Property of Lear Siegler

FRONTAL WEATHER Property of Lear Siegler

Terminal Learning Objective Page D-1 in Student Handout: ACTION: CONDITION: STANDARD:

Identify the characteristics common ELO Identify the characteristics common to all fronts IAW FM 1-230.

OF DIFFERENT DENSITIES. WARM COLD A FRONT IS A BOUNDARY BETWEEN AIR MASSES OF DIFFERENT DENSITIES. Property of Lear Siegler

WARM COLD Frontal formation: When two high pressure cells exist so that the circulation of air is converging between them, a front is formed. The converging air currents veer upward creating a zone (trough) of low pressure. Property of Lear Siegler

cP H L mT Property of Lear Siegler

A TEMPERATURE INVERSION Frontal weather is caused by the lifting of warm moist air by colder more dense air. ALL FRONTS HAVE A TEMPERATURE INVERSION

FRONTAL DISCONTINUITIES TEMPERATURE DEWPOINT PRESSURE “ FALL THEN RISE” WIND SHIFT : APPROX 90° DRIFT CORRECTION TO THE RIGHT Property of Lear Siegler

Primary factors affecting frontal weather are slope, speed, moisture content, and stability.

questions ?

Identify the general characteristics ELO Identify the general characteristics of a cold front IAW FM 1-230.

Property of Lear Siegler

Cold Front The leading edge of a cold air mass, normally moving toward the southeast. Property of Lear Siegler

Warm Front Cold Front Property of Lear Siegler

Cold Front Slope Clouds Width of weather band Winds Direction of movement Speed Symbol

Cold Front Slope – avg. 1:80 1 mile 80 miles

Cold Front COLD AIR WARM AIR COLD FRONT 25,000’ 20,000’ 15,000’ CUMULONIMBUS 20,000’ cumuliform predominant 15,000’ 10,000’ COLD AIR WARM AIR Cold Front COLD FRONT Property of Lear Siegler

Post-frontal, can be violent type of weather Post-frontal, can be violent Cold Front Property of Lear Siegler

Width of weather band 50 miles Cold Front Property of Lear Siegler

northwest southwest Cold Front Winds

Property of Lear Siegler

1000 996 992 Property of Lear Siegler

southeast Direction of Movement

Average 25 knots Speed

If speed of front exceeds 25 kts a squall WARNING! If speed of front exceeds 25 kts a squall line may form as much as 300 miles ahead. Squall lines may include tornadoes, hail, and destructive winds! Speed

Property of Lear Siegler

Property of Lear Siegler

SQUALL LINE Property of Lear Siegler

color - blue triangle shapes, pointing in direction of movement Symbol NOTE: You must recognize in color and black and white. color - blue triangle shapes, pointing in direction of movement Symbol

questions ?

a. slope -1:80 b. cumuliform clouds c. 50 mile wide band of coverage d. winds NW behind front, SW ahead e. moves southeast f. 25 knots average speed Property of Lear Siegler

Property of Lear Siegler

Identify the general characteristics ELO Identify the general characteristics of a warm front IAW FM 1-230.

being overridden by warmer air. Warm Front The trailing edge of a cold air mass, normally moving generally toward the northeast, being overridden by warmer air. Property of Lear Siegler

being overridden by warmer air. Warm Front The trailing edge of a cold air mass, normally moving generally toward the northeast, being overridden by warmer air. Property of Lear Siegler

Warm Front Slope Clouds Width of weather band Winds Direction of movement Speed Symbol

Warm Front Slope – avg. 1:200 1 mile 200 miles

stratiform predominant Warm Front Property of Lear Siegler

b. Stratiform clouds predominate c. 400-600 mile band of coverage a. Slope - 1:200 b. Stratiform clouds predominate c. 400-600 mile band of coverage d. Wind SW behind, SE ahead of the front e. Moves Northeast f. 15kts avg speed Property of Lear Siegler

WARM AIR COLD AIR WARM FRONT Width of weather band MILES 25,000’ 20,000’ Width of weather band 15,000’ Ci 10,000’ Cs As WARM AIR Ns St COLD AIR 400 to 600 miles 100 200 300 400 500 MILES WARM FRONT Property of Lear Siegler

WARM FRONT Winds southeast southwest

Property of Lear Siegler

WARM FRONT northeast Direction of Movement

WARM FRONT Average 15 knots Speed

WARM FRONT color - red half moon shapes, pointing in direction NOTE: You must recognize in color and black and white. color - red half moon shapes, pointing in direction of movement Symbol

Unstable Warm Front Property of Lear Siegler

questions ?

ELO Identify the general characteristics of a stationary front IAW FM 1-230.

H H Stationary Front A front which is not moving, speed of zero to less than 5 knots. H H Property of Lear Siegler

Stationary Front Slope similar to Clouds warm front Width of weather band Winds Direction of movement Speed Symbol similar to warm front

Movement - unpredictable Stationary Front Winds – light and variable, tend to parallel isobars. Movement - unpredictable Speed – zero to < 5 kts H H Property of Lear Siegler

Stationary Front combination of symbols for cold and warm fronts, alternating sides of line of front NOTE: You must recognize in color and black and white. color – alternating red and blue Property of Lear Siegler

questions ?

