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COMMON FORECASTING MISTAKES

METEOROLOGIST JEFF HABY

Weather forecasting offers new challenges each day. It is important to keep a few things in mind. First, time needs to be set aside each day in order to develop a forecast correctly. Every map adds a new piece to the puzzle. More data studied within a set amount of time will increase forecasting efficiency. With practice, you will be able to look over more data in a shorter length of time.

There are new models and sources of data coming out all the time. After you have developed a forecast "routine" don't forget to look at data that has not been studied for a while. For example, a forecaster may get used to making a forecast without the aid of satellite data. Newer sources of information integrated into the forecast should result in better forecasts over the long term while keeping forecasting interesting and not overly routine.

A common mistake in forecasting is using old data. When studying any analysis or forecasting chart it is important to look at the date and time stamp on the image. Obviously, forecasting with new data will optimize accuracy. Know the Z-time for your local time.

Some forecasts are too general or too specific. Below is an example of these two extremes:

TOO GENERAL: Today the sun will rise. Expect some clouds with mostly cloudy to mostly sunny conditions although there might be a shower or thunderstorm sometime today. The high will be in the 70's and possibly into the 80's if there is lots of sunshine. The low tonight will range from 45 to 60 degrees. Winds will be from the South at 5 to 20 miles per hour.

TOO SPECIFIC: The fog will lift this morning at 9:30am. Expect decreasing clouds with a 100% chance for afternoon thunderstorms. The rain will begin at 2 p.m. and end around 4 p.m. Rainfall accumulation will be about 1/2 inch. The high today will be 87 with a low tonight on 57 . Temperatures will start at 60 at 10 am and gradually warm to the expected high. Temperatures will warm most rapidly at 9:30 am when the fog breaks.

The advantage of the "general" forecast is the fact it has a good chance of being correct. Almost any type of weather could occur and the forecast will still verify. The downfall of course is that the forecast offers very little useful information. The public has a difficult time preparing their day for this type of forecast. The public has no idea what the character of the rainfall will be or when it will start and end. The forecast also has no temperature trend.

The advantage of the "specific" forecast is the forecaster will look like a genius if it verifies. Usually a busted forecast results however. Exact temperatures, exact rain times, exact cloud clearing times, and 100% precipitation chance all have a good chance of being incorrect. Generally, a 100% chance for rain is only given if it is currently raining. Although exact temperatures can be used, a small range such as the upper 50's or between 73 and 76 have a much better chance of verifying.

Mesoscale effects will often produce a temperature range over a viewing area anyway. Predicting exact rainfall amounts is very difficult, especially with convective rain. It is best to use a range of expected rainfall. The larger the forecast region is, the larger this range may have to be. Although pinpointing an exact time for rain is difficult, giving an approximate time for the best chance for rain, such as the afternoon, is better than simply stating there is a chance of rain today. In summary, a forecast should balance in between the "too general" and "too specific" versions to optimize forecast accuracy while at the same time giving the public useful information.

There are phrases in meteorology called "sticking your head out" and "going out on a limb". This refers to giving a forecast that is far different than what is expected by the models and other forecasters or pinpointing where an exact weather event will take place. Examples are: (1) Predicting the county a tornado will occur that day, and (2) Predicting a 12" snowfall when most indications are that heavy snow is unlikely. Forecasting a tornado in a particular county is an example of making a "too specific" forecast. The 12" snowfall is an example of "going out on a limb". Reduce having busted forecasts by being realistic and well informed.

One of the most difficult forecasts to make is the wintry precipitation forecast as well as the fog forecast. Winter weather situations require more time spend examining the weather data. The public is very sensitive to winter forecasts primarily due to the travel headaches they cause. Making a correct wintry precipitation forecast is truly worth celebrating.

The other common busted forecast is the fog forecast. It is a common mistake to "forget" to forecast for fog. Fog forecasts are extremely important to the transportation industry and to all morning commuters. On first inspection, fog forecasting does not seem difficult. Clear skies, light wind, saturated soils, and low dewpoint depressions are the primary ingredients for radiation fog. However, on some occasions these conditions will prevail and no fog develops while in others dense fog develops.

When using radar it is important to examine all the storms on the radarscope. It is a forecasting mistake to follow one storm too closely while ignoring other developing storms. When the radarscope has several storms, it can be very difficult to determine which one will be the "storm of the day". It is best to track all the storms while focusing on the ones that are the most severe at the current time.

Another forecasting mistake to mention is bad communication. The general public knows far less about how the atmosphere works than a meteorologist and most broadcast meteorologists. It is important to relate the weather to the target audience in a way that is understandable. Giving too complex of a description can lead viewers and clients to confusion. Also, make sure the weather information is timely and relevant for that moment.

Lastly, it can be a mistake to underdo or overdo a severe weather situation. Give a severe weather situation the coverage it deserves without hype or being overly calm.