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ATS/ESS 452: Synoptic MeteorologyFriday 22 Aug 2014
• Finish Overview Presentation• Current Weather Discussion• Begin Review Material
GOES-12 IR satellite
image, 0615 UTC 19
August 2009
GOES-12 IR satellite image of Hurricane Bill at 0615 UTC 19 August 2009
GOES-12 IR satellite
image, 0615 UTC 19
August 2009
06 UTC GFS sea-level pressure (SLP) analysis for Hurricane Bill
Hurricane Bill was forecasted (correctly) to curve harmlessly out to sea.
But WHY did this happen?
GFS 60-h SLP + 500 mb forecast, valid 18Z Aug 21, 2009
What do you see that may be important to Bill’s forecast?
500 mb trough
GFS 84-h SLP + 500 mb forecast, valid 18Z Aug 22, 2009
Notice the interaction between the trough and Hurricane Bill.The upper-level winds associated with the trough will “push” Bill out to sea.
How can we trust the previous GFS forecast for the trough interaction with Bill?
• Model initiation errors?• Did the model initiate Bill at
980mb when it’s really 950mb? Why is this important?
• Forecast consistency
• Many other models… what do they say?
• Ensemble forecasting
• Known model bias
A little more disagreement between model ensemble members.
Today’s Numerical Weather Models Are Pretty Good… Are Humans Still Needed?
• Yes!! But roles are changing
• Need to improve risk communication (e.g. April 27 outbreak), predictability and uncertainty in forecasting
• Skill in augmenting the numerical forecast; local complexities which models often have difficulty in understanding
• Demand is increasing for understanding and applying new technology
• Still LOTS of research questions remain
Start To Get Familiar With…
MOS
NCEP Model Guidance
Another Good Model Site – TwisterData
Another Good Model Site – Earl’s Current Weather Page
Read NWS Area Forecast Discussions – HUN Example
Read SPC Products
HPC Sfc Products and Discussions
Current Weather Discussion
Begin Review Material
Reading Assignment:pp. 1 – 11 from Lackmann
Scales of MotionScale Approximate
Length ScaleApproximate Time
ScaleTypes of Phenomena
Planetary > ~ 6000 km > 1 week
Synoptic Scale
1000 – 6000 km 1 day – 1 week
Mesoscale 1 – 1000 km 1 hour – 1 day
Microscale < 1 km < 1 hour
This information is important for simplifying the equations that describe our atmosphere through a process known as scale analysis
**Determine which physical processes are most important and which can you neglect.
Jet Stream, Trade Winds, Longwave pattern
Shortwaves, Fronts, Jet Streaks
Thunderstorms, Sea Breezes
Turbulence, Boundary Layer Phenomena
Variables, Coordinates, & Units• Cartesian coordinate system (x, y, z) is the most typical coordinate system used in
meteorology- x: zonal (East-West) direction; positive towards the east- y: meridional (North-South) direction; positive to the north- z: vertical (up-dpwn) direction; positive upward
• What other coordinate system do you think we will use?- Pressure coordinates
Quantity Unit SI units and notation
Length Meter M
Time Second S
Mass Kilogram Kg
Temperature Kelvin K
Velocity Meter/Second m s-1
Force Newton N (kg m s-2)
Pressure (force/area) Pascal Pa (N m-2 or kg m-1 s-2)
Energy or work Joule J (N m or kg m2 s-2)
Variables, Coordinates, & UnitsWind velocity are based on the time rate of change in the distance along its respective coordinate axes following the airflow
zonal wind:
meridional wind:
vertical wind:**start to refer to directions using these names
The Coriolis parameter (f) is related to the spin of the Earth and is given by:
where φ is the latitude and Ω is the rate of Earth’s rotation (7.292 x 10-5 rad s-1)