Weather and Climate

This page contains the text from the handout for the Forecasting the Weather Class that I teach. The pictures from the slides shown during the class follow the text. Reference material that was used in preparing the text for the class appears near the bottom of the class text under tools and on-line references.
The area around Greene, NY was hit by 2 floods in 2006 (6/28-29/2006 and 11/29/2006). This was the initial drive to give a discussion on weather that was open to the local community in order to raise awareness of weather and flooding. The weather class resulted from this initial idea.

The windvane above is mounted outside the house on a long pole. I made it a few years ago, for more information on the metalworking see the Metal Working Page on this site.
Another weather related project of interest is the ULF/VLF receiver that can detect lightning at great distances. Information on it can be found on the RF Electronics Projects Page.

This picture is of the sky when a very strong cold front passed through near home one afternoon this summer. The boundary between the weather system was quite dramatic and clearly visible in the sky. The temperature dropped about 20 degrees F in 30 minutes with the passage of the front.

I have also been working on some temperature data logging. It has enabled me to track the outdoor temperature for days at a time. It has allowed a close look over time of some sharp cold fronts that have passed through the area. More information on data logging can be found on this site at the Temperature Data Logging page.

Further Reading
The following link is to the National Weather Service Jetstream Online School for Weather. It is worth looking at to learn more about weather. It is laid out in topics that can be studied one at a time. Each topic can be considered to be a short class that can stand by itself and can be covered in the same time period as a single class would normally take.

NWS JetStream - An Online School for Weather

See the links page on this website as well.

Weather Pictures for Class

Weather/Climate Data for Class

Introduction- Weather can be predicted to a degree by simple observation of the sky. This can be enhanced by keeping track of the barometric pressure. With a little effort in noticing what is going on in the sky and observing the trends, good predictions can be made. Comparing guesses against what is reported by the weather services is a way to help refine predictions. Knowledge of the climate itself, in general and the local effects helps to connect a person with the cycles of the earth and how they are coupled with the weather.

In the end all weather is caused by the sun ( also much of the energy we use came from the sun, think about it). Weather is modified by the earth's rotation, land masses, mountains, ocean current and ground temperatures.

Global air circulation- The basic idea is that warm air rises and cold air falls. One would expect that the warm air from the tropics would rise there and move northward to fall back down at the poles. And the cold air at low altitudes would go back toward the equator. This is the simple one cell (Hadley Cell) model.
In reality the warm air only makes it part of the way up from the equator (~ 30 degrees lat.) before falling, the Hadley Cell. From the poles to 60 degrees latitude there is a circulation cell where cold air circulates from the poles to 60 degrees rises and move back towards the poles, the Polar Cell. Between these is another circulation cell from 30-60 degrees between the others (Ferrel cell), with air moving down at 30 and up at 60. This splits the northern hemisphere into three circulation cells, aligned roughly with the boundaries of the arctic, temperate and torrid regions.
Simplistically, air rises near the equator( Low Pressure) sinks near 30 degrees (High Pressure). Rises near 60 degrees (High Pressure). Around the equator, plus or minus a few degrees depending on summer and winter, the region of semipermanent low pressure band that encircles the Earth. Thunderstorms and heavy rains occur within this band. This moisture is responsible for the rain forests and jungles of the equatorial region.
Around 20-30 degrees North and South latitude there are regions of semipermanent high pressure that is responsible for most of the deserts of the world.


Summary of air circulation at ground level

Latitude Deg. N    Behavior          Pressure        Comment

90(North Pole)     Divergant-Sinking     H           Cold and dry.
60                 Convergant-Rising     L           Location of Polar Cold Front - Polar Jet Stream rides here at high altitude.
30                 Divergant-Sinking     H           Deserts located 20-30 Degrees - Main Jet Stream rdies here at high altitude.
0                  Convergant-Rising     L           Stormy region, thunderstorms, tropical rain forests.

