http://revach.net/article.php?id=4300

Section: Parshas HaShavua   Category: Quick Vort
Parshas VaEirah: Vilna Gaon - Barad's Three Pronged Attack
By the Makka of Barad the pasuk says (9:14), "Ki BiPam HaZos Hinini Mishalei'ach Es Kol Mageifosai", this time I will send all my plagues.  What was special about the hail of Barad that is was called, "All of Hashem's plagues", more so than other Makkos?

The Vilna Gaon answers that the Medrash Tanchuma says that Hashem has three battalions that He sends to punish people, fire, wind, and water.  He punished Sidom with fire, the Dor HaMabul with water, and the Dor Haflaga with wind, spreading them to all corners of the world.

In the 10 makkos, Dam and Tzfardei'a were with water.  Arbeh was with wind. Shechin was fire, taken form the ash of the oven.  Barad was fire and water combined with strong winds during the downpour.  This is why Hashem calls it all His plagues as he combine these three elements for the first time in a single Makka.