Frequently Asked Questions

Is this a year-long or annual prediction?

Neither. The new product is a series of 90-day outlooks produced in one-month steps. The series begins with the outlook for the next three months (for example, February, March, and April), followed in turn by a separate 90-day outlook for the period beginning one month later than the first 90-day outlook (to continue the example, March, April, and May). A series of thirteen 90-day outlooks will be issued around the middle of the preceding month.

Can I use this product to help me schedule an outdoor event when we'll have nice weather?

No. The outlooks do not attempt to accurately predict weather for any one given day or location. The methods used to produce each outlook will at best offer insight into longer-term expected trends (such as drier or wetter than normal for a season in a particular region of the country).

How is this different from the Farmer's Almanac?

The two do not compare. The NWS product does not attempt to offer precise predictions of temperature and rainfall in outlook products or outlook predictions.

How do I know what is "normal" weather where I live? (above "normal", below "normal")

Normals for your area of residence are typically given in weather reports provided by the news media. Your nearest Regional Climate Center or National Weather Service Office can also provide a gauge of what the normal climate pattern is for your area.

Who will find this prediction useful?

Governments and industries which already use a variety of means to anticipate future weather patterns for making decisions (transportation managers who must determine how much road salt to purchase for use in winter, farmers who are looking to get the most yield out of their arable land). The predictions will not be useful for anyone trying to plan an event for a specific date.

What kind of information will be included in the outlooks?

The outlooks will have information about temperature and precipitation for different regions of the country. The outlook will compare the anticipated temperature and precipitation to normals for a given region, and categorize the anticipated levels as above normal, normal or below normal.

What elements go into a long range outlook?

Sea surface temperature patterns, upper atmospheric winds, and historical weather patterns.

Are these outlooks produced using the same techniques as the 30- and 90-day outlooks we are accustomed to looking at?

No. The techniques and our methods for using them are different. The techniques we use are both statistical (the canonical correlation analysis and the optimal climate normals) and dynamical (coupled ocean-atmosphere model). Even more importantly, we strictly require that a prediction of climatological probabilities be used in regions where the techniques we use have marginal accuracy.

Are the predictions more reliable for different times of the year? Is a prediction for 8 months away "less accurate" than a prediction for 3 months away?

Briefly, the January, February, March outlooks and the July, August, September outlook are the highest in terms of reliability or "skill". The April, May, June outlook and the November, December, January outlook have the lowest skill. As most of us know from personal experience, these are "transition" months between seasons when the weather can wildly fluctuate from day to day. The skill of outlooks also varies between regions of the U.S. It is quite possible that a prediction for a period eight months in the future may actually be more reliable than an outlook for the next 90 days. Your Regional Climate Center can give you detailed information about these aspects of the skill of the outlooks.

Is there any difference in the reliability of temperature vs. precipitation outlooks?

Yes. At almost all prediction ranges, U.S. temperature predictions have turned out to be substantially better (on average) then U.S. precipitation predictions. This is because temperature is continuous (at each point there is always a temperature value Ð the temperature varies "monotonically" from place to place). Precipitation, on the other hand, is discontinuous, (at each point there is either zero precipitation or some amount Ð precipitation does not vary smoothly from one place to the next).

I have to make a decision involving millions of dollars. Weather is an important input to my decision process but it is not the only input. How reliable are these predictions? How much weight should I give them in my decision making process?

Your decision can be weighted appropriately by combining the known skill of the outlook (available from your Regional Climate Center) with the appropriate mathematical decision-making tools. Please have the climatologist/meteorologist in your company check with the RCCs or contact a private meteorological firm skilled in these techniques.

I live in Idaho. I understand these outlooks are less useful in my area. Can you explain why that is?

The accuracy of any outlook varies both regionally and seasonally. In some places, for example, coastal areas, the ocean exerts a stabilizing influence on the climate, making it less changeable, or less "noisy," with respect to atmospheric disturbances at seasonal time scales. In those regions, the atmosphere is also more predictable on long-ranges for a larger portion of the year, since slow climate variations which produce relatively small, but persistent anomalies, stand out better in the data.

Regions which are far from coasts, and especially in the mountainous western section of North America, including large portions of Idaho, are more subject to rapid and repeated short-term climate variations. Unfortunately, many of these variations are, by nature, not predictable. Rather, they contribute to the climate noise, often making any small, persistent anomalies which do occur indistinguishable from the climate noise.

Can you explain, in layman's terms, how sea surface temperatures in tropical areas affect the weather patterns in the United States?

The answer can be put into layman's terms, but is not so simple.

The sea surface temperature near the equator in the Pacific Ocean changes little from day-to-day, week-to-week, or even month-to-month. This means that sea-surface temperature anomalies, i.e., the sea-surface temperature which is warmer or colder than the 30-year average for the location and date, lasts for months, seasons or even years. Sea-surface temperature in the tropics is closely related to the occurrence of large thunderstorms throughout the tropics. These storms transfer the warmth from the ocean surface into the atmosphere overhead.

At an average of every three to five years, ocean surface temperatures in the equatorial central and eastern Pacific become abnormally warm. The abnormal warming in the eastern Pacific often begins in mid to late December and peaks during the northern spring.

During El Niño episodes, abnormally low pressure is observed in the eastern tropical Pacific and abnormally high pressure is found over Indonesia and northern Australia. The normal pattern of tropical cloudiness and precipitation is also disrupted. Rainfall that normally falls over Indonesia shifts eastward over the abnormally warm ocean waters of the central equatorial Pacific.

The effect of El Niño upon the global atmospheric circulation together with the location of the United States just to the northeast, make the U.S. particularly vulnerable to increased storminess over its southern sections during El Niño. Another effect of El Niño is reduced storminess over the northern U.S., along with unusual warmth and dry conditions.