Weather Facts


This is a collection of various weather facts we have collected through various sources, including our own Weather Dude. They help explain the why's and how's of the subject of meteorology, and we hope to answer any question that you might have about it. We also want to enhance your interest in this very complex subject. Remember, weather affects almost every aspect of your life in some way.
If you have a weather fact you'd like to share send it to: Dave

Are there any benefits from tropical cyclones?

Tropical cyclones do have some major benefits. Although these storms cause major damage on occasion and cause injury and death, they are really a necessary evil.

Dave


Can Contrails from Jetliners Indicate a Change in the Weather?

Contrails can actually indicate that a change in the weather is on its way, especially during the cooler months of the year.

Dave


Did You Know that Cold Air is heavier than Warm Air?

Cold air is much heavier than warm air and this is the basis for much of what we call weather.

Dave


Does hail always come before the tornado? Rain? Lightning? Utter silence?

Not necessarily, for any of those. Rain, wind, lightning, and hail characteristics vary from storm to storm, from one hour to the next, and even with the direction the storm is moving with respect to the observer.

NOAA


How are tropical cyclones different from tornadoes?

While both tropical cyclones and tornadoes are atmospheric vortices, they have little in common.

NOAA


How do tornadoes dissipate?

The details are still debated by tornado scientists. We do know tornadoes need a source of instability (heat, moisture, etc.

NOAA


How do you know when itís going to rain?

There must have been times when you see a big dark cloud move overhead and you say to yourself ìItís going to pourîÖ and nothing happens.

Dave


How Does Hail Form

Inside of a thunderstorm are strong updrafts of warm air and downdrafts of cold air.

National Weather Service


How large can hail get?

Fortunately...most hail is small - usually less than 2 inches in diameter

The largest hailstone ever recorded was in Aurora Nebraska on June 22nd 2003, the hailstone was recorded at 7 inches in diameter, and a 18.

NOAA


How many tornadoes hit the US yearly?

About one thousand. The actual average is unknown, because tornado spotting and reporting methods have changed so much in the last several decades that the officially recorded tornado climatologies are believed to be incomplete.

NOAA


Is there such a thing as Heat Lightning?

No, there is no such thing as heat lightning. What many folks call heat lightning is simply lightning from a very distant thunderstorm illuminating and reflecting off of the dust particles in the atmosphere over the observer.

Dave


Lightning - Things you may not know about this deadly and damaging phenomenon

Many people do not realize how truly dangerous lightning is and how mysterious this weather phenomenon can be.

Dave


Predicting Snow in the Hampton Roads Area... Why is it so challenging?

It is never easy for meteorologists in our area when the rain/snow line is going to be close by.

Dave


Should I tape my windows when a hurricane threatens?

No, it is a waste of effort, time, and tape. It offers little strength to the glass and NO protection against flying debris.

NOAA


Summer and Winter Precipitation Amounts - A Comparison of the West and East Coasts of the United States

Believe it or not, the summer is our wettest season here in the Hampton Roads area.

Dave


The Backdoor Cold Front

During the spring and summer months, you may hear the term backdoor cold front used by meteorologists in our area.

Dave


The Difference Between Hail, Sleet, and Freezing Rain

Many times I hear people say during a winter storm that it is hailing. This is actually called sleet.

Dave


The Difference Between Meteorological Winter and Astronomical Winter

Meteorological winter is a three month period that runs from Dec 1st to the end of February.

Dave


The Weaker the Tropical Cyclone, the Further West the Storm May Go

Did you know that tropical cyclones that remain weak as they track westward have less of a chance to re-curve to the north? This is because the stronger the storm, the higher the cloud tops extend into the upper-atmosphere.

Dave


Warm Fronts and Cold Fronts - A Brief Explanation as to How Precipitation Varies with Each Type of Front

Warm Front - A warm air mass is overtaking a cold air mass. Since warm air is less dense than cold air, it rises above the retreating cold air.

Dave


Water Vapor, the Natural Greenhouse Gas

Water vapor is one of the most effective greenhouse gases in our atmosphere.

Dave


What causes a drought like the exceptional Southeastern Drought of 2007?

Droughts are not headline grabbers like tornadoes, blizzards, hurricanes, heat waves, etc.

Dave


What causes thunder? What causes thunder to rumble sometimes and why does it sound like a crack or bang at times?

Thunder is caused by the rapid heating (and then cooling) of the air from lightning.

Dave


What causes thunderstorms in the Hampton Roads area?

The average number of days with thunderstorms in Hampton Roads is about 40 days annually.

Dave


What Causes Wind?

Wind is caused by the difference in pressure from one point on the earth's surface to another.

Dave


What direction do tornadoes come from? Does the region of the US play a role?

Tornadoes can appear from any direction. Most move from southwest to northeast, or west to east.

