forecasts will never be perfect. This is the reason that we cannot predict the weather 1 month or 1 year from the forecasting day. Q: For global model with a grid spacing of 40 km, can you see the Mt. Lemmon or Tucson in the model? a) yes, b) no (Chap. 9; #12)

Q: What does it mean by `chance of (steady) rain is 60% for one area’? a) It will rain over 60% of the area b) 60% chance that any random location in the area will receive measurable rainfall (Chap. 9; #15) Q: Your friend claims that the forecast of 50% chance of rainfall is meaningless as it is the same chance for head in coin tossing. How do you respond? a) agree, b) disagree, c) don’t know Pay attention to the last note

Thunderstorms (Chap. 10; #2) Thunderstorm: storm with lightning and thunder; they are convective storms that form with rising air in a conditionally unstable environment The trigger needed to start air moving upward may be surface heating; topographic lift; convergence zone (e.g., sea breeze leading edge); frontal lift; divergence aloft Q: Conditionally unstable environment means that the environmental lapse rate is a) > 10 K/km, b) < 6 K/km, c) between 6 – 10 K/km (Chap. 10; #2)

(Chap. 10; #28) Tornado Winds multi-vortex tornadoes suction vortices Q: what is the wind speed at A or C? a) 100 knots, b) 112 knots, c) 150 knots

Devastating Winds and the Storm Surge Q: The strongest hurricane wind is located at the place where the hurricane rotational wind and the hurricane movement wind are: a) in the same direction, b) in opposite direction, c) perpendicular to each other Q: Does the Ekman transport increase or decrease the coastal sea level in the figure? a) increase, b) decrease, c) no effect Q: What would cause high ocean at the center? a) surface low pressure, b) high pressure (Chap. 11, #19)

(Chap. 12, #2) Global Temperatures controls on temperature climatology: - intensity of sunshine and its variation with latitude - distribution of land and water and ocean currents - prevailing winds - location of high and low pressure areas - mountain barriers and altitude Q: The Antarctic in the next slide is not so cold, because a) winter and summer average out b) Antarctic is actually not too cold compared to Arctic c) only the equivalent sea-level temperature is shown d) Arctic is simply colder

(Chap. 13, #6) Climate Change and Feedback Mechanisms Feedbacks cause climate changes to be either amplified (positive feedback) or reduced (negative feedback). Q: The water vapor-greenhouse feedback is? a) positive feedback; b) negative feedback c) unknown Q: Why is the snow-albedo feedback positive? A: increasing T decreases snow cover; this decreases surface albedo and hence increases surface solar absorption; leading to further increasing T Q: why is cloud feedback overall negative? A: low clouds are negative by reflecting solar radiation; high clouds are positive just like greenhouse gases; overall low clouds are more dominant, leading to overall negative feedback