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A Brief History of Weather Forecasting. The Beginning: Weather Sayings. "Red Sky at night, sailor's delight. Red sky in the morning, sailor take warning." "Mare's tails and mackerel scales make tall ships take in their sails." "Clear moon, frost soon." .

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The Beginning: Weather Sayings

  • "Red Sky at night, sailor's delight. Red sky in the morning, sailor take warning."

  • "Mare's tails and mackerel scales make tall ships take in their sails."

  • "Clear moon, frost soon."

  • .

  • "Halo around the sun or moon, rain or snow soon."

  • "Rainbow in the morning gives you fair warning."

  • "When the stars begin to huddle, the earth will soon become a puddle."




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The First Weather Forecaster? early networks were started


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The problem: no way to rapidly communicate weather observations

  • This changed around 1845 with the invention of the telegraph



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Weather Prediction Began observations

  • The main approach to weather prediction during the late 1800s and early 1900s…simple extrapolation using simple schematic “models”


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L observations

L

L


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“Ol Probs” observations

Cleveland Abbe (“Ol’ Probabilities”), who led the establishment of a weather forecasting division within the U.S. Army Signal Corps,

Produced the first known communication of a weather probability to users and the public.

Professor Cleveland Abbe, who issued the first public

“Weather Synopsis and Probabilities” on February 19, 1871


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On May 7, 1869, Abbe proposed to the Cincinnati Chamber of Commerce "to inaugurate such a system, by publishing in the daily papers, a weather bulletin, which shall give the probable state of the weather and river for Cincinnati and vicinity one or two days in advance”.

Cleveland Abbe released the first public weather forecast on September 1, 1869.

Following the signing by President Ulysses S. Grant of an authorization to establish a system of weather observations and warnings of approaching storms, on February 19, 1871, Abbe issued the first “official” public Weather Synopsis and Probabilities based on observations taken at 7:35 a.m.


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An early example of a report: Commerce "to inaugurate such a system, by publishing in the daily papers, a weather bulletin, which shall give the probable state of the weather and river for Cincinnati and vicinity one or two days in advance”.

"Synopsis for past twenty-four hours; the barometric pressure had diminished in the southern and Gulf states this morning; it has remained nearly stationary on the Lakes. A decided diminution has appeared unannounced in Missouri accompanied with a rapid rise in the thermometer which is felt as far east as Cincinnati; the barometer in Missouri is about four-tenths of an inch lower than on Erie and on the Gulf. Fresh north and west winds are prevailing in the north; southerly winds in the south. Probabilities [emphasis added]; it is probable that the low pressure in Missouri will make itself felt decidedly tomorrow with northerly winds and clouds on the Lakes, and brisk southerly winds on the Gulf."


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The Next Major Advance Commerce "to inaugurate such a system, by publishing in the daily papers, a weather bulletin, which shall give the probable state of the weather and river for Cincinnati and vicinity one or two days in advance”.

  • The Norwegian Cyclone Model around 1920


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Next Major Advance: Upper Air Observations Became Available from Radiosonde in the 1920’s, 30s, and 40s


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1940s: Upper Air Charts Using the New Data from Radiosonde in the 1920’s, 30s, and 40s

  • Gave a 3D picture of what was happening

  • Learned how the upper flow steered storms, and thus provided a tool for forecasting cyclone movement.


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Upper from Radiosonde in the 1920’s, 30s, and 40s

Level

Chart


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The Development of Numerical Weather Prediction (NWP) from Radiosonde in the 1920’s, 30s, and 40s

  • Vilhelm Bjerknes in his landmark paper of 1904 suggested that NWP was possible.

    • A set of equations existed that could predict the future atmosphere (primitive equations)

    • But it wasn’t practical then because there was no reasonable way to do the computations and sufficient data for initialization did not exist.


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Numerical Weather Prediction from Radiosonde in the 1920’s, 30s, and 40s

  • The advent of digital computers in the late 1940s and early 1950’s made possible the simulation of atmospheric evolution numerically.

  • The basic idea is if you understand the current state of the atmosphere, you can predict the future using the basic physical equations that describe the atmosphere.


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The Eniac from Radiosonde in the 1920’s, 30s, and 40s


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Numerical Weather Prediction from Radiosonde in the 1920’s, 30s, and 40s

One such equation is Newton’s Second Law:

F = ma

Force = mass x acceleration

Mass is the amount of matter

Acceleration is how velocity changes with time

Force is a push or pull on some object (e.g., gravitational force, pressure forces, friction)

This equation is a time machine!


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Numerical Weather Prediction from Radiosonde in the 1920’s, 30s, and 40s

Using a wide range of weather observations we can create a three-dimensional description of the atmosphere… known as the initialization


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Numerical Weather Prediction from Radiosonde in the 1920’s, 30s, and 40s

  • Observations give the distribution of mass and allows us to calculate the various forces.