The fact that the earth is spinning adds yet another modification to this. The spinning earth twists the movement of air from a north-south circulation to a prevailing movement of easterlies and westerlies. For our temperate region a general westerly flow prevails, for the Polar Regions it is easterly. At the regions were the flow is up or down, the equator and the so-called horse latitudes the air is quite free from a prevailing flow. The latitudes between the so called horse latitudes (~30 degrees) and the equator are referred to as the trade winds, because of there prevailing easterly flow.
The twisting effect on the winds is called the Coriolis effect. A wind that would be expected to move from High to Low pressure in the Northern hemisphere is twisted to the right. The higher the speed of an object( air as wind in this case) and the closer to the poles, the stronger the effect.
Fact: On a weather map the winds follow the lines of equal pressure (isobars) at high altitudes. The closer the isobars are to each other the stronger the winds.

The earths spin also modifies the local wind direction around high and low pressure systems. This is caused once again, by the Coriolis Effect. It causes wind at high altitude to circulate clockwise around high pressure systems and counterclockwise around low pressure systems. Near the ground wind direction is modified slightly by the drag caused by the Earth's surface and other objects. It is modified in such a way that wind points slightly away from the high pressure center and slightly towards the low pressure center.
I will leave it at that, to go any further on this topic would require vector math.


Summary of winds in the North Hemisphere 

Latitude Deg. N    Prevailing Behavior                 Comment

60 - 90            Polar Easteries 
30 - 60            Temperate Westerlies
~30                None                                Calm - Horse Latitudes - Why the name?
0 - 30             Tropical Easterlies                 Trade winds
~0                 None                                The Doldrums

Pressure Trends and Weather

High Pressure - Typically cooler, dryer, fair skies. Winds rotate clockwise around high pressure centers. Wind speed depends on how 'steep' the slope is between high and low. The air is sinking within areas of high pressure; causing it to be denser.

Approaching High - Bad weather breaking up. Pressure rising, winds shift to the North or Northwest. Cooler/ Drier.

Arrived High - Clear skies, possible fair weather puffy clouds. Low Humidity, calm winds. West if the High is to the south, east if to the north. Stable temperatures, cool nights, clear. Pressure High and stable. Contrails dissipate quickly during the day. Crisp stars and moon.

Leaving High - Warmer, winds shifting the South or Southeast. Warmest temperatures. High thin clouds make an appearance, contrails stay in the sky. Moon appears surrounded by a ring or blurry.

Low Pressure - Warmer, wetter. The air is generally rising within areas of low pressure. Winds rotate counterclockwise around low pressure centers. Wind speeds once again depend on steepness of pressure difference between high and low. Low pressure areas form between areas of high pressure and tend to form along weather fronts. Sometimes several of them will be located along a front that covers a large distance.

Approaching Low- Warmer, winds any where from NE to S, typically S or SE. Increasing is speed for a while then settling down. High clouds thickening, ground glass sky. Finally lowering and thickening to obscure sky.

Arrived Low- Calmer winds, rain starts lightly at first then steady.

Leaving Low- Spotty precipitation winds shift to the North or Northwest. Cooler/ Drier. Going back into approaching high.

The cycle of High to Low and back is approximately 5-7 days. This roughly coincides but is not related to the moons phases.

Fronts

Fronts form along boundaries between weather systems of different temperature and humidity. Fronts separate two different types of weather.

The winds are generally going in different directions on each side of a frontal boundary. The following is a basic rundown of the most common fronts that occur in our area.

Cold Front - Cold air displaces warm by wedging underneath. This forces air higher and higher generating tall clouds associated with thunderstorms and snow squalls in the winter. The higher the altitude, the cooler the air is. More and more moisture that is present in the air condenses at high altitudes. Water and ice particles eventually can reach a size that will fall as precipitation.

In a thunderstorm a chimney effect causes more and more warm air to rise quickly, condensing rapidly, resulting in heavy precipitation. The cold front passage is marked with a line of energetic weather and gusty winds that shift direction as the front passes. In the more energetic systems hail can form as the back edge of the thunderstorm passes through a region. The temperature will also drop rapidly. Gusting winds will occur and change direction as the front passes.

