midterm Flashcards

Question

What synoptic parameters can we look at to predict rain vs. snow?

Answer 1

The 540 line -The 1000-500mb thickness! 540 gpm line evaluated at 500 mb Thickness is proportional to average virtual temperature between two levels of the atmosphere. - Warmer air = thicker column - Colder air = shallow column So what is the height at 500 mb? - Greater than 5,400 gpm = rain - Less than 5,400 gpm = snow Where on the 500 mb chart does the 540 line fall. - North of the line: snow - South of the line: rain

Answer 2

The Planetary Scale: - Examine changes in the hemispheric pattern over past 3-5 days: - Look at progression of Rossby waves (i.e. troughs and ridges) at 300 and 500 mb. - Are there blocking patterns? - Is the flow mostly zonal or are there waves? Synoptic Pattern: - Warm and cold air advection - Frontal systems - Jet streaks - Rossby waves (i.e. troughs/ridges) - Cyclones/anticyclones Mesoscale Processes: - Convection - Topographic/geographic effects (i.e. upslope, mountain-valley circulation, urban heat island, land/sea breeze circulation, cold air pooling in low area) - Remnant outflow boundaries or mesoscale convective vortices (low pressure generated from convection) from previous convection - Lake effect snow (often poorly resolved in models!)

Answer 3

Radiosondes/Rawinsondes (wind speed and direction)/Soundings (weather balloons)

Answer 4

Surface 850 mb (1500 gpm) 700 mb (3100 gpm) 500 mb (5500 gpm) 250/300 mb (9300 gpm)

Answer 5

- High velocity river of air that flows “completely” around the Earth at mid latitudes. - Very well defined at 200 mb in the summer (300 mb in the winter).

Answer 6

- Strength dependent upon the temperature difference between the two air masses. - The jet stream is strongest during the winter, when the temperature difference is greatest. (More equatorward) - The jet stream is weakest during the summer because the temperature difference is smaller. (More poleward)

Answer 7

- Flow is assumed to be parallel to the height contours (Isohypses) - Steers major weather features at all levels of the atmosphere!

Answer 8

- Subgeostrophi: occurs when the centrifugal force counters the PGF via the geostrophic balance model. Winds are expected to be slower than geostrophic speed (Troughs) - Supergeostrophic: occurs when the centrifugal force enhances the PGF. Winds are expected to be faster than geostropic speed (Ridges)

Answer 9

okay pookie!

Answer 10

- Characterized by areas of strong convergence and divergence

Answer 11

slide 15 in the 250/300/500 mb ppt :smork:

Answer 12

- Typically the primary weather makers in a trough - Capable of amplifying/weakening troughs and ridges

Answer 13

Vorticity (Relative): the clockwise or counter-clockwise spin of the atmosphere in relation to a vertical axis

Answer 14

In Northern Hemisphere: -AV (NVA)= anticyclonic= negative vorticity; sinking air and increasing geopotential heights -CV (PVA)= cyclonic= positive vorticity; rising air and falling geopotential heights Vorticity (Absolute): = Relative vorticity + Coriolis Force (lat.) - Abs vorticity is what’s plotted on the 500mb constant pressure chart - Almost always + because planet vorticity is greater than relative vorticity

Answer 15

- Cyclonic vorticity in areas of DIV, positive vorticity with Lows - Anticyclonic vorticity in areas of CON, negative vorticity with Highs

Answer 16

Longwave Flow Pattern: - Typically >1000 km = Warmer under ridges, cooler under troughs - Standard trough/ridge size we are used to - Pay attention to the axis of orientation (mostly for troughs) If the trough is tilted from NW to SE (negative), it means the low pressure has reached its “maturity” and is usually unstable (clouds/precip/storms). - Also be aware of how tight the Isohypses are together (gradient). This helps you understand how the longwave pattern is going to progress over time. Tighter gradient, faster progress. Typically W→E Shortwave: - A “kink” in the height contours is typically indicative of a shortwave flow pattern. Like a small bump within the longwave flow pattern. - With these shortwave patterns, it is important to determine if it is Barotropic or Baroclinic: Barotropic: A region of uniform temperature distribution; a lack of fronts. Weather features remain fairly static (typically with ridges/zonal flow) Baroclinic: A region with a distinct difference in air masses (a separation of warm/cold air) Surface frontal boundaries usually present (typically with troughs and developed low pressure systems). Will likely amplify the ridge/trough. - Usually great areas of temperature advection (especially with troughs/fronts) Cold air to the left of the shortwave trough axis, warm air to the right

Answer 17

Negative = Sinking Motion Regions of surface CAA, negative vorticity adv. Positive = Upward Motion Regions of surface WAA, low level convergence, positive vorticity adv. Correlates with jet streaks and vorticity advection similar to upper levels

Answer 18

The difference between the air temperature and dew point of an area. The smaller the value, the greater the RH. Can be indicative of instability More moisture (higher RH), more unstable Saturation of mid-levels (detects if vertical motion is resulting in clouds/precip) Very helpful in forecasting clouds, depending on the direction of motion Upward vertical motion + high RH (low DPD) = cumulus clouds Horizontal motion (limited vertical motion) + high RH (low DPD) = stratus clouds

Answer 19

Regions where isotherms cut across isohypses - Baroclinic environments These help dictate how highs and lows strengthen or weaken

Answer 20

A channel of increased winds near the surface located in the warm sector of a mid-latitude cyclone (Between a SE High and a NW low) Typically synoptically driven by MLCs Forms due to the PGF between high and low pressure which is turned to the right by the Coriolis Force Can happen pretty much anywhere a MLC exists. Efficient in transporting warm, moist air northward (may also increase severe wx %)

midterm Flashcards

(44 cards)