Predicting the weather is a difficult job at the best of times. Weather changes in ways that surprises even experts. But usually getting shocked by changing weather means a family picnic gets a little rained out. No big deal.
That's not what is happening in Texas right now. A massive hurricane called Harvey developed Thursday in the Gulf of Mexico in ways that has shocked experts at the National Hurricane Center (NHC). The storm is now barreling toward the coastal Texas city of Corpus Christi, and should make landfall (reach the shore) by late Friday.
From out of nowhere
Hurricane Harvey was always a storm that the NHC was watching. Still, as late as Wednesday it was merely what they call a tropical depression. This is a large, but non-serious ocean storm that would bring rainfall and winds. In other words, something that your average weatherperson would call a "rainy weekend" and then perhaps suggest cancelling picnic plans. As we said earlier, no big deal.
And yet by Thursday, Harvey whipped itself into a stunning frenzy. Watch the eye form in this video below...
The eye of hurricane Harvey quickly clearing out this evening. A sign of additional intensification. pic.twitter.com/Z1h27McBbU
— Anthony Farnell (@AnthonyFarnell) August 24, 2017
Today it is a Category 2 hurricane, with experts warning that it could become a Category 3 by landfall.
The Saffir-Simpson scale
For an understanding of just how dramatic this leap is, we should look at what hurricane experts use to measure the force of a storm: the Saffir-Simpson scale.
On this scale, a tropical depression, what Harvey was on Wednesday, barely registers. It goes...
- Tropical depression (winds under 62 km/h or 38 mph)
- Tropical storm (winds between 63–118 km/h or 39–73 mph)
- Category 1 hurricane (winds between 119–153 km/h or 74–95 mph)
- Category 2 (winds between 154–177 km/h or 96–110 mph)
- Category 3 (winds between 178–208 km/h or 111–129 mph)
- Category 4 (winds between 209–251 km/h or 130–156 mph)
- Category 5 (winds greater than 252 km/h or 157 mph)
Eventually, we know that this list can just become a bunch of numbers. So think about it like this: in the space of 24 hours, Harvey went from a storm with winds as fast as a car on a neighbourhood street, to one going faster than a car on our speediest highways (Category 1). If it reaches Category 3, it will be the strongest storm to hit the United States since Hurricane Wilma in 2005.
Dealing with the shock
Hurricanes developing over the Gulf of Mexico are nothing new. Coastal towns in states like Texas, Florida, and Louisiana know that the occasional monster storm is part of the deal when you live in what is otherwise such a beautiful part of the world.
But normally hurricanes come with days and even weeks of slowly unfolding warnings. In this case, residents of Corpus Christi (as well as other parts of Texas) only really found out late Thursday about how strong the forecast was. And to be clear, either a Category 2 or 3 hurricane is very powerful. These storms cause major destruction to homes and buildings. And then there's the rain.
This tweet from NHC scientist Eric Blake shows just how unusual this kind of rain could be...
— Eric Blake ? (@EricBlake12) August 25, 2017
At the time of this post, Corpus Christi officials were still advising citizens to not panic and get themselves prepared. Though evacuations aren't mandatory (or demanded by law), they are strongly advising people to leave. Better safe than sorry!
As for what Hurricane Harvey will be when it lands...even the experts can't really say for sure. But places like Corpus Christi, Gavelston, and Houston are tense as they wait to find out. Stay safe, Texas!
See NASA's footage of Hurricane Harvey in this video.