Archive for Drought

Norbert’s influence on Southwest U.S. to be felt over large area

Very high moisture content for the Desert Southwest over the next three days

Very high moisture content for the Desert Southwest over the next three days

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

 

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Is there an El Nino in the cards for 2012? Perhaps, but not looking as likely.

The mark of a busy hurricane season usually has one element missing from it: El Nino. That is to say, El Nino conditions in the Tropical Pacific tend to suppress Atlantic hurricane activity. This is due mainly to strong upper level winds that cut across the breeding grounds for hurricanes, thus limiting their numbers and intensities. However, one must remember infamous exceptions to this rule such as Andrew in 1992, an El Nino year. There are others as well which remind us of the adage “it only takes one”.

What about neutral years? What defines a neutral year anyway? Basically, when we see the sea surface temperature (SST) anomaly in the Tropical Pacific between .50 Celsius above or below normal, it is a neutral year (ENSO neutral). The scale is not tipped in one direction or another. Easy enough, right?

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Big time rains for the southern states

HPC 5-Day QPF

HPC 5-Day QPF

Get ready for some rain! If you live in eastern Texas, Arkansas and indeed a good deal of the Deep South, you’re in for some wet weather over the next five days. Take a look at the HPC QPF map. It shows the forecast precip over the next five days and a lot of it! The culprit? A potent upper level storm system now situated over southern Arizona and moving in to New Mexico. It will tap the warmer-than-normal Gulf of Mexico moisture supply and really ignite as we continue to move through the week.

While rainy, nasty weather is usually not a welcome event, in this case, I think people will be pleased to see it because of the drought relief it will bring.

U.S. Drought Monitor Map- Sept. 13, 2011

U.S. Drought Monitor Map- Sept. 13, 2011

The last few years have been exceptionally dry for the southern Plains and especially Texas. Looking at the U.S. Drought Monitor maps we can see that at the peak of last year’s hurricane season (Sept. 13 map), nearly the entire state of Texas was experiencing exceptional drought conditions. I have little doubt that this was the reason why TS Don literally dried up as it made landfall in south Texas in July. In fact, the air mass over the western Gulf remained very dry for a bulk of the hurricane season. When TS Lee formed in early September, it too entrained the bone-dry air over the region and actually transformed in to a sub-tropical storm, losing its purely tropical characteristics. I call this phenomenon the Texas Air Layer, similar to the Saharan Air Layer which can dominate the tropical Atlantic with dry, stable air.

Now let’s fast forward to the current winter pattern. We have seen quite an increase in rain fall over a significant portion of Texas and surrounding states due to a favorable storm track and possibly a warmer than normal Gulf of Mexico which supplies more moisture for storm systems. It has also been warmer than normal for the region as it has been for much of the Southeast. This is partly due to a positive NAO or North Atlantic Oscillation which has kept the deep east coast troughs which usher in Arctic Air at bay. Instead of prolonged periods of cold, dry air, the Arctic attacks are brief and the result has been a warmer, wetter winter for much of the southern tier states.

U.S. Drought Monitor Map- Jan. 17, 2012

U.S. Drought Monitor Map- Jan. 17, 2012

You can see the resulting improvements on the latest Drought Monitor map labeled January 17. A remarkable change to say the least and more rain is coming which will further knock down the dry conditions for Texas and elsewhere.

My theory is that if this pattern continues, perhaps the air mass over the southern U.S. and adjacent Gulf Waters won’t be as dry this hurricane season. If this is the case, maybe, just maybe it would open up the western Gulf, Texas included, to more tropical cyclone activity. It makes sense to some extent: if the abnormally dry air mass is gone, due in part to a wetter land mass underneath, then it stands to reason that approaching tropical cyclones won’t dry out nearly as much as we saw in 2011. I think we can all agree that watching Don erode away to nothing as it made landfall was one of most incredible demises to a tropical storm that we’ve ever witnessed. It provided next to no rain fall for the region that it impacted and was all but gone in less than 24 hours after landfall.

We’ll see how this all plays out for the upcoming hurricane season. It may have no bearing at all but I think that drought begets drought and thus more dry air; a kind of feedback mechanism. We know that tropical cyclones are incredibly sensitive to dry air and what we saw over the western Gulf last season was enough to keep the region well protected. I’ll keep tabs on the Drought Index and post a follow up report in the early part of June. For now, enjoy the abundance of rain fall but be mindful of the hazards that excessive rains can bring. It’s all good until somebody gets hurt and we don’t want that.

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