It is often said that the two sounds can be distinguished by context: Unfortunately, the two varieties of shwa are written identically, and pronounced identically in Modern Hebrew; as a result, there is no reliable way to distinguish the two varieties of qamatz when followed by a vowel marked with a shwa.
It should also be noted that there are examples of qamatz qaṭan appearing in open syllables, such as in the plural of שֹׁרֶשׁ ([ˈʃo.ʁɛʃ], "root"), שׇׁרָשִׁים ([ʃo.ʁa.ˈʃim]).
In practice, however, Modern Hebrew words containing a qamatz qatan do add a vav ⟨ו⟩ to indicate the [o] pronunciation; hence the nonstandard (also termed "excessive") spelling תוכנית is common in newspapers and is even used in several dictionaries, for example Rav Milim.
For example, in siddur Rinat Yisrael the vertical line of qamatz qatan is longer.
The following table contains the pronunciation and transliteration of the different qamatzes in reconstructed historical forms and dialects using the International Phonetic Alphabet.
Because of this, the short o (Qamatz Qaṭan) is usually promoted to a long o (holam male) in Israeli writing, written as a vav ⟨ו⟩, for the sake of disambiguation.