Warm Front - It is more difficult for warm air to displace cold. It tends to ride up over the cooler air and it displaces it gradually over a period of days. The progressions of clouds signaling an approaching warm front are as follows. High thin stratus (layer) to thicker and lowering stratus from which precipitation finally falls. The initial approach of the warm front can be detected by observation of clouds. First high thin clouds and/or high herringbone (cumulo-stratus) clouds will appear, contrails will begin to stay in the sky. This is a sign of upper level moisture in the atmosphere. The clouds that follow will lower and thicken as the warm air displaces the cold air. The temperature will rise slowly and when the clouds cover the sky fully (nimbostratus) precipitation will fall.

Weak Fronts - A weak cold front may pass causing a slight drop in temperature, with some wind and clouds that move fast through the sky. This would normally end in clearing skies. Typically associated with high clouds. Very high clouds that are high enough exhibit curvature.

A weak warm front may produce days of cloudiness with no rain.

Stationary - Produces the same weather, good or bad for an extended period of time, sometimes days. The fronts stay put, therefore the weather stays the same.

Occluded - Cold fronts generally move faster than warm fronts. Therefore they can overrun a warm front. The cold front can drive itself under a warm front wedging it aloft. This forms a triple point where both fronts converge. Occluded fronts can occur in the vicinity of mature low pressure systems.

Climatology

Sun angle and its effects - The position of the sun moves from the equator at the vernal equinox to 23.5 degrees North on the summer solstice back to the equator on the autumnal equinox, to 23.5 degrees South on the Winter solstice.

The noon peak sun angle in degrees is related as follows, assuming we are at 42 degrees North is as follows. Equinoxes, 90 - 42 = 48, Summer solstice 48 + 23.5 = 71.5 Winter Solstice 48 - 23.5 = 24.5. This coupled with the length of day at 9:05 hrs Winter Solstice, 12:11 at the Equinoxes, 15:15 at the Summer Solstice, gives the amount of solar energy reach the face of the earth.

The sun angle and length of day combine to influence heating of the earth, ocean and atmosphere. This heat is uneven from place to place and tends to make the air want to move around the earth as discussed earlier with reference to global air circulation.

Many times when the sun goes down the winds calm as the air is no longer driven by convective heating. At night the cool air tends to fall and will travel downhill, in the morning this trend reverses.

Inertia - Average temperatures lag the seasons by about 36 days. The lowest average temperature for the winter season here will occur Jan 27, 2007. The maximum average summer temperature will occur July 27, 2007. The maximum rate of change up will be Apr 25 and down will be Oct 29 respective to the equinoxes. This lag is due to the fact that the ground and water bodies retain heat and that the atmosphere being a giant ocean of air cannot respond immediately to changes either. On a daily basis there is a lag also, it warmer somewhat later in the afternoon rather than at noon when the solar radiation reach the earth is the most powerful. This lag is present in most large scale natural systems.

Average Temperatures (Deg F.) for Greene, NY (estimated projection) from a computer program that I wrote.(L = Low, H = High, A = Avg.)


         L   H    A
1/27 -   5   23   14
4/25 -  33   51   42
7/27 -  62   80   71
10/29 - 32   50   41

Seasons - The length of the seasons are not equal, 3/20-6/21 = 93 days, 6/21-9/23 = 94 days, 9/23 - 12/22 = 90 days, 12/22 - 3/20 = 89 days. This is due to the sun being further away in winter, peaking in distance at about January 5th. It takes it longer to cover the same distance in space over the winter, lengthening winter with respect to summer.

Using a computer program to obtain the rise and set time for Binghamton NY and Asheville NC, I derived the following chart. It compares the two locations and shows the difference in sun rise/set and length of day between them.

Asheville (82.57 deg W) lies West of Binghamton (75.75 deg W) So the day is shifted to favor the sun rising and setting later by an average 33 minutes. Clearly the greatest difference is near the Winter solstice where it sets almost an hour later. The length of day is not as short in Asheville as it is in Binghamton at the Winter solstice. Good news for solar heating and Seasonal Affective Disorder sufferers!

