Analysis of Precipitation Distributions
Associated with Two Cool-Season
Cutoff Cyclones
Melissa Payer, Lance F. Bosart, Daniel Keyser
Department of Atmospheric and Environmental Sciences
University at Albany, SUNY
Neil A. Stuart and Thomas A. Wasula
NOAA/NWS, Albany, NY
NROW XI
5 November 2009
NOAA/CSTAR Grant NA07NWS4680001
Motivation
• Forecasting precipitation distributions associated with
500 hPa cool-season cutoff cyclones can be a challenge in
the Northeast
• Forecast uncertainties often arise due to variation in cutoff
speed and interaction with the complex topography in the
Northeast
• Identifying signatures differentiating between precipitation
distributions would help forecasters
Objectives
• Determine how synoptic and mesoscale features affect
precipitation distributions through several case studies of
difficult-to-forecast cutoffs as well as cutoffs associated with
varying precipitation distributions
• Identify common signatures differentiating between various
precipitation distributions
Data
• 1.0° GFS
• 2.5° NCEP–NCAR reanalysis data
– Climatologies created for 1979–2008
• Standardized anomalies fields were created from the
1.0° GFS analyses with respect to climatology
• 6-h National Precipitation Verification Unit (NPVU) QPE
Methodology
• Cool-season: Oct 1–Apr 30
• Analysis period: 2004/05–2008/09
• Cutoff domain: 35–52.5°N, 90–60°W
• Cutoff criteria:
– Duration > 12 h
– 30-m height rise in all directions
• Precipitation domain: New England, NY, PA, NJ
• Heavy precipitation: > 25 mm of precipitation over the Northeast in a
24-h period from 1200 UTC to 1200 UTC
Case Study 1: 8–9 March 2008
• Fast-moving cutoff
• Widespread flooding event with some icing reported in the
Adirondacks
• Numerical models showed considerable variability in
forecasting the cutoff 3–8 days prior to the event
• Forecasts confined the heavy precipitation to coastal
regions; however widespread heavy precipitation was
observed throughout much of the Northeast
8–9 March 2008 Cutoff
8–9 March 2008
500 hPa Mean Heights (dam)
and Track of Cutoff
8–9 March 2008
2-day NPVU QPE (mm)
080307/0000F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
080307/0600F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
080307/1200F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
080307/1800F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
080308/0000F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
080308/0600F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
080308/1200F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
080308/1800F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
080309/0000F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
080309/0600F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
080309/1200F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
080309/1800F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
080310/0000F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
1800 UTC 8 March
0000 UTC 9 March
6-h NPVU QPE (mm)
1800 UTC 8 March
0000 UTC 9 March
250 hPa Geo. Heights (dam, solid contour), Winds (ms-1, shaded), and
Divergence (x 10-5 s-1, dashed contour)
1800 UTC 8 March
0000 UTC 9 March
500 hPa Geo. Heights (dam, solid contour), Absolute Vorticity
(x 10-5 s-1, shaded), Absolute Vorticity Advection (x 10-5 s-1 3 h-1, dashed
contour), and Wind (kt, barbs)
1800 UTC 8 March
0000 UTC 9 March
700 hPa Geo. Heights (dam, solid contour), Temperature (°C, dashed contour),
Q-vectors (arrow), and Q-vector Convergence/Divergence (K m-2 s-1, shaded)
1800 UTC 8 March
0000 UTC 9 March
Surface MSLP (m, solid contour), 1000–500 Thickness (m, dashed contour),
and Precipitable Water (mm, shaded)
1800 UTC 8 March
0000 UTC 9 March
925 hPa Frontogenesis (K/(100 km * 3 h), shaded), Potential Temperature (K,
solid contour), and Wind (kt, barbs)
1800 UTC 8 March
0000 UTC 9 March
Standardized Anomaly of Precipitable Water (SD, shaded),
850 hPa Geo. Heights (dam, solid contour), and Precipitable Water (mm,
dashed contour)
8–9 March 2008 Summary
• Three primary regions of heavy precipitation:
– Precipitation maximum east of Lake Ontario due to lake effect
– North-south band of precipitation in eastern New York and western
New England collocated with strong cyclonic absolute vorticity
advection and favorable QG forcing for ascent associated with strong
Q-vector convergence
– Heavy precipitation over Cape Cod and Maine associated with
