Linpack is a set of linear algebra routines used frequently in scientific computing for decades so it provides a way to compare new computers to very old ones.
The Cray-1 supercomputer of 1979, sometimes referred to as the "first" supercomputer. It cost $9 million in 1979 dollars ($26 million today), had 1 MegaByte of memory, weighed 5.5 tons, and required 115 KWatts of power. It ran the linpack benchmark at 3.4 Mflops (million floating point operations per second). The iPhone 6+ ran linpack at 180 Mflops on similar data -- the phone actually runs faster on larger matrices. So the iPhone 6 is roughly 60 times faster. And it fits in your pocket.
The Cray-1 was a milestone for weather prediction because it was the first computer that could do a 24-hour weather prediction in less than 24 hours (only a little less so it still wasn't useful at first).