Abstract
Three sets of idealized, cloud-resolving simulations are performed to investigate the sensitivity of tropical cyclone (TC) structure and intensity to the height and depth of environmental vertical wind shear. In the first two sets of simulations, shear height and depth are varied independently; in the third set, orthogonal polynomial expansions are used to facilitate a joint sensitivity analysis. Despite all simulations having the same westerly deep-layer (200-850 hPa) shear of 10ms-1, different intensity and structural evolutions are observed, suggesting the deep-layer shear alone may not be sufficient for understanding or predicting the impact of vertical wind shear on TCs. In general, vertical wind shear that is shallower and lower in the troposphere is more destructive to model TCs because it tilts the TC vortex farther into the downshear-left quadrant. The vortices that tilt the most are unable to precess upshear and realign, resulting in their failure to intensify. Shear height appears to modulate this tilt response by modifying the thermodynamic environment above the developing vortex early in the simulations, while shear depth modulates the tilt response by controlling the vertical extent of the convective vortex. It is also found that TC intensity predictability is reduced in a narrow range of shear heights and depths. This result underscores the importance of accurately observing the largescale environmental flow for improving TC intensity forecasts, and for anticipating when such forecasts are likely to have large errors.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 2155-2175 |
| Number of pages | 21 |
| Journal | Monthly Weather Review |
| Volume | 144 |
| Issue number | 6 |
| DOIs | |
| State | Published - Jun 1 2016 |
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ASJC Scopus subject areas
- Atmospheric Science
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Idealized tropical cyclone responses to the height and depth of environmental vertical wind shear. / Finocchio, Peter M.; Majumdar, Sharanya J; Nolan, David S; Iskandarani, Mohamed.
In: Monthly Weather Review, Vol. 144, No. 6, 01.06.2016, p. 2155-2175.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Idealized tropical cyclone responses to the height and depth of environmental vertical wind shear
AU - Finocchio, Peter M.
AU - Majumdar, Sharanya J
AU - Nolan, David S
AU - Iskandarani, Mohamed
PY - 2016/6/1
Y1 - 2016/6/1
N2 - Three sets of idealized, cloud-resolving simulations are performed to investigate the sensitivity of tropical cyclone (TC) structure and intensity to the height and depth of environmental vertical wind shear. In the first two sets of simulations, shear height and depth are varied independently; in the third set, orthogonal polynomial expansions are used to facilitate a joint sensitivity analysis. Despite all simulations having the same westerly deep-layer (200-850 hPa) shear of 10ms-1, different intensity and structural evolutions are observed, suggesting the deep-layer shear alone may not be sufficient for understanding or predicting the impact of vertical wind shear on TCs. In general, vertical wind shear that is shallower and lower in the troposphere is more destructive to model TCs because it tilts the TC vortex farther into the downshear-left quadrant. The vortices that tilt the most are unable to precess upshear and realign, resulting in their failure to intensify. Shear height appears to modulate this tilt response by modifying the thermodynamic environment above the developing vortex early in the simulations, while shear depth modulates the tilt response by controlling the vertical extent of the convective vortex. It is also found that TC intensity predictability is reduced in a narrow range of shear heights and depths. This result underscores the importance of accurately observing the largescale environmental flow for improving TC intensity forecasts, and for anticipating when such forecasts are likely to have large errors.
AB - Three sets of idealized, cloud-resolving simulations are performed to investigate the sensitivity of tropical cyclone (TC) structure and intensity to the height and depth of environmental vertical wind shear. In the first two sets of simulations, shear height and depth are varied independently; in the third set, orthogonal polynomial expansions are used to facilitate a joint sensitivity analysis. Despite all simulations having the same westerly deep-layer (200-850 hPa) shear of 10ms-1, different intensity and structural evolutions are observed, suggesting the deep-layer shear alone may not be sufficient for understanding or predicting the impact of vertical wind shear on TCs. In general, vertical wind shear that is shallower and lower in the troposphere is more destructive to model TCs because it tilts the TC vortex farther into the downshear-left quadrant. The vortices that tilt the most are unable to precess upshear and realign, resulting in their failure to intensify. Shear height appears to modulate this tilt response by modifying the thermodynamic environment above the developing vortex early in the simulations, while shear depth modulates the tilt response by controlling the vertical extent of the convective vortex. It is also found that TC intensity predictability is reduced in a narrow range of shear heights and depths. This result underscores the importance of accurately observing the largescale environmental flow for improving TC intensity forecasts, and for anticipating when such forecasts are likely to have large errors.
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U2 - 10.1175/MWR-D-15-0320.1
DO - 10.1175/MWR-D-15-0320.1
M3 - Article
VL - 144
SP - 2155
EP - 2175
JO - Monthly Weather Review
JF - Monthly Weather Review
SN - 0027-0644
IS - 6
ER -