I am not sure if I could use the word predict in the context of a scientific forecast.
Does this word have a connotation of guessing, transcendental belief, or some kind of humbug?
And if so, what to use instead?
Prediction is simply saying that something will happen in the future. This may be based on scientific knowledge, experience or something else.
Scientists predicted the earthquake a decade ago.
He predicted he would fail the test because he did not answer half of the questions.
The fortune teller predicted he would get a miracle.
You could say, as this article does, that
This effect is known as gravitational lensing and is one of the predictions of Albert Einstein's general theory of relativity.
There is no humbuggery or New Age flavor that attaches to scientific predictions. They may be proven wrong, but they are always subject to the scientific method.
The word "predict" is routinely used in science, though with a a slightly different meaning than the conventional use.
Normally when we say "predict" we mean that you believe that something will happen in the future. This could be based on some sort of reasonaed analysis: "Noted economist Dr Jones predicts that the stock market will go up 500 points by August". Or it could be supernatural: "The prophet Daniel predicted the fall of Babylon by divine revelation."
The word can be used with this meaning in science. "The geologist predicted an earthquake."
But it can also be used to mean that something is an implication of a theory. "A prediction of Einstein's theory of relativity is that any attempt to measure the speed of light in a vacuum will always give the same result, regardless of the relative motions of the source and the observer."
I say that this is slightly different from the conventional definition because the scientist is not necessarily saying that he believes the prediction to be true. He is saying that IF the theory is true, THEN this result will happen. In real life scientists often formulate theories in which they have little or no confidence, just to have some standard to test against. For example, a scientist might say, I have no idea whether a magnetic field will affect this chemical reaction. So let's formulate the theory that the rate at which the precipitate forms is unaffected by magnetic fields. We could test this theory by, etc.
Scientists routinely talk about the "predictions of a theory", that is, what experimental results we should expect to see if a theory is true. This is commonly used as a test of the validity of a theory: if when we perform the experiments, the predictions turn out to be false, then the theory must be modified or discarded. If the predictions turn out to be true, then the theory may be true. (We can't say that the theory is proven true: it might be that it only appears to be true in some cases.) If we cannot make any testable predictions based on a theory, that theory is said to be weak. It is often said that such-and-such is not a legitimate scientific theory because it does not lead to any testable predictions.
I say this is different from the convetional definition. Someone might reply that people often doubt predictions, that, for example, many people doubt the predictions of psychics. But the difference is that in conventional use, the person making the prediction believes that it is true. (Or at least, claims to believe that it is true. Even the worst charlatan psychic doesn't say, "I don't really believe that this prediction is true. It's just something I made up for fun.")
A fine point, maybe, but I think significant.
While there is much overlap between prediction and forecast, a prediction may be a statement that some outcome is expected, while a forecast is more specific, and may cover a range of possible outcomes. ... Prediction is closely related to uncertainty. (wikipedia)
syn. foretell - prophesy - prognosticate - forecast - presage (Google)
I'd definitely avoid the word in the context of a "scientific forecast". You know, forecast itself brings with it some uncertainty, being a careful choice of a word.
That said, check out also on the same page: 3 Prediction in science