Saturday, January 23, 2010

Weather got you down? Interview with Greg Smith from The National Weather Service

Repost of an interview from early 2009 

Add the elements to your story, how to make it real. Special Guest: Greg Smith National Weather Service will answer any questions for your adventure, suspense writers that want to had the elements to your story.

A little bit about our Guest: Greg has spent 27 years with the national weather Service. For eight of those years he served in the capacity of a meteorologist, responsible for preparing and disseminating aviation, agricultural, and public forecasts at a Weather Forecast Office (WFO). WFO’s have the primary responsibility, as designated by Congress, to issue warnings and watches as they relate to weather or hydrologic situations. The past 19 years he served in a River Forecast Center (RFC) where the primary responsibility is to provide short-term river forecasts and longer seasonal water supply forecasts for the protection of lives and property and to enhance the nation’s economy. In this role in the RFC, forecasters are responsible for analyzing current weather and precipitation amounts using the latest technology such as Doppler radar, importing this information into river models, then analyzing the output to determine whether river levels may approach dangerous levels. This information is provided to WFO’s where flood related warnings might be issued based on the guidance form the RFC’s. His educational background includes a Bachelors degree in meteorology and Masters in Geography. 

MARY: Greg thank you for taking the time out of your busy schedule for a short interview on the elements. And how we can add them to our stories. First, is there anything you’d like to add to your bio? 

Greg: I think that’s really about it as far as the bio goes. Perhaps the most interesting weather phenomena I’ve experiences was in Grand Junction Colorado. A thunderstorm came over the area and dropped what I thought was hail. I picked up the hail and it was cold, but warmed in my hands. It never melted. It turned out to be small white rocks. Most likely what had happened was these were picked up in some type of strong updraft. Given the weight of them it may very well have been a funnel cloud or possibly a tornado. As the storm dissipated it dropped the super cooled rocks. It was pretty cool at the time.

MARY: What is the most common element, or situation a person finds themselves stranded? And how would they survive?

Greg: From a weather perspective, flooding is the most common killer, and the most costly in the United States. More people find themselves dealing with flood dangers than any other weather element. A lot of people perish in floods needlessly by not avoiding the situation in the first place, or by trying to escape the water improperly. Flooding also takes on many forms, including flash flooding, coastal flooding (associated with a wind driven storm surge or tsunami), urban flooding (due to the creation of impervious surfaces) that can cause street and basement flooding, and ice jams (that block river flows). River flooding is more inevitable and just a natural part of the life of a river. The worst river flooding usually occurs from torrential rains associated with dying hurricanes or tropical storms. Runoff from snowmelt, especially if accompanied by heavy rainfall, results in some fairly significant flooding.

When caught in a flood time to act is usually very short. Some situations are simply not survivable which is why we stress preparation and what we like to call “situational awareness”. If caught though, the number one move should be to try and get to higher ground. If trapped by fast moving floodwaters, stay put if all possible and wait for the waters to recede. Six inches of moving water can sweep a person off their feet. Two feet of water will move most vehicles. One foot of water moving at 6-12 mph will move 1500 lbs. So 2-3 feet will move most vehicles. The other unknown factor is that the streambed, whether it be a road surface or whatever, may be undermined or washed away and you can’t see it. Close to half of all flood deaths occur in vehicles when people try and drive through flooded areas.  If a person is ever swept away in a flood, they should keep their feet pointing downstream as best as they can. It is better to hit debris, rocks, etc. with your feet than your head. This also allows you to perhaps spot an out, such as a tree, something floating on the surface, or an eddy or area where you might be able to escape.

MARY: What exactly is a flash flood? Where would this be most common? And what would a person need to do to survive? Is there any warning?

Greg: The most straightforward definition is the onset of a large volume of water in a very short duration. The NWS has loosely used a 6 hour time threshold to determine the onset of a flash flood. Flash flood can occur just about anywhere, but most commonly you will find them where geology, geography, and topography combine to form an ideal setting. One such place is Austin Texas, and here’s an example of how these things work together.

Geography – Austin lies in an area where it receives large sources of moisture from the Pacific Ocean and Gulf of Mexico. As a result very heavy rainfall occurs in this part of the world.