NOAA


What does Bombogenesis mean?

If you live along the east coast of the United States, you may have heard a meteorologist say that a storm system or low pressure area is bombing out or that bombogenisis is about to occur.

Dave


What does the term Zonal Flow mean?

You may have heard meteorologists use the term “zonal flow”. What does that mean? It means that the wind flow in the upper atmosphere will be predominately from west to east across most of the United States with no real dips in the jet stream.

Dave


What Does Wind Direction Mean?

When meteorologists talk about wind direction, does it mean the direction the wind is blowing from or blowing to? The answer isÖWind direction is where the wind is coming from.

Dave


What is a Sea Breeze?

Have you ever been on the beach and all of a sudden the wind shifts from off of the water and the temperature drops quite drastically? This sudden shift in wind which can be quite refreshing during spells of hot weather is most likely the result of a sea breeze.

Dave


What is a "Cape Verde" hurricanes?

Cape Verde-type hurricanes are those Atlantic basin tropical cyclones that develop into tropical storms fairly close (<1000 km [600 mi] or so) of the Cape Verde Islands and then become hurricanes before reaching the Caribbean.

NOAA


What is a hurricane, typhoon, or tropical cyclone?

The terms "hurricane" and "typhoon" are regionally specific names for a strong "tropical cyclone".

NOAA


What is a Noreaster?

Noríeasters are low pressure areas (extra-tropical storms) that develop along the southeast coast and move northeastward along the coast bringing copious amounts of rain and/or snow to the eastern seaboard.

Dave


What is a Sub-Tropical Storm?

Sub-Tropical Storms are actually a fairly new designation of ocean storms that have some tropical characteristics, but are not truly tropical cyclones.

Dave


What is an Alberta Clipper?

What is an Alberta Clipper? It is a low pressure area that develops usually in the Alberta Province of Canada and it moves rapidly southeastward towards the east coast.

Dave


What is an Isobar?

An isobar is a line on a weather map that connects points of equal barometric pressure.

Dave


What is an Occluded Front?

An occluded front occurs when a cold front overtakes the warm front in a low pressure storm system or an extra-tropical storm.

Dave


What is the Bermuda High?

The Bermuda High is a high pressure area that is usually centered in the vicinity of Bermuda during the spring and summer.

Dave


What is the Dew Point and Why is it so Important?

You have probably heard meteorologists talk about the dew point and you wondered what impact that it has on the weather.

Dave


What is the difference between isolated and scattered showers?

Have you ever wondered what the difference between isolated and scattered showers or thunderstorms is? Well, the National Weather Service (NWS) breaks this down into very easy to understand terminology.


What is the F-scale?

Dr. T. Theodore Fujita developed a damage scale (Fujita 1971, Fujita and Pearson 1973) for winds, including tornadoes, which is supposed to relate the degree of damage to the intensity of the wind.


What is the highest-elevation tornado? Do they happen in the mountain West?

The highest elevation a tornado has ever occurred is unknown; but it is at least 10,000 feet above sea level.

NOAA


What is the jet stream?

The jet stream is a river of fast moving air high in the atmosphere. Itís normally near the boundary between the troposphere and the stratosphere (tropopause).

Dave


What is the Low Level Jet?

You may have heard or seen the term low level jet used in the forecast discussion.

Dave


What is the origin of the word "hurricane"

"HURRICANE derived from "Hurican", the Carib god of evil... alternative

NOAA and AMS


What is the Weather Like During the Month of April in Hampton Roads?

The weather during the month of April can be just as changeable as March, but the cold doesn’t last as long, nor is it as intense as it was in March.

Dave


What is the Weather like during the Month of August in Hampton Roads?

The month of August is a very warm and humid month in Hampton Roads, with very few breaks from the humidity.

Dave


What is the Weather like during the Month of December in Hampton Roads?

Meteorological winter begins December 1st which basically means that, on average, December is the first of the three coldest months of the year.

Dave


What is the weather like during the month of February in Hampton Roads?

February can be a very volatile month as the normally active jet stream sometimes causes extremely cold Arctic air masses to plunge southward into the nation clashing with relatively warmer air masses that are pulled up from the south.

Dave


What is the weather like during the month of January in Hampton Roads?

January is the coldest month on average in Hampton Roads. It can be a very active month as the jet stream frequently brings low pressure systems across the Mid-Atlantic States.

Dave


What is the Weather like during the Month of July in Hampton Roads?

July is the warmest month of the year and believe it or not, it is on average, the wettest month of the year.

Dave


What is the Weather Like During the Month of June in Hampton Roads?

June begins the three month period known as “Meteorological Summer” which ends on August 31st.

Dave


What is the Weather Like During the Month of March in Hampton Roads?

The weather during the month of March is usually very changeable with wide swings in temperature.

