Transcript meteo_1_lecture_9

Meteo 1 Lecture 9
• CH 11 HURRICANES (review)
• CH 9 WEATHER FORCASTING
• Weather Forecasting Activity
o Activity 6 in class
o Activity 7 homework
• Video Presentation and Paper
REVIEW SLIDES:
Hurricane Elena over the Gulf of Mexico about 130 km (80 mi) southwest of
Apalachicola, Florida, as photographed from the space shuttle Discovery during
September, 1985. Because this storm is situated north of the equator, surface
winds are blowing counterclockwise about its center (eye). The central pressure
of the storm is 955 mb, with sustained winds of 105 knots (121 mi/hr) near its
eye.
REVIEW SLIDES:
intensifying tropical cyclone
air pressure drops rapidly as you approach the eye of the storm
surface winds normally reach maximum strength in the region of the eyewall
REVIEW SLIDES:
Visible satellite image showing four tropical systems, each in a
different stage of development.
REVIEW SLIDES:
Regions where tropical storms form (orange shading), the names given
to storms, and the typical paths they take (red arrows).
Meteo 1 Lecture 9
CH 9 WEATHER FORCASTING
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Acquisition of Weather Data
Weather Forecasting Methods
Types of Forecasts
Weather Forecasting Using Surface Charts
First, lets review some of the meteorologic factors that contribute to weather:
http://ww2010.atmos.uiuc.edu/%28Gh%29/guides/mtr/fcst/home.rxml
A sounding of air temperature, dew point, and winds at Pittsburgh,
PA, on January 14, 1999.
The geostationary satellite moves through space at the same rate
that the earth rotates, so it remains above a fixed spot on the
equator and monitors one area constantly.
Polar-orbiting satellites scan from north to south, and on
each successive orbit the satellite scans an area farther to
the west.
Generally, the lower the cloud,
the warmer its top. Warm
objects emit more infrared
energy than do cold objects.
Thus, an infrared satellite
picture can distinguish warm,
low (gray) clouds from cold,
high (white) clouds.
http://www.weather.gov/satellite?image=ir#vis
http://www.weather.gov/satellite?image=ir#wv
http://www.weather.gov/satellite?image=ir
http://www.hpc.ncep.noaa.gov/noaa/noaa.gif
Weather Forecasting Methods
First, lets preview some of the forecasting methods:
http://ww2010.atmos.uiuc.edu/%28Gh%29/guides/mtr/fcst/mth/prst.rxml
• Why Forecasts Go Awry
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Assumptions
Models not global
Regions with few observations
Cannot model small-scale features
All factors cannot be modeled
• Ensemble Forecasts:
– Spaghetti model, robust
• Observation: Weathercasters
– Chroma key or color separation
Two 500-mb progs for 7 p.m. EST, July 12, 2006 — 48 hours into the future.
Prog (a) is the WRF/NAM model, with a resolution (grid spacing) of 12 km,
whereas prog (b) is the GFS model with a resolution of 60 km. Solid lines on
each map are height contours, where 570 equals 5700 meters. Notice how the
two progs (models) agree on the atmosphere’s large scale circulation. The
main difference between the progs is in the way the models handle the low off
the west coast of North America.
Model (a) predicts
that the low will dig
deeper along the
coast
model (b) predicts a
more elongated
west-to-east (zonal)
low.
The 500-mb
analysis for 7 p.m.
EST, July 12, 2006.
Ensemble 500-mb
forecast chart for July
21, 2005 (48 hours into
the future).
The chart is
constructed by
running the model 15
different times, each
time beginning with a
slightly different
initial condition. The
blue lines represent
the 5790-meter
contour line; the red
lines, the 5940meter contour line;
and the green line,
the 500-mb 25-year
average, called
climatology.
Probability of a “White Christmas”—one inch or more of snow on the
ground—based on a 30-year average. The probabilities do not include all of the
mountainous areas in the western United States. (NOAA)
The 90-day outlook for (a) precipitation and (b) temperature for
February, March, and April, 2011.
For
precipitation
(a), the darker
the green
color the
greater the
probability of
precipitation
being above
normal,
whereas the
deeper the
brown color
the greater the
probability of
precipitation
being below
normal.
For
temperature
(b), the darker
the
orange/red
colors the
greater the
probability of
temperatures
being above
normal,
whereas the
darker the
blue color, the
greater the
probability of
temperatures
being below
normal.
Weather Forecasting Using Surface
Charts
Movement of Weather Systems, some generalizations:
1. Mid-lat cyclones move in same direction and speed
as previous 6 hrs
2. Lows move in direction parallel the isobars in the
warm air ahead of the cold front
3. Lows move toward region of greatest pressure drop
Surface weather map for 6:00 a.m. Tuesday. Dashed lines indicate positions of weather
features six hours ago. Areas shaded green are receiving rain, while areas shaded
white are receiving snow, and those shaded pink, freezing rain or sleet.
BONUS SLIDE
A 500-mb chart for 6:00 a.m. Tuesday, showing wind flow.
The light orange L represents the position of the surface low. The winds aloft
tend to steer surface pressure systems along and, therefore, indicate that the
surface low should move northeastward at about half the speed of the winds at
this level, or 25 knots. Solid lines are contours in meters above sea level.
BONUS SLIDE
Projected 12- and 24-hour movement of fronts, pressure systems, and
precipitation from 6:00 a.m. Tuesday until 6:00 a.m. Wednesday. (The dashed
lines represent frontal positions 6 hours ago.)
BONUS SLIDE
Surface weather map for 6:00 a.m. Wednesday.
BONUS SLIDE
Forecast on your own!
BONUS SLIDE
Meteo 1 Lecture 9
CH 9 WEATHER FORCASTING
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Acquisition of Weather Data
Weather Forecasting Methods
Types of Forecasts
Weather Forecasting Using Surface Charts
Weather Map Activity 6
• 30 Points
• Launch other Presentation
Weather Forecast Activity 7
• 30 Points
• Homework to forecast the weather and test
one’s forecast
Meteo 1 Fall 2012
Activity 7 Weather Forecasting (2 parts)
30 points!
Part 1 Forecast:
Prepare a weather forecast for two cities (one on the west coast and one on the interior, like
Utah, Colorado, or Kansas). The forecast may be completed at any time before our next class.
The forecast and the Part 2 comparison need to be submitted the day before the intended
forecast day (eg. if one is forecasting the weather on Wednesday, then one needs to submit
the forecast before midnight of the night between Tuesday and Wednesday). The forecast
consists of the following elements:
*During the period from midnight - 11:59 PM, local time
City 1 Coastal ________________________
Maximum temperature*
Justification for your maximum temperature forecast
Minimum temperature*
Justification for your minimum temperature forecast
Wind speed at noon
Justification for your wind speed forecast
Wind direction at noon
Justification for your wind direction forecast
Homework Activity Source:
https://pantherfile.uwm.edu/kahl/www/Forecast/
NWS: monthly and seasonal outlook maps:
http://www.cpc.ncep.noaa.gov/products/predictions/multi_season/13_seasonal_ou
tlooks/color/churchill.php
NWS Hydrometeorological Prediction Center
http://www.hpc.ncep.noaa.gov/
Learning lesson: drawing conclusions:
http://www.srh.noaa.gov/jetstream/synoptic/ll_analyze.htm
jetstream online school for weather:
http://www.srh.noaa.gov/jetstream/synoptic/synoptic_intro.htm
NOAA Environmental Visualization Gallery:
http://www.nnvl.noaa.gov/Atmosphere.php