It is rare for a tropical storm or hurricane to impact the weather for the Southwest U.S. but it does happen. Going back to 1939 and then again in 1976 and 1997, there have been infamous storm events that brought flooding rains to areas that are not used to such high precip events. It looks as though Norbert will be added to that list.
First of all, let me say that I am in Phoenix, AZ this morning after having traveled here from Houston where I flew in on Friday.
I am working with Amateur Radio operator and friend to HurricaneTrack.com, Kerry Mallory. He has been my wheels, so to speak and we have covered some serious ground since Friday afternoon.
We are out here because of the serious threat of flooding as a result of monsoonal flow and the influx of moisture from what was once category three hurricane Norbert. This situation is unique and is quite different for us than any other hurricane related field mission we have undertaken.
Tropical cyclones have the ability to drop a tremendous amount of rain. Inland flooding from excessive rain fall is often overlooked by the public as being a potential threat. Wind and storm surge grab the headlines until the rains begin to fall and add up – by then, it’s usually too late to react.
In the case of the Desert Southwest, it’s not a matter of seeing ten to twenty inches of rain. In this case, just a few inches is all it will take to cause incredible flash floods to occur which puts property and lives at risk.
The main culprit will be the flow of moisture from Norbert as we get later in to today and through the next few days. Areas from southern California to Arizona, New Mexico, Nevada and in to Utah are under the threat of flooding rains and serious flooding.
One of the more difficult tasks of the NWS out here is to know which areas could be most impacted. The geography of the region makes it tough to predict precisely where heavy rains could fall. Heating of the day, mountain ranges and other factors make it a challenge to convey to the public who is most at risk. As such, the NWS has done a great job in putting out public information statements and even YouTube videos explaining the threat from this flood event.
As I have read the area forecast discussions, it is remarkable to note how much water is available in the atmosphere compared to normal. In some cases, as much as 300% the normal water available in the air column is forecast to be present – giving ample fuel for potentially very heavy rain.
The most vulnerable areas appear to be the mountains and hill sides that have what are called burn scars on them. These are left over scar areas from recent (or not so recent) forest fires. The soil is like pavement with ash and other debris compacted in with little to no vegetation left behind. It only takes moderate rain for a little while to send water down these burn scars, filled with debris as it flows in to streams and otherwise dry washes. The result can be deadly and people caught unaware can be buried by these debris flows.
As I mentioned, Kerry and I are in Phoenix today. We will be on the lookout for developing thunderstorms throughout the day and will try to get to areas where heavy rain is likely to fall. Our goal is to document the event using some of the same technology we utilize during storm surge along the coast. We don’t want to be caught in a flash flood ourselves, so using remote, unmanned cameras will help to keep us safe while we capture video of flooding.
We can also post information to social media to help people in the region keep up with what’s going on in near real time. Video clips can be posted to our Instagram feed in no time at all, it’s amazing what we can do these days, even in the middle of the desert! We’ll also post pics and information on conditions as we encounter the storms later today and tonight.
Believe it or not, the rain threat extends up in to Utah and that is where we plan to be by later tonight. Reading the discussions for the southwest part of the state, it looks serious. We’re talking about widespread flooding a distinct possibility in parts of Utah tonight and tomorrow. This presents us with a unique situation to both try and observe and research the event while remaining safe. I am no stranger to rain but flash floods in canyon lands is totally alien to me. Again, the use of unmanned cameras will be paramount to documenting the effects from incredible viewpoints.
We plan to stream our field work live on our Ustream channel throughout the day today. Follow along at ustream.tv/hurricanetrack
If you live in the region that is forecast to be affected by this unusual event, keep aware of rapidly changing weather. It’s going to be an interesting and potentially dangerous few days out here and we hope to document it and learn from it for future preparedness when the inevitable happens again.
Oh yeah, the Atlantic Basin is of no concern right now, so at least there’s that.
I’ll post another blog tonight from St. George, Utah.
M. Sudduth 11:51 AM ET Sept 7