Grammar:Tutorial/Jussivus and cohortativus
According to this book imperfect may also mean a modality, such as necessity or desirability.
According to the opinion of Victor Porton, that interpretation is theologically dubious, because imperfect has its own meaning and adding other meanings may contradict the the principle of literality in interpretation of Bible.
1st person of imperfect with added suffix ה is called cohortativus.
Its meaning in examples: אשלחה (Let I send), נשלחה (Let us send).
This work needs more thorough examination of jussivus. See §§106, 158, 166 in this book.