At the equinoxes, only Spring is shown, Fall would be identical, the length of day for both is nearly equal.

The data shows that at the Summer solstice there is little difference as well. In my mind I would have expected more spread in the rise/set times and length of day between the two cities in the summer as well, with Binghamton winning the day length competition. But the data reveals otherwise.


Sun Rise/Set, Length of Day Comparison.
Binghamton NY -v- Asheville NC Times in EST
Differences (Asheville - Binghamton) in minutes


Date         Location       Rise    Set    Length
3/20/2007    Binghamton    06:02   18:08   12:06
             Asheville     06:34   18:42   12:08

             Diff.(A-B)       32      34       2

6/21/2007    Binghamton    04:21   19:36   15:15
             Asheville     04:54   20:11   15:17
             Diff.(A-B)       33      35       2

12/22/2007   Binghamton    07:22   16:29   09:07
             Asheville     07:36   17:21   09:45
             Diff.(A-B)       14      52      38

What matters for climate as well as the length of day is the solar angle which connects to the actual amount of solar radiation energy that reaches the surface of the earth and the atmosphere as discussed above.

Climate Regions on the East Coast - The northeast is a humid continental region, south of NJ and PA the region transitions into humid subtropical. The Appalachian Mountains are high enough to still be a transition region all the way to Georgia. The rest of the central Atlantic and southern states are humid subtropical. The very southern tip of Florida including the keys and the eastern gulf coast of Texas are the only 2 places that are considered tropical in the continental US. The Florida Keys are in fact considered free from the possibility of frost. Climate data is used to determine when the first and last days of frost will occur. From this various zones 1-9 are determined for agricultural purposes.

Temperate climates extend from the tropics of Cancer and Capricorn, north or south to the arctic circles experience the four seasons. Tropical regions experience a cooler dry "winter" and a warm hot wet "summer". Some tropical regions can have three levels, cool, hot, followed by wet.

Odd/Local Weather

Lake effects - After bad weather clears out in the winter, winds shift to the W/NW. The Great Lakes being warmer than the land and large bodies of water liberate significant moisture into the air. This condenses causing trails of clouds, think of smokestacks. The cloud trails cross this region, snow eventually falls from them as they cool and are driven over elevated land. As a typical one-two punch in the winter for our area is that, we get snow and just as it clears out, lake effect snow starts up for a period of days. Lake effect typically happens early in the winter before the lakes are not frozen. It also contributes to winter cloudiness. If the lakes were not there we would more clear days and less snow in the winter. Lake effect can cause confusion in weather prediction. The confusion is that the barometer is rising (fair weather) but it is cloudy, blowy and snowing.

Perpetual Cloudiness - This area has the 2nd lowest rate of insolation (amount of solar radiation reaching the earths surface), bad for solar heating! The average amount of sun per day is 3.16 for Binghamton; Chicago is 3.14 out of 102 cities. Most of the cloudiness is in the winter. Climate data from...

http://www1.ncdc.noaa.gov/pub/data/ccd-data/

... which shows this off clearly. It has to do part with the prevailing westerly flow of air across the lakes and the basin formed over the Binghamton area by the confluence of the river valleys (Chenango, Susquehanna). The high hills to the east of Binghamton allow the clouds to pile up, not a scientific term. From commuting into the region from the east over several years it is apparent when one crosses the divide between the Delaware and Susquehanna river basins, the ridge has more 'weather' on this side. On Rt. 17 this point is just before going downhill into Windsor.

Many times during the spring and fall it is possible to go a short distance away from Binghamton and drive into less cloudy weather. Ithaca in particular is a good spot to go to. The Finger Lakes tend to moderate the weather nearby and actually keep the cloud level down. It can be observed in the satellite and radar images on-line that there sometimes is a 'blob' of clouds parked over the Binghamton region in fall and winter and nowhere else in the area is there cloudiness.

