1. Tell me what is a tropical cyclone?
A tropical cyclone is defined as a non-frontal low pressure system of synoptic scale developing over warm waters having organised convection and a maximum mean wind speed of 34 knots or greater extending more than half-way around near the centre and persisting for at least six hours.
Every cyclone is unique varying according to a number of factors including life cycle, intensity, movement, size and impact (wind, storm surge and flooding).
2. Explain me what about tsunamis?
A tsunami is a series of ocean waves with very long wavelengths (typically hundreds of kilometres) caused by large-scale disturbances of the ocean, such as:
earthquakes
landslide
volcanic eruptions
explosions
meteorites
These disturbances can either be from below (e.g. underwater earthquakes with large vertical displacements, submarine landslides) or from above (e.g. meteorite impacts). They are not caused by tropical cyclones.
3. Tell me why and how are cyclone names chosen?
Tropical cyclones are named to provide ease of communication between forecasters and the general public regarding forecasts, watches, and warnings. Having a name also raises the profile of the cyclone heightening the public's awareness. Since the storms can often last a week or longer and that more than one can be occurring in the same region at the same time, names can also reduce the confusion about what storm is being described.
The Bureau of Meteorology maintains a list of names (arranged alphabetically and alternating male and female). A name remains on the list until its corresponding cyclone severely impacts the coast (e.g. Larry and Vance). The name is then permanently retired and replaced with another (of the same gender and first letter). It can take over 10 years from the time a name is put on the list to when it is first used to name a cyclone.
4. Explain me what is the eye and eye wall?
The circular eye or centre of a tropical cyclone is an area characterised by light winds, fine weather and often clear skies. The eye is the region of lowest surface pressure
The size of the eye varies from one cyclone to the next ranging from 10 km to over 100 km. The eye diameter of severe cyclones off the northwest coast tends to be about 20 to 40 km, and are typically smaller than those in some other parts of the world such as the north Pacific. The eye size of Tracy (Darwin, 1974) was just 12 km across. Rosita (Broome, 2000) only had an eye diameter of 20 km.
5. Tell me how did you become interested in the weather?
It really goes back to my childhood and growing up in the Midwest watching thunderstorms. Going back to when I was 7 or 8 we had a big sliding glass door and I would watch the lightning and it was fascinating.
6. Tell me how has technology improved to make forecasting more accurate?
It's just the data that's available now. When I started there were two basic models that you could get every 12 hours. Now there are more models available that crunch the data down.
7. Tell me do you go out and do any storm chasing?
One of the things I wish I could do more of is being out there watching storms develop.
8. Explain me what does your work entail?
In simplest terms my job consists of two things.
1) making the forecast and
2) giving it out!
9. Explain me how did you get started?
I began my broadcasting career as the weekend weather anchor in Cheyenne, Wyoming at KGWN-TV.
10. Tell me how much money did/do you make starting out as a Meteorologists?
Granted it has been a decade and a half, but I made $10 dollars/hour at my first job!
11. Please explain what is most rewarding?
Knowing that I can provide some guidance to an individual or a family and occasionally some potentially life saving information makes it all worth it. For example, earlier this year we had some rare (for Colorado) early morning tornadoes that damaged several communties on the eastern plains. I didn't go home until 6:30am and was totally exhausted but received this from a viewer the next day:
12. Tell me what else would you like people to know about your job/career?
There are so many facets to being a television meteorologist and the pace of the newsroom so fast, that they days just fly by!
The severity of a tropical cyclone is described in terms of categories ranging from 1 (weakest) to 5 (strongest) related to the maximum mean wind speed as shown in this table.
Note: corresponding approximate wind gusts and central pressure are also provided as a guide. Stronger gusts may be observed over hilltops, in gullies and around structures.