strong frontogenesis ahead of warm front
• Exit and entrance regions of upper-level jet streaks provided
favorable forcing for ascent
• Anomalous Atlantic moisture advected by low-level jet
contributed to heavy precipitation
Case Study 2: 2–3 February 2009
• Considered a forecast bust for the Northeast
• Numerical models exhibited large disagreement in the
speed and track of the cutoff, which directly impacted
forecasts of precipitation type and amount
• Heavy precipitation was forecast to occur with this event;
however most locations received less than 5 mm
t–108 h
t–96 h
t–90 h
NCEP Global Ensemble Forecast System Valid 090203/1200
Source: Grumm et al. (2009)
2–3 February 2009 Cutoff
2–3 February 2009
500 hPa Mean Heights (dam)
and Track of Cutoff
2–3 February 2009
2-day NPVU QPE (mm)
090201/1200F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
090201/1800F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
090202/0000F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
090202/0600F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
090202/1200F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
090202/1800F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
090203/0000F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
090203/0600F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
090202/1200F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
090203/1800F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
090204/0000F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
090204/0600F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
090204/1200F000
DT Potential Temperature (K, shaded), Winds (kt, barbs), and LL Relative
Vorticity (black contours), 500 hPa Heights and Absolute Vorticity (inset)
1800 UTC 3 February
0000 UTC 4 February
6-h NPVU QPE (mm)
1800 UTC 3 February
0000 UTC 4 February
250 hPa Geo. Heights (dam, solid contour), Winds (ms-1, shaded), and
Divergence (x 10-5 s-1, dashed contour)
1800 UTC 3 February
0000 UTC 4 February
500 hPa Geo. Heights (dam, solid contour), Absolute Vorticity
(x 10-5 s-1, shaded), Absolute Vorticity Advection (x 10-5 s-1 3 h-1, dashed
contour), and Wind (kt, barbs)
1800 UTC 3 February
0000 UTC 4 February
Surface MSLP (m, solid contour), 1000–500 Thickness (m, dashed contour),
and Precipitable Water (mm, shaded)
1800 UTC 3 February
0000 UTC 4 February
850 hPa Equiv. Potential Temperature (K, solid contour), Equiv. Potential
Temperature Advection (K 3 h-1, shaded), and Wind (kt, barbs)
1800 UTC 3 February
0000 UTC 4 February
Standardized Anomaly of Precipitable Water (SD, shaded),
850 hPa Geo. Heights (dam, solid contour), and Precipitable Water (mm,
dashed contour)
2–3 February 2009 Summary
• Precipitation forecast bust associated with phase error in the
location of the surface cyclone which developed farther east
than expected
• Exit and entrance regions of upper-level jet streaks provided
favorable forcing for ascent along the coast
• Low precipitable water values (< 10 mm) contributed to the
low precipitation amounts observed
Summary
8–9 March 2008:
2–3 February 2009:
• Fast-moving cutoff
• Cutoff stalled over the Great Lakes
• Widespread heavy precipitation
• Precipitation confined to coast
• Rapid cyclogenesis occurred over
NY
• Cyclogenesis occurred off the East
Coast
• Dual jet streaks over the Northeast • Dual jet streaks off the East Coast
• Anomalous moisture advected by
LLJ (PWAT +2 to +5 SD)
• Little moisture present in region
(PWAT < +1 SD)
 Forecast precipitation issues due
to rapid cyclogenesis
 Forecast precipitation issues due
to phase and intensity errors
Questions/Comments?
Slides Removed
Future Work
• Continue working on additional case studies
• Categorize cutoff days in order to identify common
signatures differentiating between various precipitation
distributions
• Develop conceptual models to delineate cutoffs which
produce certain precipitation distributions to be used in
the operational setting
Results
• 170 cutoff events identified
– average region duration of 35.7 hours
• 384 cutoff days total
– 164 days (42.7%) received precipitation > 25 mm (~1 in.)
– 57 days (14.8%) received precipitation > 50 mm (~2 in.)
1722 UTC 8 March
2121 UTC 8 March
1800 UTC 8 March
0000 UTC 9 March
Standardized Anomaly of 850 hPa Meridional Winds (SD, shaded),
850 hPa Geo. Heights (dam, solid contour), and Wind (kt, barbs)
1430 UTC 3 February
2100 UTC 3 February