42nd Parallel - Folklore has is that the 42nd parallel separates different kinds of weather in our region. This is the line between PA and NY nearby us. This roughly correlates with the aforementioned perpetual cloudiness, lake effect possibly also starting the trail off at this distance. Another factor is the river changing direction at Great Bend, PA which coincides with the border. The mountain range changes direction as well so that when you cross into PA soon you will leave the region of micro climate that is over Binghamton.

Jet Stream- There are actually two jet streams that form at very high altitudes. One of them,the Polar Jet Stream,rides along the boundary between the Polar Cell and the Ferrel Cell. The Polar cold front would lie below and to the South of it.
The temperate jet stream lies near the boundary of the Ferrel Cell and the Hadley Cell, it is once again at a high altitude.
The jet streams are a river of high speed air that encircles the globe with the air flowing from west to east. They can affect the temperature latitudes that we live in. When the Polar jet stream drops to the South during the winter, we will get cold air over our region. The converse is true as well, sometimes the loop can go up above us and stay there. This can allow it to be mild for extended periods of time. The effect of the Polar jet stream is more pronounced during the Winter months when it is strongest. The temperate jet stream is weaker than the Polar jet stream and has less to do with the weather of our region.

I have read somewhere( I can't remember where ) that the jet stream certain amount of loops in it; they have to be a whole number. Sometimes it will snap to a different number, repositioning where the loop lands in the continental US. This can lead to different weather patterns. I have noticed that sometimes weather changes will happen mid-season, so that you may get a hot/dry start of summer followed by cooler/wet or the other way around. This can happen in winter as well. I have not paid a lot of attention to what the jet stream was doing at those times. It is something I will have to look for in the future.

The following link shows graphical representations of the jet stream, both current and forecast winds. The graphs are shaded to show wind speeds above 60KMH. There are also graphs of the jet stream winds superimposed on satelite images.
CRWS Jet Stream Map Menu

I have observed a pattern.There is a distinct 2 year pattern; generally bad winters come 2 in a row. This might be related to the jet stream or El Nino/La Nina. Certain winter/summer patterns can couple in this way as well, extreme winter/summer, 2nd half of summer extreme, 1st half of winter extreme or just the opposite. I would like to know more about this myself, I am as always open to ideas.

Noreaster - A coastal storm where the low pressure is off of the east coast of the US. The wind traveling counterclockwise around it pulls in moisture from the Atlantic Ocean and deposits it over land. The winds are from the northeast meaning that the low pressure center is east of us and to the north bringing in cold moisture that can result in a lot of snow in the winter.

Floods - Floods are the biggest natural disaster threat in our area. Most deaths occur from floods in this area than from any other natural disaster. Floods can occur at any elevation when a quick heavy storm occurs. Culverts overflow and cause water to take paths that it normally would not. Flooding is compounded in poor drainage areas and when the ground is saturated.

Main stem and river flooding typically involves low lying flood plains. Rain over many days, snow melt and a saturated ground all set up the potential for this type of flooding.

Things to look for

If contrails stay in the sky there is upper level moisture forming. Precipitation will generally be arriving in 2-3 days. This will sometimes be followed by herringbone clouds and a ground glass look to the sun or moon which is further evidence of bad weather approaching.

If smoke from chimneys stays low and birds fly low, precipitation is approaching soon.

Winds from North to Southwest mean fair weather, South to Northeast fowl weather.

A clear night and fog in the morning generally mean a rain free day.

The air in front of a thunderstorm or an isolated heavy rain cloud is generally sinking and calm, when it starts to gust there is only a minute or two to take cover.

