Weather Forecast Assignment

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Chapter 13

Weather

Forecasting

http://www.weather.com/news/weather/video/step-into-the-future-of-weather-forecasting

http://www.accuweather.com/en/weather-video/channels/bloopers

Weather of the dayyyyyy!

Thanks Alaina!

Derecho

(Putnam county, OH) 6/29/2012

On June 29, 2012, a derecho (deh REYcho) moved east-southeast at 60 miles per hour (mph) from Indiana in the early afternoon to the Mid-Atlantic region around midnight. The states most significantly impacted were Indiana, Ohio, Kentucky, Pennsylvania, West Virginia, Maryland, Virginia, Delaware, New Jersey, and North Carolina, as well as Washington, D.C. Nearly every county impacted by this convective system suffered damages and power outages.

Winds were commonly above 60 mph with numerous reports of winds exceeding 80 mph. Some areas reported isolated pockets of winds greater than 100 mph. The storm resulted in 13 deaths, mainly a result of falling trees. One major impact from the derecho was widespread power outages. More than 4 million customers were without power, some for more than a week after the storms moved through. To make matters worse, the area affected was in the midst of a prolonged heat wave. There were 34 heat related fatalities in areas without power because of the derecho.

http://www.nws.noaa.gov/os/assessments/pdfs/derecho12.pdf

https://www.youtube.com/watch?v=gT8vYDwidao

https://www.youtube.com/watch?v=O15KFbS5bD8

500 mb heights showed no obvious disturbances to indicate derecho development, high press ridge in NW, 45mph at height

Check out the dew points, the temp ahead of the front, ELR

High CAPE. CAPE is directly related to the maximum potential vertical speed within an updraft Circular shape indicates what type of storm?

The storms organized into a large bow echo in eastern
Indiana and raced east-southeast at around 60 mph

Doppler Reflectivity and Base Velocity

Convective Update

Progression

Forecasters undershot warning areas

So, it was a missed forecast with severe consequences. What to do differently?

Establishing a 24-hour warning point and emergency operations center
Having more than one method of receiving severe weather forecasts and alerting the public
Creating a system that monitors local weather conditions
Promoting the significance of public readiness through community seminars
Developing a formal hazardous weather plan that includes training severe weather spotters and holding exercises

The public perception was that even with the warnings, stronger words were needed to make them take heed

Weather Forecasting—Both Art and Science

As you can see with the derecho, forecasting is difficult and encompasses many disciplines, technologies, and tools. Think about all of the measures and tools we have examined so far in class. Temperature, humidity, winds in upper and lower atmosphere, storm behavior, precipitation, sub-solar point, rotation, revolution. Meteorologists take ALL of these into account. Mathematics, physics, chemistry, social sciences. Public perception is half the battle!

Why Is Weather Forecasting Imperfect?

Public perception is that forecasts should be nearly perfect, and people get ANGRY when they are wrong!
Weather forecasting is

extraordinarily difficult, as many

variables are involved that are

constantly changing (temperature,

water content, energy, stability, etc.).

So lets think, if I ask you to tell me

the temp for tomorrow, a forecasters,

what do you need to consider?

Forecasting

Start from beginning of the book: temp structure based of the absorption and scattering of radiation, which depends on the horizontal and vertical distribution of atmospheric gases, clouds, vapor, etc. With water changing between three states constantly, atmospheric composition is hardly constant. As water is changing state, there is constant energy exchange. Latent heat! These phase changes are influenced by vertical up and down drafts, gotta keep an eye on those too. The season, the breezes, wind direction… Ayayeyaye!
Weather forecasting involves a set of interlocking problems, each difficult to solve in isolation, let alone in combination. It should be surprising that they DO get it right, rather than don’t!

Weather Forecasting—Both Art and Science

National Weather Service (NWS) and the Meteorological Service of Canada (MSC) employ forecasters 24/7.
The NWS was established by the US Govt. in the 1870’s, now falls under the direction of NOAA
http://preview.weather.gov/edd/
https://www.youtube.com/watch?v=2XsFnh-7E2w
Every meteorologist has a set of procedures for analyzing the weather, given the situation. There is no defined routine.
Technology has changed things drastically
The Advanced Weather Interactive Processing System (AWIPS) allows forecasters to display all the pertinent weather information available (current weather conditions, output of computer forecast models displayed in map form, satellite and radar images, forecast advisories and discussions from other weather facilities, etc.).

