The Challenge of Convective Forecasting: Cold Season Convection by

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The Challenge of Convective Forecasting Cold
Season Convectionby
Lance F. Bosart Department of Earth and
Atmospheric SciencesThe University at
Albany/SUNY/ES-2271400 Washington AvenueAlbany,
NY 12222
NCAR Colloquium on the Challenge of Convective
Forecasting 10-21 July 2006
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Source van den Broeke et al. (2005)
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Source van den Broeke et al. (2005)
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Source van den Broeke et al. (2005)
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Source van den Broeke et al. (2005)
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Source Blier and Batten (1994)
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Source Blier and Batten (1994)
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Source Blier and Batten (1994)
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Source Blier and Batten (1994)
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Source Hales (1985)
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Source Hales (1985)
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Source Hales (1985)
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Source Hales (1985)
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Source Reed and Blier (1986a)
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Source Reed and Blier (1986b)
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Source Reed and Blier (1986b)
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Source Reed and Blier (1986b)
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Source Reed and Blier (1986b)
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Source Reed and Blier (1986b)
GS 35-255
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Source Burke and Schultz (2004)
GS 35-255
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Source Burke and Schultz (2004)
GS 35-255
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Source Burke and Schultz (2004)
GS 35-255
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Source Burke and Schultz (2004)
GS 35-255
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Source Burke and Schultz (2004)
GS 35-255
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Source Burke and Schultz (2004)
GS 35-255
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Source Burke and Schultz (2004)
GS 35-255
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Source Burke and Schultz (2004)
GS 35-255
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Source Gyakum and Barker (1988)
GS 35-255
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Source Gyakum and Barker (1988)
GS 35-255
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Source Gyakum and Barker (1988)
GS 35-255
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Source Gyakum and Barker (1988)
GS 35-255
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Source Gyakum and Barker (1988)
GS 35-255
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Source Gyakum and Barker (1988)
GS 35-255
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Source Gyakum and Barker (1988)
GS 35-255
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Source Bosart and Seimon (1988)
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Source Bosart and Seimon (1988)
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Source Bosart and Seimon (1988)
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Source Bosart and Seimon (1988)
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Source Bosart and Seimon (1988)
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Source Bosart and Seimon (1988)
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Source Bosart and Seimon (1988)
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Source Bosart and Seimon (1988)
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Source Bosart and Seimon (1988)
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Source Bosart and Seimon (1988)
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Source Bosart and Seimon (1988)
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Source Bosart and Seimon (1988)
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Source Bosart and Seimon (1988)
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Motivation

• Understand physical mechanisms behind cool season
  (November March) tornado occurrence in the
  Southeast U.S.
• Understand role of mesoscale features in
  modifying large-scale environment to enhance or
  inhibit tornado development

Source Wasula et al. (2006)
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COMPOSITE TORNADO EVENT 0000-0600 UTC (n393,
Tornado point 32 N, 90 W)
500 hPa heights (solid, dam), vorticity (dashed,
x 10-5 s-1), vort. advection (shaded, x 10-10
s-2)
200 hPa heights (solid, dam), isotachs (shaded, m
s-1)
Source Wasula et al. (2006)
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COMPOSITE TORNADO EVENT 0000-0600 UTC (n393,
Tornado point 32 N, 90 W)
850 hPa heights (solid, m), temperature (dashed,
C), temp. advection (shaded, x 10-5 C s-1)
1000 hPa heights (solid, m), 1000-500 hPa thck
(dashed, dam), 700 hPa relative humidity ()
Source Wasula et al. (2006)
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COMPOSITE TORNADO EVENT 0000-0600 UTC (n393,
Tornado point 32 N, 90 W)
700 hPa heights (solid, m), vertical motion
(dashed and shaded, x 10-3 hPa s-1),
850-500 hPa lapse rate (dashedC), 850 hPa ?e
(shaded, K), 850 hPa winds
Source Wasula et al. (2006)
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SEVERE WEATHER REPORTS 22-23 February 1998
7 Tornadoes 3 F3 42 Fatalities 260 Injuries
Blue Wind gt 25.7 m s-1 Green Hail gt 1.91
cm Red Tornado
Source Wasula et al. (2006)
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23 February 1998 0000 UTC AVN Analysis
SFC
500 hPa
850 hPa
200 hPa
Source Wasula et al. (2006)
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Tampa Bay (TBW) Sounding and Hodograph 23
February 1998 0000 UTC
CAPE 2891 J/kg LI -9 C LCL 962 hPa
V (m s-1)
U (m s-1)
Source Wasula et al. (2006)
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Source Wasula et al. (2006)
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22/1815 UTC IR Satellite
Source Wasula et al. (2006)
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22/2115 UTC IR Satellite
23/0015 UTC IR Satellite
22/2345 UTC IR Satellite
Source Wasula et al. (2006)
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23/0015 UTC
22/2255 UTC
Source Wasula et al. (2006)
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23/0315 UTC
23/0145 UTC
Source Wasula et al. (2006)
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23/0530 UTC
Source Wasula et al. (2006)
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Source Wasula et al. (2006)
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Source Wasula et al. (2006)
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Source Wasula et al. (2006)
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SST gt 0 SSTlt0 LAND
Source Wasula et al. (2006)
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Source Wasula et al. (2006)
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The 9 Dec'05 Storm Motivation