Tools

Temp/Hum/Barometer - Many models are available relatively inexpensively today. Digital ones are available from many sources for under $100. Local sources include Radio Shack, Gander Mountain and Sam's Club.

http://www.hometrainingtools.com/catalog/earth-space-science/weather-climate/p_as-digwbht.html- $40

Cloud Identification and Weather Book

http://www.hometrainingtools.com/catalog/earth-space-science/weather-climate/p_bk-weatwiz.html- $9

Cloud Chart 17 inches X 22 inches

http://www.hometrainingtools.com/catalog/earth-space-science/weather-climate/p_as-cloud.html- $4

Weather Radio & Warnings - Inexpensive ones can be bought that have programmable alerts. These alerts only sound when threatening weather is moving into your county. Some are built to trigger different levels of alert depending on the severity of the approaching weather.

Watch - Conditions are favorable for ________.

Warning - _______ is occurring, imminent or highly likely.

Advisory - Hazardous weather conditions are occurring, imminent or likely. Conditions will cause a significant inconvenience and if caution is not exercised...(Advisory is not as urgent as a warning.)

Online References

Short term map forecast for 0000 and 1200 UTC, 8AM and 8PM EDT.

http://www.hpc.ncep.noaa.gov/basicwx/92f.gif

Shows High & Low Pressures, precipitation, fronts and pressure isobars for continental US.

Good to use to compare reading the clouds against what is happening on the weather map.

Text based forecast for our zone.

http://weather.noaa.gov/cgi-bin/iwszone?Sites=:nyz045

Contains...

Zone Forecast for Chenango, NY, 7 days text based.

State Forecast for New York7 days tabular statewide forecast.

Area Conditions for Chenango, NY

Nearby Cities- Sky, weather conditions, temp, dew point, relative humidity, wind speed and direction, barometric pressure and remarks.

Climate data from the entire US.

One file is a PDF the others are the same data broken down by category in a text file format. The text files are suitable for import into spreadsheets.

http://www1.ncdc.noaa.gov/pub/data/ccd-data/

Quick one page summaries with bar graphs for many cities.

http://www.cityrating.com/weatherhistory.asp

Climate

Some further climate information, details these climates around the world.

http://en.wikipedia.org/wiki/Continental_climate

http://en.wikipedia.org/wiki/Humid_continental_climate

http://en.wikipedia.org/wiki/Temperate

Fronts

This one has all of the symbols for the fronts.

http://en.wikipedia.org/wiki/Weather_front

Satellite and Radar images of the US.

http://www.weather.gov/sat_tab.php?image=ir

Severe Weather: Warning, Watches and Advisories Defined

http://en.wikipedia.org/wiki/Severe_weather_terminology_%28United_States%29

Hazardous weather risks: repeated here

The various weather conditions described above have different levels of risk. The NWS uses a multi-tier system of weather statements to notify the public of threatening weather conditions. These statements are used in conjunction with specific weather phenomena to convey different levels of risk. In order of increasing risk, these statements are:

Outlook - A hazardous weather outlook is issued daily to indicate that a hazardous weather or hydrologic event may occur in the next several days. The outlook will include information about potential severe thunderstorms , heavy rain or flooding, winter weather, extremes of heat or cold, etc., that may develop over the next 7 days with an emphasis on the first 24 hours of the forecast. It is intended to provide information to those who need considerable lead time to prepare for the event.

Advisory - An advisory is issued when a hazardous weather or hydrologic event is occurring, imminent or likely. Advisories are for less serious conditions than warnings, that cause significant inconvenience and if caution is not exercised, could lead to situations that may threaten life or property. NWS may activate weather spotters in areas effected by advisories to help them better track and analyze the event.

Watch - A watch is used when the risk of a hazardous weather or hydrologic event has increased significantly, but its occurrence, location or timing is still uncertain. It is intended to provide enough lead time so those who need to set their plans in motion can do so. A watch means that hazardous weather is possible. People should have a plan of action in case a storm threatens and they should listen for later information and possible warnings especially when planning travel or outdoor activities. NWS may activate weather spotters in areas affected by watches to help them better track and analyze the event.

Warning - A warning is issued when a hazardous weather or hydrologic event is occurring, imminent or likely. A warning means weather conditions pose a threat to life or property. People in the path of the storm need to take protective action. NWS may activate weather spotters in areas effected by warnings to help them better track and analyze the event.