Another Watermelon and a Monstrous Pumpkin (?) Vine

I hadn't seen this one before and suddenly it was a real mini-watermelon.  I'd guess there are about 15 at this point, from 1/2" to 2" diameter.  I believe this is the point that they need a lot of water so I've been watering them in the evenings.  Weather.com, now with access to weather balloons only because the powers that be in Washington decided last year that we no longer need to have access to information from weather sattelites, has been reporting a 79% chance of rain every day for the past week and we got nothing.  Then, this morning, exactly when it said there was a 0% chance of rain, it started to rain.

I remember when I was growing up people made fun of weather reporters because they were ALWAYS wrong.  Then, sometime in the 80s, every rinky dink TV station got access to the "Dopplar Radar" (whatever that is) and the weather reports became the most scientifically reliable part of the news, while everything else turned into entertainment.  (In the immortal words of KTLA's Hal Fishman, "I guess that's news.")  Now we are back in the 1970s in more ways than one and I don't like it. 

At the very back of the yard, between our stone wall and a raised garden bed a vine of somt sort sprouted up from where we used to have our compost pile.  I have no idea what it is but it is larger and more aggressive than any plant I've ever grown before. You can't see it well from this picture, but it is about 2' tall, and runs along the wall for about 6'.  The leaves are the size of dinner plates and yesterday one blossom appeared, and it is larger than my hand:

And here it is growing over and between two raised beds, and taking over the entire path I need to use to get to my strawberries and tomatos.  To be honest, I'm slightly afraid of it.  Its stems are 2" thick and too tough to bend to comply with my trellis supports--it's going to do what it's going to do and that's all there is to it.  Even the ground hog leaves it alone.