• Deepened rapidly and more than anticipated.
• Significant mesoscale structure was observed.
• Some tropical-like" structure was present.
• Jet-cyclone interactions appeared to be two-way.

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AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE
TAUNTON MA 250 AM EST FRI DEC 9 2005 CROSS
SECTIONS STILL SHOW TREMENDOUS MID LEVEL
FRONTOGENESISIN THIS REGION WITH EXCELLENT
POTENTIAL FOR SLANTWISE CONVECTION/MESOSCALE
BANDING. THIS IS ALSO ZONE OF MAXIMUM SNOW
GROWTH. ONLY LIMITING FACTOR TO MAKING THIS
ABLOCKBUSTER EVENT CONTINUES TO BE SPEED OF
SYSTEM...SO ALTHOUGH IT'S GOING TO SNOW HARD FOR
SEVERAL HOURS FROM MIDMORNING INTO EARLY
AFTERNOON WITH SNOWFALL RATES OF 2" PER
HOUR...IT SHOULD NOT LAST LONG ENOUGH TO GIVE
WIDESPREAD TOTALS OVER 10". WE'LL PROBABLY GET
SOME THUNDER/LIGHTNINGREPORTS WITH THIS AS WELL.
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1745 UTC 9 Dec 2005
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1754 UTC 9 Dec 2005
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1954 UTC 9 Dec 2005
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Source http//www.atmos.albany.edu/facstaff/rmct
c/DTmaps/animSelect.php
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Source http//www.atmos.albany.edu/facstaff/rmct
c/DTmaps/animSelect.php
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Source http//www.atmos.albany.edu/facstaff/rmct
c/DTmaps/animSelect.php
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1500 UTC 9 December 2005
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1800 UTC 9 December 2005
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2000 UTC 9 December 2005
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Source http//www.ndbc.noaa.gov/station_realtime
.php?stationBUZM3
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1800 UTC 9 Dec 2005
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Source Matthew Greenstein
1800 UTC 9 Dec 2005
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Summary and Conclusions

• Example of explosive secondary cyclogenesis.
• High shear environment associated with a strong
  jet.
• Low CAPE environment associated with steep lapse
  rates aloft.
• Small elevated CAPE likely due to warm air
  crossing jet axis.
• Jet reconfigures in response to rapidly deepening
  storm.
• Frontogenetical forcing helps to maintain strong
  mesoscale snowband.
• Coastal front ahead of cyclone center evolves
  into a bent-back front.
• Cyclone had some attributes of a developing
  tropical storm.

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Cold Season Severe Weather Event of 13 February
2006

• Widespread wind damage in eastern New York and
  western New England.
• Measured peak wind of 85 kt in Saratoga Springs,
  New York.
• Damaging winds associated with bowing line
  segments.
• Example of a strongly forced, high-shear,
  low-CAPE severe weather event in absence of
  sunshine.
• Possible downward momentum transport in
  convective cores.
• May be similar to events described by van den
  Broeke et al. (2005).

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