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)