FRONTS (Chapter 11) Figure 11.12 A weather map showing surface-pressure systems, air masses, fronts, and isobars (in millibars) as solid gray lines. Large arrows in color show air flow. (Green-shaded area represents precipitation.) (Chapter 11)

FIGURE 11.14 A surface weather map showing surface-pressure systems, air masses, fronts, and isobars (in millibars) as solid gray lines. Large arrows in color show air flow. (Green-shaded area represents rain; pink-shaded area represents freezing rain and sleet; white-shaded area represents snow.)

Ben Franklin’s Storm (Nov. 2, 1743) 500 mb L Boston L Philadelphia

Norwegian Cyclone Model Page: 323 FIGURE 12.1 The idealized life cycle of a mid-latitude cyclone (a through f) in the Northern Hemisphere based on the polar front theory. As the life cycle progresses, the system moves northeastward in a dynamic fashion. The small arrow next to each L shows the direction of storm movement. (pp. 322–324)

Typical Cold Front Convective precipitation 50–100 mile wide band along front Page: 308 FIGURE 11.16 A closer look at the surface weather associated with the cold front situated in the southern United States in Fig. 11.15. (Solid gray lines are isobars. Green-shaded area represents rain; white-shaded area represents snow.)

Cold Front Cross-Section Page: 309 FIGURE 11.18 A vertical view of a model representing the weather across the cold front in Fig. 11.16 along the line X–X´.

Typical Warm Front “Overrunning” Clouds and precipitation precede surface front Stratiform clouds starting about 750 miles from front Stratiform precipitation starting about 350 miles from front “Overrunning” Page: 312 FIGURE 11.21 Surface weather associated with a typical warm front in winter. A vertical view along the dashed line P-P´ is shown in Fig. 11.22. (Green-shaded area represents rain; pink-shaded area represents freezing rain and sleet; white-shaded area represents snow.)

Warm Front Cross-Section Figure 11.19 Vertical view of clouds, precipitation, and winds across the warm front in Fig. 11.18 along the line P–P’.

Warm Front Cross-Section WARM AIR COLD AIR Figure 11.19 Vertical view of clouds, precipitation, and winds across the warm front in Fig. 11.18 along the line P–P’.

Page: 312 FIGURE 11.22 Vertical view of a model illustrating clouds, precipitation, and winds across the warm front in Fig. 11.21 along the line P–P’.

FIGURE 11. 22 The formation of a cold-occluded front. The faster-moving cold front (a) catches up to the slower-moving warm front (b) and forces it to rise off the ground (c). (Green-shaded area in (d) represents precipitation.)

FIGURE 11. 22 The formation of a cold-occluded front. The faster-moving cold front (a) catches up to the slower-moving warm front (b) and forces it to rise off the ground (c). (Green-shaded area in (d) represents precipitation.)

FIGURE 11. 22 The formation of a cold-occluded front. The faster-moving cold front (a) catches up to the slower-moving warm front (b) and forces it to rise off the ground (c). (Green-shaded area in (d) represents precipitation.)

OCCLUDED FRONTS Heavy precipitation along front FIGURE 11. 22 The formation of a cold-occluded front. The faster-moving cold front (a) catches up to the slower-moving warm front (b) and forces it to rise off the ground (c). (Green-shaded area in (d) represents precipitation.) OCCLUDED FRONTS Heavy precipitation along front Convective or stratiform Short duration

FIGURE 11. 22 The formation of a cold-occluded front. The faster-moving cold front (a) catches up to the slower-moving warm front (b) and forces it to rise off the ground (c). (Green-shaded area in (d) represents precipitation.)

Occluded Front Cross-Section (“Cold Occlusion”) FIGURE 11. 22 The formation of a cold-occluded front. The faster-moving cold front (a) catches up to the slower-moving warm front (b) and forces it to rise off the ground (c). (Green-shaded area in (d) represents precipitation.)

FIGURE 11. 22 The formation of a cold-occluded front. The faster-moving cold front (a) catches up to the slower-moving warm front (b) and forces it to rise off the ground (c). (Green-shaded area in (d) represents precipitation.)

“Warm Occlusion” FIGURE 11. 23 (at left) The formation of a warm-type occluded front. The faster-moving cold front in (a) overtakes the slower-moving warm front in (b). The lighter air behind the cold front rises up and over the denser air ahead of the warm front. Diagram (c) shows a surface map of the situation.

Figure 11.21 The formation of a warm-type occluded front. The faster-moving cold front in (a) overtakes the slower-moving warm front in (b). The lighter air behind the cold front rises up and over the denser air ahead of the warm front. Diagram (c) shows a surface map of the situation.

Occluded Front Cross-Section (“Warm Occlusion”) Figure 11.21 The formation of a warm-type occluded front. The faster-moving cold front in (a) overtakes the slower-moving warm front in (b). The lighter air behind the cold front rises up and over the denser air ahead of the warm front. Diagram (c) shows a surface map of the situation.

“Warm Occlusion” FIGURE 11. 23 (at left) The formation of a warm-type occluded front. The faster-moving cold front in (a) overtakes the slower-moving warm front in (b). The lighter air behind the cold front rises up and over the denser air ahead of the warm front. Diagram (c) shows a surface map of the situation.

Cold Occlusion Warm Occlusion FIGURE 11. 22 The formation of a cold-occluded front. The faster-moving cold front (a) catches up to the slower-moving warm front (b) and forces it to rise off the ground (c). (Green-shaded area in (d) represents precipitation.)

(QUASI-) STATIONARY FRONT Partly cloudy or cloudy with widespread stratiform precipitation

Cyclone Family Cold Air Warm Air (pp. 306–319)

Station Temp SLP trend CC Wind dir Dew point Precip A B C D E F Low Falling Cirrostratus SE Moderate No B Overcast, (nb)stratus No, chance light drizzle C Overcast, nb-stratus Slightly higher Continuous rain D Lower Falling then rising nb-stratus or c-nimbus NW to W Slightly lower (?) Mod-hvy rain showers E Rising Clearing NW F No clouds Lower, stabilizing

cP or mP (Atlantic) cP mT

Clouds

Precipitation