As Revised Standard Version suggests, the pronoun construction I myself is emphatic in Hebrew.

With outstretched hand and strong arm is a dramatic way of expressing “with all my might” (Good News Translation). See similar constructions in Deut 4.34; 5.15; 11.2; 1Kgs 8.42; Psa 136.12; Jer 27.5; 32.17, 21; Ezek 20.33, 34.

The use of three terms for anger (anger … fury … wrath) is intended to indicate the highest degree of anger: “you will feel the full heat of my anger” (Die Bibel im heutigen Deutsch). In some languages it will be impossible to accumulate as many as three terms for anger, and in other instances it will be more emphatic to use only one or two similar terms, even when three are available.

Quoted with permission from Newman, Barclay M. and Stine, Philip C. A Handbook on Jeremiah. (UBS Helps for Translators). New York: UBS, 2003. For this and other handbooks for translators see here .