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How To Optimize
Your Observing Sessions
Using Selected Weather
Web Tools
Night Two
Reg Dunkley
Tonight’s Goals
• Review
• Find Me A Break
– Satellite Web Sites
– Cold Front Example
– Cloud Cover Forecasts
• It is a Go
– The Case of the Lucky Astronomer
• Can You See Water Vapour?
• Latent Heat of Vapourization
• The Gasoline of Hurricanes and
Thunderstorms
• Warm Air Can Hold More
Moisture Than Cold Air
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•
•
•
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Why Don’t Clouds Fall Down?
Convective Updrafts
Miles per Hour
Form Cumuliform Clouds
Buoyant Atmosphere
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•
•
•
Slowly Rising Air
Feet per Hour
Form Stratiform Clouds
Stable Atmosphere
Is Air Distributed Equally?
• Pressure is the weight per unit
area of the air column above you
• More Air = Higher Pressure
• Pressure Difference Creates Wind
• Wind Can Cause Air to Rise and
Sink
• Rising Air Leads to Condensation
and Release of Latent Heat
• Generates Cloud and
Precipitation
• Sinking Air = Clear Skies &
Observing Sessions
Circulation In
Mountainous Terrain
• Flow Tends to be Channeled in
Valleys or along Coast Lines
• Flow Can Be Perpendicular to the
Expected Geostrophic Circulation
Pattern
• Flow will Move from High
Pressure to Low Pressure (eg
Arctic Outflow Winds)
• Flow Complicated By:
– Sea Breeze and Upslope Flows
Driven By Daytime Heating
– Night Time Cold Air Drainage Winds
An Order Within the
Chaos
• The Atmosphere Is Self
Organizing!
• Reoccurring Cloud Patterns with
Hammerhead Swirls and Abrupt
Lines of Change
• Changes Often Include:
– Sudden Clearing and End of
Precipitation
– Wind Shifts
– Changes In Temperature
• Norwegian Frontal Model
– Cold and Warm Air Resist Mixing
– Warm Air Overides Colder Denser
Air
– Cold Air Undercuts Warm Air (Plow
Like)
The Frontal Model
The Frontal Model
Meteorologists Are:
Well Funded Astronomers
Who Focus On
The Most Dynamic Atmosphere
In The Solar System
Satellite Imagery Web
Sites
• University of Washington Atmospheric
•
•
•
•
Sciences
http://www.atmos.washington.edu/~o
vens/loops/
Many Sources With Many Time
Formats
GMT = UTC= Z = PST + 8 Hours = PDT +
7 Hours
Favourites:
– Big Picture GOES Infrared Imagery
– http://www.atmos.washington.edu/~ovens/wxloop.
cgi?ir_common+12
– High Resolution GOES Visual
Imagery
– http://www.atmos.washington.edu/~ovens/w
xloop.cgi?vis1km+12
False Colour Satellite
Imagery
• Place Infrared Channel in the Blue
Gun
• Place Visual Channel in the
Yellow Gun
• Blue Cloud = High Thin Cirrus
Cloud
• Yellow Cloud = Warm Relatively
Low Cloud
• White Cloud = Thick Opaque
Cloud
• Source: Environment Canada
Web Site
• http://weather.gc.ca/satellite/index_e.html#
goes_west
Example of Frontal
Systems
Corresponding Surface Pressure
Analyses
• Lines of constant pressure,
Isobars are drawn at 4 millibar
intervals
• Surface Pressure Analyses can be
obtained at
http://weather.gc.ca/analysis/index
_e.html
• The closer the isobar spacing …
the stronger the wind
It Is A Go!
The Case of the
Lucky Astronomer
Goes Infrared Imagery
Saturday October 18th 2014
GOES Visual Satellite
Imagery
• For Saturday October 18th 2014
Astronomy Cloud
Forecasts
• One Output of Numerical
Weather Models
• “Future Vision” Synthetic Satellite
Images
• Cloud Amount Forecasts for Each
Hour
• Called: Astronomy Sky Condition
Forecast
•
http://weather.gc.ca/astro/clds_v
is_e.html
• From Canadian Meteorological
Centre
Cloud Amount Image vs Clear
Sky Chart
• Forecast Cloud Amount Images:
– Provide Insight into What is
Generating the Cloud
• You Can Compare Forecast
Amount With Actual Satellite
Image To:
– Confirm if Position is Correct
– Confirm if Cloud Amounts are
Correct
• Provides a Level of Confidence in
Forecast
• Allows You to Make Adjustments
• Can Help Optimize Your
Observing Session!
Satellite Web Tools For
Astronomers
– Big Picture GOES Infrared Imagery
• http://www.atmos.washington.edu/~ovens/wxloop
.cgi?ir_common+12
– High Resolution GOES Visual
Imagery
• http://www.atmos.washington.edu/~ovens/wxloop
.cgi?vis1km+12
– False Colour Satellite Imagery
• Select IR + Visible Imagery
• http://weather.gc.ca/satellite/index_e.ht
ml#goes_west
– Astronomy Sky Condition Forecast
•
http://weather.gc.ca/astro/clds_vis_e.
html