The SydneyHobart Yacht Race Extratropical Cyclone - PowerPoint PPT Presentation
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The SydneyHobart Yacht Race Extratropical Cyclone
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2000: A synoptic/diagnostic study of the 1998 Sydney-Hobart ... Illuminating diagnosis - understanding - signals to look for - explanation for other events ... – PowerPoint PPT presentation
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Title: The SydneyHobart Yacht Race Extratropical Cyclone
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The Sydney-Hobart Yacht Race Extratropical Cyclone
- Meteorological diagnosis
- Graham Mills
- BMRC
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Full detail and commentary
- Mills,G.A., 2001 Mesoscale cyclogenesis in
reversed shear the 1998 Sydney-Hobart yacht
race storm. Aust. Meteor. Mag 50, 29-52. - Mills.G.A., 2000 A synoptic/diagnostic study of
the 1998 Sydney-Hobart yacht race storm a
warm-cored extratropical cyclone. Bureau of
Meteorology Research Centre Research Report No.
76. 65pp.
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Outline
- What happened - re-analyses from BOM99
- 5km model runs - independent verification for
MSLP and 10m wind - Synoptic Overview (75km LAPS analyses)
- Meso-scale diagnosis (5km model run) -
describe structure - model for secondary
development - Context of other studies
- Conclusions
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NWP data
- Operational LAPS analyses - use for synoptic
scale description - Operational meso-LAPS forecast - basis for
operational storm warning - Re-analysis at 0.375o/ 29 levels - includes new
analysis parameters - includes late data extra
cdw - basis for sensitivity studies - basis for
diagnosis of structure - Model runs at 0.75o, 0.375o, 0.25o, 0.125o, and
0.05o
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Mesoscale model summary
- Overall excellent forecast -upper
pattern -surface obs -MSLP ( ? Relative to
BOM99) - MSLP bias / modest deepening
- Complexity of low centres
- Strong wind band - strengthening in situ
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Large scale summary
- classic cutting off and negative tilting
- southerly jet and cva max
- Water-Vapour imagery
- northward development at msl
- frontal development and evolution
- role of Tasman low
- Large-scale processes maintaining strong wind band
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Mesoscale diagnosis - development
- IPV filament wrapping around -
cross-filament flow - Decreasing low-level static stability -
smaller Rossby radius/larger depth
of penetration - Scale of IPV filament/scale of isallobaric centres
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Mesoscale diagnosis - structure
- Frontogenesis
- Warm seclusion
- Warm core a result of advection and shallow
- Extreme llj in reversed shear flow
- Scale of 400 hPa easterly jet
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Western flank storms
- Hurricane-like storms in non-frontal trough
(Bergeron, 1920s) - Polar lows
- Reversed shear arctic front (type) polar lows
(Duncan) - Reed and Duncan - Gulf of Alaska -
Norwegian Sea (Gronas, 1995) - Australian cases - Sygna storm - Type 3 lows
- ALL WARM CORED ?
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Polar lows
- Short-wave / jet streak type - marked cva aloft
- Arctic front type - shallow baroclinicity,
strong surface fluxes, deep convection - Cold low type - weak barocinicity, strong
surface fluxes, deep convection - Reversed shear systems
- Combinations !!!!!!!!
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Hurricane like?
- Warm core - deep subsidence
- Rapid development - CISK
- Eye (?)
- Oceanic - are these theories developed to cope
with lack of sufficient data? - This case shows that bottom-up instability not
necessary
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Model sensitivities
- Late dataAnalysis parameters
- PBL
- RESOLUTION
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Summary
- Spectacular operational forecast
- Extreme event ( lt0.01)
- Illuminating diagnosis - understanding -
signals to look for - explanation for other
events
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Implications
- Users simplistic conceptual models- introduce
term such as western flank storm - Too much detail to communicate- scale of llj vs
scale of coastal waters forecast - NWP model progress
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