Dave


What is the Weather Like During the Month of May in Hampton Roads?

The weather in the month of May in Hampton Roads varies from year to year as with any other month.

Dave


What is the Weather like during the Month of November in Hampton Roads?

November can be a very active month as the difference in air masses becomes greater as the month progresses.

Dave


What is the Weather Like During the month of October in Hampton Roads?

October is a transitional month as it begins with an almost summer-like feel to the air.

Dave


What is the Weather Like During the month of September in Hampton Roads?

September is a transitional month. The days are rapidly growing shorter and the sun’s intensity is weakening.

Dave


What is the Wettest Month of the Year on Average in Norfolk, Virginia?

Many people might be surprised that the wettest month of the year in Norfolk, Virginia is July, with August being a close second place.

Dave


What is Virga?

Virga is precipitation that evaporates before it hits the surface of the earth.

Dave


What single month had the most tornadoes?

The record for most tornadoes in any month (since modern tornado record keeping began in 1950) was set in May 2003, with 543 tornadoes confirmed in the final numbers.

NOAA


What was the biggest known tornado?

The Hallam, Nebraska F4 tornado of 22 May 2004 is the newest record-holder for peak width, at nearly two and a half miles, as surveyed by Brian Smith of NWS Omaha.

NOAA


What was the only Tropical Storm that had its name retired?

It was Tropical Storm Allison that flooded the Houston, TX area in June of 2001.

Dave


What were the deadliest U.S. tornadoes?

The "Tri-state" tornado of 18 March 1925 killed 695 people as it raced along at 60-73 mph in a 219 mile long track across parts of Missouri, Illinois and Indiana, producing F5 damage.


When does the Cape Verde season begin?

The Cape Verde season, which is when tropical cyclones form in the Eastern Atlantic, begins around the 15th of August.

Dave


When is it Warmer Near the Water?

On many days during the spring and summer months, you hear meteorologists say that the air temperatures will be cooler near the water.

Dave


When is the Peak of Hurricane Season in the Atlantic?

Based on averages since records have been kept on hurricanes, the peak of hurricane season is September 10th.

Dave


Where Cold Fronts Come to Die

During the summer months, cold fronts usually have trouble moving through our part of the world and many times they stall and dissipate over our region or just south and east of here over the coastal Carolinas.

Dave


Which tropical cyclone intensified the fastest?

Typhoon Forrest in September 1983 in the Northwest Pacific Ocean deepened by 100 mb (976 to 876 mb) in just under 24 hr (Roger Edson, personal communication).

NOAA


Why are nights with a clear sky sometimes colder than nights that are cloudy?

Clouds act like a blanket and actually prevent the heat gained from the previous day from escaping out to space.

Dave


Why are tropical cyclones named?

Tropical cyclones are named to provide ease of communication between forecasters and the general public regarding forecasts, watches, and warnings.

NOAA


Why do hurricanes hit the East coast of the U.S., but never the West coast?

Hurricanes form both in the Atlantic basin (i.e. the Atlantic Ocean, Gulf of Mexico and Caribbean Sea) to the east of the continental U.

NOAA


Why does a heat wave sometimes follow a cool spell in the spring and early summer?

While strange but true, many a heat wave has come on the heels of a cool spell in the Mid-Atlantic Region.

Dave


Why does autumn have more foggy mornings in inland areas than any other season of the year?

The main reason is the increasing length of darkness. This increases the time of radiational cooling thus causing the temperature to fall below the dew point.

Dave


Why Does the Size of Snowflakes Vary?

Did you ever wonder why snowflakes can be large and featherlike or very small? The reasons for the variability are complex but I’ll try to give you the basic reasons.

Dave


Why is August the most humid month of the year in Hampton Roads?

Did you ever wonder why the humidity levels in August are so high? The reason is that the ocean temperature reaches its peak in August, which is usually around the 80 degree mark off of Virginia Beach.

Dave


Why is fog more common during the fall?

Foggy mornings are much more common as we head into the autumn months and the reasons are quite simple.

Dave


Why is it Hotter During a Drought?

Did you know that the dryness actually helps to add to the higher temperatures during a drought? How? In normal conditions, some of the energy from the sun is used up to evaporate moisture in the ground, vegetation and other various surfaces.

Dave


Why is March such a windy month?

You may wonder why March is such a windy month compared to the other months of the year.

Dave


Why is there sometimes no frost on cold mornings?

Wind speed plays a major role in frost development. When the winds are calm (or very light) and temperatures are cold enough, frost is likely.

Dave


Why the mornings are normally less windy than the afternoons?

The reason is this. During the afternoon, the sun's heating is the strongest and this heating destabilizes the atmosphere.

Dave


Why the United States Ranks Number One in Tornado Frequency in the World

There is no other country in the world that has more tornadoes per year than in the United States of America.

Dave