High-resolution Observations and Model Simulations of the Life Cycle of an Intense Mesoscale Snowband over the Northeastern United States Reporter: Prudence Yi-Yun Chien Reference: Novak, D. R., B. A. Colle, and S. E. Yuter, 2008: High-resolution Observations and Model Simulations of the Life Cycle of an Intense Mesoscale Snowband over the Northeastern United States. Mon. Wea. Rev., 136, 1433–1456.
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High-resolution Observations and Model Simulations of the Life Cycle of an Intense Mesoscale Snowband over the Northeastern United States Reporter: Prudence.
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High-resolution Observations and Model Simulations of the Life Cycle
of an Intense Mesoscale Snowband over the Northeastern United States
Reporter: Prudence Yi-Yun Chien
Reference:
Novak, D. R., B. A. Colle, and S. E. Yuter, 2008: High-resolution Observations and Model Simulations of the Life Cycle of an Intense Mesoscale Snowband over the Northeastern United States. Mon. Wea. Rev., 136, 1433–1456.
=> Changes in ascent dominated changes in moisture
MD
-0.14
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• Band evolution=> forcing, stability, and moisture
• Forcing (MM5 results)(1) Band formation deepening of a midlevel trough Increase in deformation, convergence, and frontogenesis
(2 )Band dissipation midlevel trough less defined, and frontogenesis weakened Conditional stability led to weak frontal circulation
Summary and discussion
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Summary and discussion
• StabilityConventional thinking: CI and SI increase => band formationThis study: CI occurred before band formation~1.5h band formation: CI decrease & F2D increase
• W max & F2D maxPrevious study: W max locate on the warm side of F2D max ~50-200km This study: W max and F2D max are nearly coincident
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Summary and discussion
• Moisturesource: Atlantic Ocean (band formation)change of ascent => change of moisture
• QPFMM5 underforecast ~30% max preci. (Δx=4km)axis of heaviest preci. ~50km to the SE of the observation locationHigher horizontal model resolution => improvement QPF much better improvement on F2D, stability, and moisture
Thanks for your listening.&
Questions?
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Conditional instability (CI)
0
zes
0
zes
(Holton, 2004: An Introduction to Dynamic Meteorology (4 th Ed.), Fig9.10, p.294)
(2) Air parcel reach the LFC
0
zes
(1)
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Inertial instability (II)
Absolute momentum: M = fy - ug
(Holton, 2004: An Introduction to Dynamic Meteorology (4th Ed.), p.205)