חנמל is a hapax occurring in Psalms 78:47

תהלים עח:מז

יַהֲרֹ֣ג בַּבָּרָ֣ד גַּפְנָ֑ם וְ֝שִׁקְמוֹתָ֗ם בַּֽחֲנָמַֽל: ַיַּסְגֵּ֣ר לַבָּרָ֣ד בְּעִירָ֑ם וּ֝מִקְנֵיהֶ֗ם לָרְשָׁפִֽים:

It is clearly similar to ברד and has destructive power.  HALOT gives “devastating flood” based on an article by Ludwig Koehler (Journal of Biblical Literature, vol. 59 p. 39, 1940), which, unfortunately, is in German.

רשף is a more common word, occurring eight times in TaNa”KH (see below) including once as a name.  HALOT has a long entry on רשף, beginning with a statement of the uncertainty of the etymology, but suggesting that it probably originated as a personal name (as attested in TaNa”KH as well – I Chronicles 7:25).  Its usage in TaNa”KH suggests a sense of fire, e.g. Song of Songs 8:6 רשפיה רשפי אש שלהבתיה.

Quoting from HALOT:

“Both derivations evoke the sinister features which are the essence of this deity, who was worshipped [sic] throughout the Near East.  Rašap was actually identified with the Babylonian god Nergal and can similarly be regarded as a god of the underworld, a god of plagues, and a god of war.”

דברים לב:כד
מְזֵ֥י רָעָ֛ב וּלְחֻ֥מֵי רֶ֖שֶׁף וְקֶ֣טֶב מְרִירִ֑י וְשֶׁן־ בְּהֵמֹת֙ אֲשַׁלַּח־בָּ֔ם עִם־חֲמַ֖ת זֹחֲלֵ֥י עָפָֽר:

חבקוק ג:ה
לְפָנָ֖יו יֵ֣לֶךְ דָּ֑בֶר וְיֵצֵ֥א רֶ֖שֶׁף לְרַגְלָֽיו:

תהלים עו:ד
שָׁ֭מָּה שִׁבַּ֣ר רִשְׁפֵי־קָ֑שֶׁת מָגֵ֬ן וְחֶ֖רֶב וּמִלְחָמָ֣ה סֶֽלָה:

תהלים עח:מח
וַיַּסְגֵּ֣ר לַבָּרָ֣ד בְּעִירָ֑ם וּ֝מִקְנֵיהֶ֗ם לָרְשָׁפִֽים:

איוב ה:ז
כִּֽי־אָ֭דָם לְעָמָ֣ל יוּלָּ֑ד וּבְנֵי־רֶ֗שֶׁף יַגְבִּ֥יהוּ עֽוּף:

שיר השירים ח:ו
שִׂימֵ֨נִי כַֽחוֹתָ֜ם עַל־לִבֶּ֗ךָ כַּֽחוֹתָם֙ עַל־זְרוֹעֶ֔ךָ כִּֽי־עַזָּ֤ה כַמָּ֙וֶת֙ אַהֲבָ֔ה קָשָׁ֥ה כִשְׁא֖וֹל קִנְאָ֑ה רְשָׁפֶ֕יהָ רִשְׁפֵּ֕י אֵ֖שׁ שַׁלְהֶ֥בֶתְיָֽה:

דברי הימים א ז:כה
וְרֶ֣פַח בְּנ֗וֹ וְרֶ֧שֶׁף וְתֶ֛לַח בְּנ֖וֹ וְתַ֥חַן בְּנֽוֹ: