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Titre du document / Document title

Extreme Helicity and Intense Convective Towers in Hurricane Bonnie

Auteur(s) / Author(s)

MOLINARI John (1) ; VOLLARO David (1) ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

(1) Department of Earth and Atmospheric Sciences, University at Albany, State University of New York, Albany, New York, ETATS-UNIS

Résumé / Abstract

Helicity was calculated in Hurricane Bonnie (1998) using tropospheric-deep dropsonde soundings from the NASA Convection and Moisture Experiment. Large helicity existed downshear of the storm center with respect to the ambient vertical wind shear. It was associated with veering, semicircular hodographs created by strong, vortex-scale, radial-vertical flow induced by the shear. The most extreme values of helicity, among the largest ever reported in the literature, occurred in the vicinity of deep convective cells in the downshear-left quadrant. These cells reached as high as 17.5 km and displayed the temporal and spatial scales of supercells. Convective available potential energy (CAPE) averaged 861 J kg-1 downshear, but only about one-third as large upshear. The soundings nearest the deep cells were evaluated using two empirical supercell parameters that make use of CAPE, helicity, and/or shear. These parameters supported the possible existence of supercells as a consequence of the exceptional helicity combined with moderate but sufficient CAPE. Ambient vertical wind shear exceeded 12 m s-1 for 30 h, yet the hurricane maintained 50 m s-1 maximum winds. It is hypothesized that the long-lived convective cells enabled the storm to resist the negative impact of the shear. Supercells in large-helicity, curved-hodograph environments appear to provide a useful conceptual model for intense convection in the hurricane core. Helicity calculations might also give some insight into the behavior of vortical hot towers, which share some characteristics with supercells.

Revue / Journal Title

Monthly weather review    ISSN  0027-0644   CODEN MWREAB 

Source / Source

2008, vol. 136, no11, pp. 4355-4372 [18 page(s) (article)] (1 p.1/2)

Langue / Language

Anglais

Editeur / Publisher

American Meteorological Society, Boston, MA, ETATS-UNIS  (1872) (Revue)

Mots-clés anglais / English Keywords

Tropical cyclone

;

models

;

winds

;

Available potential energy

;

Supercell

;

Convection cell

;

Vertical flow

;

Radial flow

;

Vortex

;

Hodograph

;

Wind shear

;

storms

;

Dropsonde

;

troposphere

;

hurricanes

;

Helicity

;

extreme value

;

Mots-clés français / French Keywords

Cyclone tropical

;

Modèle

;

Vent

;

Energie potentielle disponible

;

Supercellule

;

Cellule convection

;

Ecoulement vertical

;

Ecoulement radial

;

Tourbillon

;

Hodographe

;

Cisaillement vent

;

Tempête

;

Radiosonde parachutée

;

Troposphère

;

Ouragan

;

Hélicité

;

Valeur extrême

;

Mots-clés espagnols / Spanish Keywords

Ciclón tropical

;

Modelo

;

Viento

;

Energía potencial disponible

;

Supercélula

;

Célula convección

;

Flujo vertical

;

Flujo radial

;

Torbellino

;

Hodógrafo

;

Cizallamiento viento

;

Tempestad

;

Radiosonda con paracaídas

;

Huracán

;

Helicidad

;

Localisation / Location

INIST-CNRS, Cote INIST : 141, 35400018433517.0200

Nº notice refdoc (ud4) : 20841487



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