Identify the general characteristics ELO Identify the general characteristics of an open wave IAW FM 1-230.

Open Wave L A wave-like appearance with one portion a cold front and the other a warm front with an open area in between. Property of Lear Siegler

Vertical cross section. Open Wave Warm Air Colder Cold Vertical cross section. Property of Lear Siegler

Stationary Front Mostly forms along a stationary front, but may form from any existing front. L Property of Lear Siegler

Open Wave L Property of Lear Siegler

L Cold Front Warm Front Property of Lear Siegler

Open Wave L Property of Lear Siegler

Open Wave L Property of Lear Siegler

Open Wave L Property of Lear Siegler

L Open Wave Weather Warm front WX Cold front WX Warm air Property of Lear Siegler

direction along the line of Open Wave L Movement Travels in easterly direction along the line of the original front Property of Lear Siegler

Weather chart portrayal Open Wave L Warm front Weather chart portrayal Cold front Property of Lear Siegler

A B Property of Lear Siegler

Property of Lear Siegler

questions ?

ELO Identify the general characteristics of an occluded front IAW FM 1-230.

Occluded Front: The result of a faster moving cold front overtaking a slower moving warm front. The effect is one front on top of the other squeezing warm air between.

Warm Air Colder Cold Open Wave Occluded Front: The result of a faster moving cold front overtaking a slower moving warm front. The effect is one front on top of the other squeezing warm air between. Property of Lear Siegler

Warm Air Colder Cold Open Wave 25 kts. 15 kts. Property of Lear Siegler

Open Wave Warm Air Colder Cold Property of Lear Siegler

Cold Occlusion Warm Air Colder Cold Property of Lear Siegler

Cold Occlusion Warm Air Colder Cold Property of Lear Siegler

Two types of occlusions: Cold front occlusion – The cold front runs underneath the warm front. (coldest air is behind the cold front) Warm front occlusion – The cold front overruns the warm front. (coldest air is ahead of the warm front)

Warm Air Colder Cold Open Wave Cold front occlusion – The cold front runs underneath the warm front. (coldest air is behind the cold front) Warm Air Colder Cold Property of Lear Siegler

Cold Occlusion Warm Air Colder Cold Property of Lear Siegler

Cold Occlusion Warm Air Colder Cold Property of Lear Siegler

Warm Air Cold Colder Open Wave Warm front occlusion – The cold front overruns the warm front. (coldest air is ahead of the warm front) Warm Air Cold Colder Property of Lear Siegler

Warm Occlusion Warm Air Cold Colder Property of Lear Siegler

Warm Occlusion Warm Air Cold Colder Property of Lear Siegler

Occlusions: cloud types Both warm and cold front types stratiform and cumuliform

Occlusions: weather Weather associated with each of these fronts combines widespread low ceilings and poor visibilities of the warm front with the severe weather of the cold front.

Occlusions: winds Ahead of the occlusion vary south to east generally from the southeast, behind the front generally from the northwest.

Similar to an open wave, to the east Occlusions: movement Similar to an open wave, to the east

direction along the line of Cold Occlusion Travels in easterly direction along the line of the original front Property of Lear Siegler

Portrayal: cold occlusion

Warm Occlusion Portrayal: warm occlusion Property of Lear Siegler

questions ?

ELO Identify the proper flight procedures to use when dealing with frontal weather IAW FM 1-230.

Each type front presents certain problems to the aviator. The aviator RECOGNITION OF TYPE: Each type front presents certain problems to the aviator. The aviator must learn to recognize type of front in order to apply proper procedures.

FLIGHT CONSIDERATIONS: Cold fronts and squall lines DON’T GO!

FLIGHT CONSIDERATIONS: Warm fronts Sufficient fuel for a long flight and possible diversion to an alternate airfield

FLIGHT CONSIDERATIONS: Stationary fronts Same as warm front, plus alert for open wave and occlusion

FLIGHT CONSIDERATIONS: Open wave Avoid the crest of the wave and cold front, cold front procedures for cold side, warm front procedures for warm side

WARNING! FLIGHT CONSIDERATIONS: Occluded fronts Occluded fronts offer worst possible weather! Avoid the apex of the occlusion by at least 50 to 100 miles. Circumnavigate to right (tailwinds). Do not fly through an occluded front. Wait, circumnavigate, or fly through stationary/warm front separately.

questions ?

Identify indications of frontal ELO Identify indications of frontal passage IAW FM 1-230.

On the ground wind shift Temperature Dew point pressure

In flight more difficult to recognize best indicator is OAT gauge anticipate drift correction to right (with possible exception of occlusion)

Property of Lear Siegler

Property of Lear Siegler

Property of Lear Siegler

Property of Lear Siegler

Property of Lear Siegler

Property of Lear Siegler

Property of Lear Siegler

Property of Lear Siegler

questions ?

Open Wave Warm Air Colder Cold Property of Lear Siegler

Practical Exercise

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