14. Tell me how are tropical cyclones different from tornadoes?
While both tropical cyclones and tornadoes are atmospheric vortices, they have little in common. Tornadoes have diameters on the scale of hundreds of metres and are usually produced from a single thunderstorm. A tropical cyclone, however, has a diameter on the scale of hundreds of kilometres and contains many thunderstorms. Tornadoes are primarily an over-land phenomena as solar heating of the land surface usually contributes toward the development of the thunderstorm that spawns the vortex (though over-water tornadoes have occurred). In contrast, tropical cyclones are purely an oceanic phenomena - they die out over-land due to a loss of a moisture source. Lastly, tropical cyclones have a lifetime that is measured in days, while tornadoes typically last on the scale of minutes.
The Bureau of Meteorology uses a 10 minute averaging time for reporting the sustained (i.e. relatively long-lasting) winds. The maximum sustained wind are the highest 10 minute surface winds occurring within the circulation of the cyclone. These surface winds are those observed (or, more often, estimated) to occur at the standard meteorological height of 10 m having an unobstructed exposure.
Gusts are a wind peak lasting for just a few seconds. Typically, in a cyclone environment the value for a peak gust is about 25 % higher than a 10 minute sustained wind. Barrow Island and Mardie sustained wind and wind gust profile during TC Monty (2004).
16. Explain me how do tropical cyclones form?
For a cyclone to form several preconditions must be met:
☛ Warm ocean waters (of at least 26.5°C) throughout a sufficient depth (unknown how deep, but at least on the order of 50 m). Warm waters are necessary to fuel the heat engine of the tropical cyclone.
☛ An atmosphere which cools fast enough with height (is "unstable" enough) such that it encourages thunderstorm activity. It is the thunderstorm activity which allows the heat stored in the ocean waters to be liberated for the tropical cyclone development.
☛ Relatively moist layers near the mid-troposphere (5 km). Dry mid levels are not conducive for allowing the continuing development of widespread thunderstorm activity.
☛ A minimum distance of around 500 km from the equator. Some of the earth's spin (Coriolis force) is needed to maintain the low pressure of the system. (Systems can form closer to the equator but it's a rare event)
☛ A pre-existing disturbance near the surface with sufficient spin (vorticity) and inflow (convergence). Tropical cyclones cannot be generated spontaneously. To develop, they require a weakly organised system with sizeable spin and low level inflow.
☛ Little change in the wind with height (low vertical wind shear, i.e. less than 40 km/h from surface to tropopause). Large values of wind shear tend to disrupt the organisation of the thunderstorms that are important to the inner part of a cyclone.
Having these conditions met is necessary, but not sufficient as many disturbances that appear to have favourable conditions do not develop.
17. Tell me what's the weather going to be like this summer/winter?
Information about the likelihood of it being hotter/cooler or wetter/drier than normal can sometimes be calculated using seasonal forecasting techniques. The techniques tend to be most reliable for other parts of the world than the UK - in the tropics especially over the oceans.
18. Tell me how much data do you look at when developing a weather forecast?
On a clear day when it's really simple, you can put one together in 30-40 minutes. On a day like today (hot and humid), you can be looking at things for hours. If I know there's a big event coming, I'll spend three or four hours a day easy looking at it before I get to work.
The pressure I get I put on myself. I don't get pressure from my bosses, and I don't get pressure from viewers. It's a pride thing.
The comment that you hear all the time, and it's in jest most of the time, is 'Hey, you've got the best job because you only have to be right 50 percent of the time' or they'll ask me when's the rain coming.
21. Explain me how do you make money/or how are you compensated?
Like most television news/weathercasters I have a contract for an agreed upon length of time for an agreed upon salary. In my opinion television news contracts exist to protect the employers more than anything else. For example, if I chose to work at a competing station at the end of my contract, I'm unable to do so for a certain length of time.
Not so much the right or wrong. The complaints we get are 'Why are you cutting into "Survivor" when there's a thunderstorm warning in Spencer when I live in Norfolk?'
