Hurricane Frances

MODIS view of Hurricane Frances (Note that eye is present but clouds at base of eye make it look cloudy throughout)

FRANCES TRACK

Hurricane frequency Frances

Hurricane Structure Major Components –Eye –Eyewall(s) –Rainbands (primary, secondary, outer) Regions –Core region –Outer region Other Components (not always present) –Eyewall mesovortices and swirls –Fine-scale rainbands

From Willoughby (1988) Structure of a hurricane: View from the top

Structure of a Hurricane in cross section

Theta-e from Simulation (Liu et al 1997) Conceptual

Light-shading: cloud and precipitation Dark regions: convective eyewall and spiral rainbands EIL: : Eye inversion layer (slash- hatched areas) OEA: occluded eye air with low  e (cross-hatched regions) MTD: moist downdrafts between the convective bands SR: Spiral rainband updrafts RO: Return outflow SU: Sloping updraft of eyewall MI: Main inflow MO: Main outflow RI: Return inflow DF: Divergent flow VC: Forced vertical circulation LX: Lateral mixing GO: Gravity wave oscillations MD: Mean decent in eye Dashed line: Freezing level Schematic (radial–height) conceptual model of a mature hurricane in the inner-core region

Types of eyewall structure observed in hurricanes with radar Symmetric single ring eyewall

The double eyewall of Hurricane Gilbert (1988) (most intense Category 5 storm in western hemisphere)

Asymmetric eyewall of Hurricane Georges

From Willoughby et al. (1984) Inner Core Region: PGF balances Centrifugal acceleration Inside eye, Rankine vortex Approx. ( v(r) = V o R/r ). Outside gradient wind approx. is valid: (v 2 /r + fv –fv g = 0) Parcels orbit eye inside core region

From Willoughby et al. (1984) Outside Core Region: Coriolis force Important Air passes around hurricane without orbiting Convergent airflow along the right flank relative to direction of motion (motion here to top of page)

Principal Band: primary band of precipitation - typically extending southeast from eyewall toward perimeter of hurricane

Connecting Band: Sometimes connects Eyewall to Principal Band

Compare the conceptual model to Hurricane Frances

Inner core of Frances Principal band

Radial velocity from Hurricane FrancesConceptual diagram The inner core winds of Hurricane Frances

Eyewall Mesovortices Wright and Bennett (1997) Bertha 1996 Isabel 2003

No suggestion of vortices in eye of Frances from satellite

Eye vortex

Gall et al. (1998) Hurricanes also contain many fine scale bands Hurricane Andrew (1992)

Hurricanes also contain many fine scale bands Hurricane Hugo (1989) Gall et al. (1998)

Note the fine scale bands in Andrew

Fine scale bands in Frances