Meteorology 101 & 201

This will be a page deicaded  to weather basics. what do i mean when i say gfs or talk about lapse rates. kids and everyone else this will be a great way to learn weather. welcome to meteorology 101.  our first term is meteorology which means  the study of the weather and atmosphere.

2. weather models are often used in forecasting weather several will be discussed often on the blog. they include the GFS ( 1-16 day range) 4 updates daily NAM (1-5) day range 4 updates daily Euro (1-10 day range) CMC ( Canadian) (1-10 day range) JMA ( Japanese) (1-10 day range) NGM (48hrs) UKMET( England) 1-5 day range NOGAPS( US NAVY)1-8 day. All of those not listed as updated 4 times daily are updated twice a day.

3. model bias. Each model is a different projection of how the weather pattern may evolve over the next several days and each model has bias when dealing with certain weather patterns. These biases will be discussed in the posts as situations present themselves.

4. how to read the models and the upper levels of the atmosphere will be explained as situations occur, each event and season is different.

different pressure level maps are used to show different meteorological condtions

850 mb- temps, pressure patterns

700 mb- moisture

500 mb-vorticity, geopotential heights  

300 mb- jet energy

5. precip types and atmospheric conditions to produce them

rain- all levels above 32*

snow- all levels below 32*

sleet- thin layer of above 32* air in the atmosphere causing snow to melt but then has time to refreeze.

Freezing rain- atmosphere is above 32* except at the surface rain falls and freezes on contact,

6. verga, humidity and dewpoint- humidity is a ratio between the temperature and the amount of moisture in the air, dewpoint measures the amount of moisture in the air. Verga is when radar detects precip in the base of the clouds which evaporates before hitting the ground.

7. types of fronts, clouds and airmasses- there three types of fronts warm, cold and occluded. A warm front separates a cold air mass from one that is warmer on the other side of the front overrunning of warm air into a colder air mass can often produce light precip. A cold front brings on colder air to replace the warmer air that was present these often feature more violent storms than warm fronts. An occluded front is one that is trapped between two strong and differing air masses, these fronts are often stalled or slowly move any direction over the course of several days bringing drastically different weather patterns from day to day. There several types of clouds, thick gray blanket clouds are stratus puffy clouds in the midlevels are cumulus and thin high level clouds are cirrus. Thunderstorm clouds go high up into the sky through all levels and are often gray with and anvil shape. Types of airmasses are Continental which are dryer and maritime which are wetter, these can put into several categories polar, Arctic and Pacific. Continental arctic air for example is cold and dry.

8. lapse rates and instability- The degree of stability can differ each day high pressure usually results in sinking air which leads to stability. Low pressure can lead to instability and rising air as air rises it cools and condenses producing cloud cover and precipitation. The measurement of instability is known as a lapse rate the avg is 6.4*C/1000M.  CAPE- convective alvaibale potential energy is amesure of instabilty, higher than value more instabilty CIN- convective inhibition is the reverse of CAPE. LI (lifted index)  is another indicator of instabilty lower the number the higher the instabilty.  

9. what makes a storm severe- the NWS has criteria for this the storm must have wind gusts over 58mph, produce 1  inch hail or a tornado. Lightning or flooding does not make a storm severe. The enhanced fujita scale categorizes tornadoes from 0-5 based on wind strength. for more info check www.crh.noaa.gov/lmk for the storm spotter book.

10. Hurricanes start as waves which form off the west coast of Africa which then strengthen due to warm water and low wind conditions. once the wind speed reaches 39 Mph it is a tropical storm 74 mph a cat 1 hurricane the safer Simpson scale goes from cat 1-5 based on severity.

11. isentropic lift- advection of higher mositure and pressure advections involves warm air overunning cold air. common in winter storms.