23. Explain what is the life-cycle of a tropical cyclone?
Tropical cyclones have a distinct life cycle. For cyclones that reach at least severe (category 3 or higher having wind gusts of at least 165 km/h) the life-cycle may be divided into four stages. For non-severe cyclones, their development is constrained by one or more of a number of factors such as being located in an unfavourable atmospheric environment, movement over cooler water or making landfall.
1. The formative stage
On satellite images the disturbance appears as an unusually active, but poorly organised, area of convection (thunderstorms). The circulation centre is usually ill-defined but sometimes curved cumulus cloud bands spiralling towards an active area of thunderstorms indicate the location of the centre. Initially the amount of convection near the centre is dependent upon the normal diurnal cycle of tropical convection, increasing overnight and subsiding during the day. As development occurs the convection persists throughout the day. The strongest surface winds may be well removed from the centre, tend to occur in disorganised squalls and are often confined to one quadrant, for example the northwesterly monsoon winds to the north of the centre. Apart from local squalls the maximum wind is usually less than gale force. When formative stage tropical cyclones move inland they produce little or no damage on landfall but are often associated with heavy rain and sometimes flooding over northern Australia.
2. The immature stage
In this stage the area of convection persists and becomes more organised. Intensification occurs simultaneously. The minimum surface pressure rapidly drops below 1000 hPa and convection becomes organised into long bands spiralling inwards. Gale-force winds develop with the strengthening pressure gradient, and the maximum winds (which now may be storm-force or more) are concentrated in a tight band close to the centre. The circulation centre is well defined and subsequently an eye may begin to form. In satellite images several well organised curved bands of active convection may be seen spiralling in towards a central dense mass of clouds covering the focal point of the banding, or surrounding the centre. The eye (if it exists) may be masked by a canopy of cirrus cloud, which itself may contain curved striationsassociated with the outflow at the top of the tropical cyclone. The immature tropical cyclone can cause devastating wind and storm surge effects upon landfall, although damage is usually confined to a relatively small area. In this stage of development very rapid intensification can occur and the associated structural changes observed when the cyclone is under radar surveillance can sometimes be confusing.
3. The mature stage
During this stage the tropical cyclone acquires a quasi-steady state with only random fluctuations in central pressure and maximum wind speed. However, the cyclonic circulation and extent of the gales increase markedly. Asymmetries in the wind field may also become more pronounced. In satellite images the cloud field is highly organised and becomes more symmetrical. The more intense cyclones are characterised by a round central dense overcast containing a well-centred, distinct round eye. The surrounding convective bands are tightly coiled and quasi-circular. Typically a cyclone spends just a day or so at maximum intensity until it begins to weaken, unless the cyclone remains in a highly favourable environment.
4. The decay stage
The warm core is destroyed during this stage, the central pressure rises, and the belt of maximum wind expands away from near the centre. Decay may occur very rapidly if the system moves into an unfavourable atmospheric or geographic environment, but sometimes only the tropical characteristics are modified while the cyclonic circulation moves on to higher latitudes.
24. Explain how does the amount of damage caused by a cyclone increase as the wind speed increases?
As wind speed increases the power of the wind to do damage increases exponentially. Hence a category 5 severe tropical cyclone (with wind gusts > 280 km/h) has the potential to do around 250 times the damage of a Category 3 severe tropical cyclone (with wind gusts of 165 km/h). This underscores the importance of the category system.
For historical reasons tropical cyclones are called different names in different parts of the world. The terms hurricane and typhoon are regionally specific names for a severe tropical cyclone (sustained winds of more than 118 km/h (64 knots). Hurricane is used in the North Atlantic Ocean, the Northeast Pacific Ocean east of the dateline, or the South Pacific Ocean east of 160E. Typhoon is used in the Northwest Pacific Ocean west of the dateline.
For many parts of the world a non-severe tropical cyclone is referred to as a tropical storm and assigned a name.