Typical Day

Starts with verbal briefing from a meteorologist finishing shift
Examine a large amount of data, focus per geographic region (tornado look at radar, snow storm satellite)
Multiple screened monitors can display an enormous amount of information to help with decision making
Major weather systems are just the tip of the iceberg
The first step would often be to check cloud cover: Cloud cover can obviously indicate precip, but also is needed to determine temp
You have determine whether the clouds will stick around, thin vs thick, clear skies mean clouds could move in
If its 5 degrees warmer than yesterday AM, then PM will likely be 5 degrees warmer

Weather Forecasting—Both Art and Science

Forecast maps created by the computer models often depict the predicted distribution of weather variables directly as an application of physical laws.
Modeling, predicting behavior
For example, enter in temp, press, upper level flows, shear, etc, etc

Statistical

Other models rely on statistical methods to assist the forecaster.
Statistically, physical models could tell temp zones in NA, statistics can “fill in the blanks”

Other forecasts

Short term forecasts- aviation warnings, hydrological info, etc
Maritime forecast http:// forecast.weather.gov/product.php?site=CLE&issuedby=CLE&product=AFD&format=CI&version=1&glossary=1&highlight=off
The most familiar type of weather statement is the zone forecast, issues at designated times each day and extending out to a week into the future
http://www.erh.noaa.gov/displayprod.php?product=CLEZFPCLE

Forecasting Methods

There are 4 forecasting methods: They can be used separately or together

Climatological forecasts: based on long-term averages, but not current weather conditions, Chicago vs Orlando

Persistence forecasts: based on current conditions, no climatological reference, you do everyday

Analog approach: based on current conditions and similar well-studied patterns from the past. Past precedence, rule of thumb, winter snow about the 5000m contour, high clouds bring precip in 36 hours

Numerical weather forecasting: based on computer programs that mimic the behavior of the atmosphere.

Types of Forecasts

There are 3 types of forecasts:

Quantitative forecasts: “An inch of rain is expected.” “The high is going to be 56 ºF today.”

Qualitative forecasts: categorical, classify, “rain/no rain” or “above/below normal”, cloudy, partly cloudy, etc

Probability (PoP) forecasts: “The rain chance today is 70%.” “There is a 60% chance of snow.”

Types of Forecasts
Prob of Precip Map

Thanks Brianna!

Assessing Forecasts

Measures are needed when comparing one forecast to another, decide which method is best, and when
Assessment measures are needed by those responsible for developing and administering forecasting programs to ensure best practices, justify expenditures, determining ROI
The forecast quality (how close to true) and the forecast value (loss/payoff tables, risk/rewards) can be assessed.
When assessing the forecast quality, forecast accuracy and forecast bias (systematic over or under prediction) can be examined.
Forecast skill can also be a factor, use a baseline of climatology, predicting no rain in Jerusalem in July or a hurricane in September

Assessing Forecasts

Measures are needed when comparing one forecast to another, decide which method is best, and when. You do this when planning vacation!
Assessment measures are needed by those responsible for developing and administering forecasting programs to ensure best practices, justify expenditures, determining ROI
The forecast quality (how close to true) and the forecast value (loss/payoff tables, risk/rewards) can be assessed.
When assessing the forecast quality, forecast accuracy and forecast bias (systematic over or under prediction) can be examined.
Forecast skill can also be a factor, use a baseline of climatology, predicting no rain in Jerusalem of a hurricane in September

Data Acquisition and Dissemination: How does the NWS get all that data?

Data collection is an international effort, blended borders
The World Meteorological Organization (WMO), sanctioned by UN, responsible for data collection across the globe.
Collected from 179 nations, 10,000 land stations, 7000 ship stations, 300 buoys, as well as weather satellites, and 1000 weather balloons, twice a day.
Data is sent to world meteorological centers in Washington D.C., Moscow, and Melbourne. These centers disseminate to the rest of the world.
In the U.S., the National Centers for Environmental Prediction (NCEP) are responsible for processing, and issuing regional and national forecasts.

Data Acquisition and Dissemination

The FAA and NWS have installed a network of more than 800 automated sensors, called Automated Surface Observing System, or ASOS, for measuring and recording temperature, humidity, pressure, cloud conditions, wind direction and speed, visibility, presence of fog or rain, and accumulated precipitation readings at ground level.

Radiosondes, thousands a day, are launched to track pressure, temp, and upper level winds. The balloons ascend for a few hours and burst at the stratosphere.