ICAO附件3 <1.4 Use of probability groups>
The probability of occurrence of an alternative value of a forecast element or elements should be indicated, as necessary, by use of the abbreviation “PROB” followed by the probability in tens of per cent and the time period during which the alternative value(s) is (are) expected to apply.
The probability information should be placed after the element or elements forecast and be followed by the alternative value of the element or elements.
The probability of a forecast of temporary fluctuations in meteorological conditions should be indicated, as necessary, by use of the abbreviation “PROB” followed by the probability in tens of per cent, placed before the change indicator “TEMPO” and associated time group.
A probability of an alternative value or change of less than 30 per cent should not be considered sufficiently significant to be indicated.
A probability of an alternative value or change of 50 per cent or more, for aviation purposes, should not be considered a probability but instead should be indicated, as necessary, by use of the change indicators “BECMG” or “TEMPO” or by subdivision of the validity period using the abbreviation “FM”. The probability group should not be used to qualify the change indicator “BECMG” nor the time indicator “FM”.
因此，PROB + TEMPO 连着出现的情况时，表示的是TEMPO出现的可能性，也就是间歇性出现的可能性。比TEMPO更弱。