Topography – Austin is near an area called the “Hill Country”. Water runs downhill and runoff quickly moves into the area where Austin is located. The Balcones Escarpment also acts to enhance precipitation rates as it creates additional lift to storms moving into the area. As air is lifted it cools and can hold less water, so this adds to heavy precipitation rates. Mountains and large sloping surface features that are perpendicular to the air flow or storm movement cause these systems to lift, cool, and reduces their ability to hold moisture, thus – heavier rainfall.

Geology - Limestone and thin soils exist in much of this area and it doesn’t absorb water all that quickly.

All these things combine to make Austin very susceptible to flash flooding. Other areas include the desert southwest. In these areas the hardened sandstone is very impervious to runoff, and the narrow canyons funnel the water. Basically “walls of water” have been observed moving down stream, in some instances they move for many miles, over several hours, far away from the original storm.

To survive these you need to arm yourself with knowledge beforehand as to whether you will be in a flash flood prone region and if the weather is conducive to heavy rainfall. If a flash flood does occur the only thing you can do is to climb to higher ground. If your are not in a area where you can do this, chances of survival are minimal. Flash floods occur very rapidly in these areas.. When in a flash flood prone region, the sound of distant thunder is a good warning to adhere to. Rain does not need to be occurring where you are standing.

Warnings are issued but because these situations develop quickly, the lead time may not be enough to react. In many cases, people out in the country, may or may not hear any such warning. 

MARY: I live in Utah, this time of year we hear a lot about Avalanches in the news. What conditions would a skier or hiker need to be aware of to avoid one? Also, what equipment is it wise to have on your person to avoid disaster if caught in one?

Greg: I’m not an expert on avalanches and not qualified to speak of them extensively, but I work only a few feet away from several people who are. They are with the Utah Avalanche Forecast Center and I am going to give you a link to one of their web pages with some great information. There is a lot of good advice here and I also copied an excerpt from that page and pasted it below. Note also that avalanches occur as large slabs of snow, one slab of snow, with particular properties of density, weight, etc., that slides over another layer of snow. Dry slabs cause most fatalities.

Snow is a lot like people. It doesn't like rapid change. (Raise taxes slowly enough and no one notices.) Dry slab avalanches occur when the weak layer beneath the slab fractures, usually because too much additional weight has been added too quickly, which overloads the buried weak layer. Snow is very sensitive to the rate at which it is loaded or stressed. Two feet of snow added over two weeks is not a problem. Two feet of snow in two days is a much bigger problem. Two feet of snow in two hours is a huge problem. (Wind can easily deposit two feet of snow in two hours.) Then, finally the weight of a person can add a tremendous stress to a buried weak layer, not in two hours, but in two tenths of a second-a very rapid change. That is why in 90 percent of avalanche accidents, the avalanche is triggered by the victim (or someone in the victim's party). Wet slab avalanches occur for the opposite reason. Percolating water dissolves the bonds between the snow grains, which decrease the strength of the buried weak layer. 

MARY: If my hero & heroine ended in a ditch in a blizzard and they had to walk a cabin...if the temps were dipping below zero, how long could they stay out in the elements without hypothermia setting in.  How about frostbite? 

Greg: Hypothermia occurs when the body temperature drops below about 95 degrees Fahrenheit.  How long this might take depends upon the condition of the person at risk since everyone reacts to cold differently. Because of this there’s no real reliable table or temperature threshold. Elderly or very young individuals are more susceptible, as are thin people vs. heavier individuals.  Those with inadequate food or those who have been drinking or on drugs will also be more susceptible to hypothermia sooner since their body is not efficiently generating heat.  Also keep in mind that people lose body heat in water about 25 times faster. So, if in cold water the time to reach hypothermia is much quicker. It can occur very quickly, in a matter of minutes.

Hypothermia can actually occur at temperatures above freezing, even up to around 40 degrees. If you are wet, are cold, in cold rain, sweat and then get chilled etc. hypothermia is possible. Whenever you shiver (due to the cold), your body is in a very early stage of response to hypothermia and a lower body core temperature.

Frostbite will occur when tissue freezes and blood flow stops to that area. On exposed skin frostbite occurs and the wind chill does play a role. I’ve listed some wind chill temperatures (or air temperatures without the wind) that are associated with frostbite. Again, it may depend on the individual.

00F to -190F    Exposed skin can freeze within 5 minutes.

