Here we encounter yet another example of the idiocy of the lexicography of LS2. This word does not mean storm. It is rather the word ܥܪܡܘܬܐ that provides the semantics of a forceful storm while stwˀ simply tells us it is a winter one.
The example in the "Bauer-Meissner papyrus" has not been generally recognized since it appears to have prefixed "d_" after the same word spelled "zy"; but the latter is of course a literary spelling of a form that had almost certainly already shifted to "d" in pronunciation, so we take the expression to be a fixed expression "wintery, late crop".