  • Then… we can solve for the acceleration using F=ma

  • This gives us the future since the acceleration can be used to calculate the velocities in the future.

  • Similar idea with temperature and humidity.


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Numerical Weather Prediction from Radiosonde in the 1920’s, 30s, and 40s

  • These equations can be solved on a three-dimensional grid.

  • As computer speed increased, the number of grid points could be increased.

  • More (and thus) closer grid points means we can simulate (forecast) smaller and smaller scale features. We call this improved resolution.


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A Steady Improvement from Radiosonde in the 1920’s, 30s, and 40s

  • Faster computers and better understanding of the atmosphere, allowed a better representation of important physical processes in the models

  • More and more data became available for initialization

  • As a result there has been a steady increase in forecast skill from 1960 to now.


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Forecast Skill Improvement from Radiosonde in the 1920’s, 30s, and 40s

National Weather Service

Forecast

Error

Better

Year



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Before Satellites We Had a VERY Poor Knowledge of What Was Happening Over the Oceans!

  • As a result, forecasts were often very poor, particularly in coastal locations.

The 1938 Hurricane was basically unforecast


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Better than Star Trek! Happening Over the Oceans!


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Weather Satellites Give Us Much More than Pretty Pictures Happening Over the Oceans!

  • We start with imagery in several wavelengths:

    • Visible

    • Infrared

    • Water vapor (wavelengths where we see the water vapor distribution)

  • Plus many new capabilities


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Each wavelength Happening Over the Oceans!

gives us information


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Cloud and Happening Over the Oceans!

Water Vapor

Track Winds

Based on Geostationary Weather Satellites


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Camano Happening Over the Oceans!

Island

Weather

Radar


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1995-2003+ Happening Over the Oceans!The computers models become capable of simulating/forecasting local weather.

As the grid spacing decreased to 15 km and below… it became apparent that many of the local weather features could often be simulated and forecast by the models.


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The National Weather Service Happening Over the Oceans!

Forecaster at the Seattle National Weather Service Office



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Problems with the Models fail or are inadequate. Why?

  • Some forecasts fail due to inadequacies in model physics…. How the model handles precipitation, friction, and other processes.

    Example: too much precipitation on mountain slopes

  • Intensive work at the UW to address this problems.


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Some forecasts fail due to poor initialization, i.e., a poor starting description of the atmosphere.

This is particularly a problem for the Pacific Northwest, because we are downstream of a relatively data poor region…the Pacific Ocean.


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Pacific Analysis starting description of the atmosphere.

At 4 PM

18 November

2003

Bad Observation


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Eta 48 hr SLP Forecast valid 00 UTC 3 March 1999 starting description of the atmosphere.

3 March 1999: Forecast a snowstorm … got a windstorm instead


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The problem of initialization should lessen as new observation technologies come on line and mature.New ways of using or assimilating the data are also being developed.


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A More Fundamental Problem observation technologies come on line and mature.

  • In a real sense, the way we have been forecasting is essentially flawed.

  • The atmosphere is a chaotic system, in which small differences in the initialization…well within observational error… can have large impacts on the forecasts, particularly for longer forecasts.

  • Not unlike a pinball game….


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A More Fundamental Problem observation technologies come on line and mature.

  • Thus, there is fundamental uncertainty in weather forecasts that can not be ignored.

  • Similarly, uncertainty in our model physics also produces uncertainty in the forecasts.

  • We should be using probabilities for all our forecasts or at least providing the range of possibilities.

  • There is an approach to handling this issue that is being explored by the forecasting community…ensemble forecasts.


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Ensemble Prediction observation technologies come on line and mature.

  • Instead of making one forecast…make many…each with a slightly different initialization

  • Possible to do now with the vastly greater computation resources that are available.


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Verification observation technologies come on line and mature.

The Thanksgiving Forecast 2001

42h forecast (valid Thu 10AM)

SLP and winds

  • Reveals high uncertainty in storm track and intensity

  • Indicates low probability of Puget Sound wind event

1: cent

5: ngps

11: ngps*

8: eta*

2: eta

3: ukmo

6: cmcg

9: ukmo*

12: cmcg*

4: tcwb

7: avn

13: avn*

10: tcwb*


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Ensemble Prediction observation technologies come on line and mature.

  • Can use ensembles to provide a new generation of products that give the probabilities that some weather feature will occur.

  • Can also predict forecast skill!

    • It appears that when forecasts are similar, forecast skill is higher.

    • When forecasts differ greatly, forecast skill is less.


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Ensemble-Based Probabilistic Products observation technologies come on line and mature.


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The End observation technologies come on line and mature.


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