The expression (idiom?) jam nunc appears several times in the Vulgata. So far I've seen two common translations. One is that of "now presently". For instance, Exodus 9:19:
(Latin) Mitte ergo jam nunc, et congrega jumenta tua, et omnia quae habes in agro ...
(English, Douay-Rheims) Send therefore now presently, and gather together thy cattle, and all that thou hast in the field ...
Another translation is "here and now". For instance, 1 Samuel 14:33:
(Latin) Nuntiaverunt autem Sauli dicentes quod populus peccasset Domino, comedens cum sanguine. Qui ait : Praevaricati estis : volvite ad me jam nunc saxum grande.
(English, Douay-Rheims) And they told Saul that the people had sinned against the Lord, eating with the blood. And he said: You have transgressed: roll here to me now a great stone.
"Nunc" always means the literal present or "now"; the other use of "now" is usually translated "iam".
But how are the two together to be normally understood? Is there a rule for this? Is this phrase perhaps an idiom?