MESOSCALE  SUB-STRUCTURE


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Composite radar image at 2120 UTC 5 February 2001 exhibiting a single band arcing though New England with a multiband structure evident off the southern New England coast. For an  animation of this event click here.

Forecast Applications

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Publications and Presentations

20th Conference on Weather Analysis and Forecasting (10-16 Jan. 2004)
"A Forecast Strategy for Anticipating Cold Season Mesoscale Band Formation Within Developing Extratropical Cyclones"

31st Conference on Radar Meteorology (6-12 Aug. 2003)
"An observational study of cold season mesoscale band formation in the Northeast United States."

19th Conference on Weather Analysis and Forecasting (12-16 Aug. 2002)
"A CLIMATOLOGICAL AND COMPOSITE STUDY OF COLD SEASON BANDED PRECIPITATION IN THE NORTHEAST UNITED STATES"
"ANALYSIS OF MESOSCALE BANDED FEATURES IN THE 5-6 FEBRUARY 2001 NEW ENGLAND SNOWSTORM
 

20th Conference on Weather Analysis and Forecasting (Jan 2004)
Cyclone Workshop (Sep 2003)
31st Conference on Radar Meteorology (Aug 2003)
4th Northeast Regional Operational Workshop (Nov 2002)
MidAtlantic Winter Storms Conference (Oct 2002)
19th Conference on Weather Analysis and Forecasting (Aug 2002)
Thesis presentation (July 2002)
2002 Spring CSTAR meeting (May 2002)
27th Annual Northeast Storm Conference (March 2002)
3rd Northeast Regional Operational Workshop  (November 2001)

Climatology

Band Classification Scheme

Choose each band type to see example animations
 
Table 1

Band Type

Band Description
Single Linear reflectivity feature > 250 km in length, ~20-100 km in width, with an intensity >30 dBz maintained for at least 2 h
Multibanded At least 3 finescale bands with periodic spacing and of the same spatial orientation, with intensities > 10 dBz over the background reflectivity, maintained for at least 2 h
Narrow cold-frontal Narrow (10-50 km), long (>300 km) band found along the surface cold front or in the warm sector with an intensity > 40 dBz maintained for at least 2 h
Transitory Radar feature that meets all respective criteria in a given category, except one (usually the lifetime)
Undefined Radar feature that is ambigous due to bright banding or incomplete radar data
Nonbanded None of the above criteria are met

Application of scheme to 5 cold seasons (1996-2001)

 
(Left) Map of the northeast U.S. with the domain of study outlined. Note that we were restricted to the U.S. radar network so the  portions of the Atlantic Ocean and southern Canada were not included in the study.

The band classification scheme (Table 1) was applied to significant precipitation systems during 5 cold seasons (October - April, 1996-2001). A significant precipitation system was defined as a system associated with > 25 mm of rain, or >15 cm liquid equivalent in the case of frozen precipitation, during a 24 h period in the northeast U.S. Such cases were identified by utilizing the Unified Precipitation Dataset (UPD)and the Daily Weather Maps Series. 111 significant precipitation cases were identified, but only 88 had complete radar coverage. The band classsification scheme was applied to these 88 cases. The results are shown in Table 2.

                                                                                                                Table 2

Case Type

Events

# of Cases

% of cases
Single 48 35 39
Multiband 29 23 26
Narrow cold-frontal 36 30 34
Transitory 40 28 32
Undefined 9 9 10
Nonbanded  --- 13 15

TOTAL

162

138*

156*
*Note: cases frequently exhibited more than one type of banded structure
 
(Above) Surface cyclone relative composites of the 48  single band event (top) and 29 multiband band event (bottom) distributions. The surface cyclone position is centered at the origin, and the axis of the single band at a representative time is draw as a solid black line. Multiband events are represented by shaded areas. Concentric circles are spaced at 100 km apart.

Synoptic Composites (NCEP/NCAR Reanalysis, 2.5x2.5 degree resolution)

Based on above band distribution, cases were stratified into 5 composite classes. All bands exhibiting a majority of their length in the northwest quadrant relative to the surface cyclone were identified as Northwest cases. This category was subdivided into bands occurring within 500 km of the surface low (Northwest 1 cases) and those occuring outside of 500 km (Northwest 2 cases).  Bands which exhibited a majority of their length to the east of the surface cyclone were identified as East cases, and cases which exhibited no mesoscale banding were classified as Nonbanded cases.

The composites are centered around band initiation, from 12 hours before to 12 hours after, with a 6 hour time step.

Multiband cases
     -animation
Northwest cases
    -animation
Northwest 1 cases
    -animation
Northwest 2 cases
    -animation
East cases
    -animation
Nonbanded cases
    -animation

Model Composites (Eta Model 80 km resolution) and Cross Sections

Composites were created from the appropriate Eta model analysis, 6 h forecasts for each composite class.
Six pannel summary animations for each composite class are provided at the respective links below.
Fields include:
(a) 1000 hPa heights ( solid) contoured every 30 m (~ 4 mb) and 1000 - 500 hPa thickness (dashed) contoured every 60 m.
(b) 850 hPa heights (solid) contoured every 30 m, temperature (dashed) contoured every 5 C, and temperature advecdtion
    (shaded) in  degrees C  day-1.
(c) 700 hPa heights (solid) contoured every 30 m, deformation (dotted) and Miller 2-D frontogenesis (positive areas shadded)
    in degrees C 100 km-1 3 h-1.
(d) 500 hPa heights (solid) contoured every 60 m, and absolute vorticity contoured every 4 s-1, shadded above 12 s-1.
(e) 300 hPa height (black solid) contoured every 120 m, and isotachs (black dashed) contoured every 5 m s-1, shadded above
    15 m s-1.
(f) 600 - 800 hPa layer vertical velocity (x 10-3 hPa s-1), shaded where negative according to scale.

Multiband cases
    -cross section
Northwest cases
    -cross section
Northwest-near cases
    -cross section
Northwest-far cases
    -cross section
East cases
    -cross section
Nonbanded cases
    -cross section
Northwest dissipation
 

Datasets

Case Anomaly Maps
Case listing
    -MSWord
    -ASCII