-200F to -690 Exposed skin can freeze within 1 minute.  Outdoor activity becomes dangerous.

-700F and below  Exposed skin can freeze in 30 seconds.

Hopefully your hero and heroine have enough clothing to layer. Layering clothes traps pockets of air and acts as excellent insulators in cold weather. When trapped in winter we’ve always advised people to stay with their vehicle. It’s a source of heat and protection. Most people leave due to panic and or lack of food. It’s always good to keep extra food in a vehicle when traveling in remote regions in winter. If you stay with your car, it’s also important to get out and remove the snow from the tailpipe. Unfortunately people forget to do this and they succumb to CO poisoning. 
MARY: Katrina is still on the minds of people in the South. What would a person need to do to survive a category 5 hurricane? Actually, what is the most common category? And what are normal precautions people make who live in hurricane zones? 
Greg: A category 5 hurricane by all rights is not survivable.  I would say to anyone facing a cat 5 is to either leave, or prepare to meet your maker. Don’t expect to survive, odds are against you. Those that do survive beat incredible odds and are very lucky.  Folks forget, that while Katrina hit CAT 5 just off the coast, it weakened to CAT 3 just as it hit the mainland. That said, any hurricane warrants evacuation if that is possible. Other than that you need to get inland, away for the coast and potential storm surge. You also need to be in a strong building but avoid highest floors since that’s where strongest winds occur. Do not take shelter in a temporary structure or mobile home. Get away from glass doors and windows. Stay in an interior room, closet, or hallway.

Prior to hurricanes most folks in these areas have an evacuation plan, they have storm shutters or board up their windows, extra food, water, fuel is stored. They have battery powered light sources and radios. They are advised to turn off all utilities, in particular gas, prior to the onset of the storm. There are materials to secure roofing. Trees and shrubs that might become airborne in the winds are trimmed. Anything outdoors that could become airborne is secured or taken in.

Between 1850 and 2006 the greatest number of hurricanes that have hit the US mainland were Category 1 hurricanes, followed by Cat 3, then Cat 2, Cat 4, then Cat 5. 

MARY: The only thing left that I can think of is a Tornado. I’m sure we’ve all seen Twister, and know what a funnel cloud looks like. Is there anything interesting you could tell us that we may not know that we could add to a story? 

Greg: Twister was a fun movie, but there was quite a bit there that was unrealistic. Most storm chasers can’t get within 5 miles of a tornado. Debris flying around and the danger associated with these storms is simply to great. In addition accurately determining where one is going to develop (at least at the scale in the movie) isn’t that easy. Most twisters last less than 10 minutes although some can last over an hour. Most tornadoes travel from southwest to northeast.  Some other interesting facts, 70% of all tornado deaths occur in only 2% of all tornadoes while weaker tornadoes account for 69% of all tornadoes accounting for less than 5% of all deaths. I’ve got a kick out of the cows floating around in those twisters. There have been survivors of tornados in Wichita Falls Kansas that lost arms and legs. Here’s some other tornado tidbits:

In the southern states, peak tornado occurrence is in March through May, while peak months in the northern states are during the summer.

Note, in some states, a secondary tornado maximum occurs in the fall.

Tornadoes are most likely to occur between 3 and 9 p.m. but have been known to occur at all hours of the day or night.

The strongest tornadoes have rotating winds of more than 250 mph.

Tornadoes can be one mile wide and stay on the ground over 50 miles,

Tornadoes may appear nearly transparent until dust and debris are picked up or a cloud forms within the funnel.
The average forward speed is 30 mph but may vary from nearly stationary to 70 mph. 
Invironmental clues – look out for:

  • Dark, often greenish sky
  • Wall cloud
  • Large hail
  • Loud roar; similar to a freight train
MARY: Is there anything I haven’t asked that you may think an author would find interesting to use?

Thank you Greg Smith for visiting with me. I appreciate all the information.


Liz L. said...

Intriguing. I live in Texas close to Tornado Alley. Although I have never actually been in a tornado, I have been caught in straight line winds and it's scary. We have a lot of tornado warnings here and I've even huddled in a hallways at a restaurant during a horrific storm, but thankfully, no real damage was done.

Thanks Greg and Mary for enlightening us about this interesting topic.

Mary said...

Glad you've never had to leave through a bad one. I have a son who lives in Austin!