High Wind Relative Composites

Another facet of my research involves focusing on events, derived from the High Wind Climatology, that affected the Northeast Domain. An event is simply defined as a series of at least 2 high wind reports that are separated by less than or equal to 12 hour. The events were then categorized as being either Pure Convective, Pure Gradient, or Hybrid. If an event contained no gradient wind reports it was considered Pure Convective. Likewise if the event contained no thunderstorm wind reports it was considered a Pure Gradient event. Also, every gradient wind report associated with each Pure Gradient event was checked if a lightning strike occurred within 1 hour and 1 degree latitude/longitude. If lightning did occur within 1 hour and 1 degree, the Pure Gradient event was considered a Hybrid event. Finally, if the event contained both gradient and thunderstorm wind reports it was considered a Hybrid event. The Hybrid and Pure Gradient events were further categorized according to where the initial Northeast report occurred relative to the surface cyclone. The subcategories for Hybrid and Pure Gradient events are Southeast, Northeast, Northwest, and Southwest quadrants. The Pure Convective events were subcategorized according to whether or not a 300 hPa trough or ridge was present in the vicinity of the initial report. The subcategories were appropriately name Trough or Ridge Pattern.

These criteria produced a total of 335 high wind events, 123 of which were considered Hybrid, 165 Pure Gradient, and 47 Pure Convective. I then composited all of these based on event type. The grid for each event was shifted so that it was centered on the location of the first occurrence of high wind in the Northeast. The grids were then averaged and centered on the centroid of all of the initial occurrences of high wind in the Northeast, essentially creating a high wind relative composite. The time of the event composited was chosen to be the hour, either 0000, 0600, 1200, or 1800 UTC, closest to the time of the initial occurrence of high wind in the Northeast. If the initial occurrence happened on the midpoint between two of these hours, the earlier hour was chosen to be composited.

Below are a series of figures produced depicting general differences in structure of each event type. The star in each figure is the location of the centroid of all initial occurrences of high wind for each event type.

Here is the presentation I gave for my fellow research assistants on 21 October 2009:

Hybrid Event Composites

Southeast Composite (N = 71):
    Location of Composite Initial Occurrence of High Wind (black star), Mean Sea Level Pressure (hPa, black contours), Precipitable Water (mm, shaded), 1000-500 hPa Thickness (dam, red dashed), and 1000 hPa Total Wind (m/s, barbs): [LINK]
Northeast Composite (N = 30):
    Location of Composite Initial Occurrence of High Wind (black star), Mean Sea Level Pressure (hPa, black contours), Precipitable Water (mm, shaded), 1000-500 hPa Thickness (dam, red dashed), and 1000 hPa Total Wind (m/s, barbs): [LINK]
Northwest Composite (N = 8):
    Location of Composite Initial Occurrence of High Wind (black star), Mean Sea Level Pressure (hPa, black contours), Precipitable Water (mm, shaded), 1000-500 hPa Thickness (dam, red dashed), and 1000 hPa Total Wind (m/s, barbs): [LINK]
Southwest Composite (N = 14):
    Location of Composite Initial Occurrence of High Wind (black star), Mean Sea Level Pressure (hPa, black contours), Precipitable Water (mm, shaded), 1000-500 hPa Thickness (dam, red dashed), and 1000 hPa Total Wind (m/s, barbs): [LINK]

Pure Gradient Event Composites

Southeast Composite (N = 45):
    Location of Composite Initial Occurrence of High Wind (black star), Mean Sea Level Pressure (hPa, black contours), Precipitable Water (mm, shaded), 1000-500 hPa Thickness (dam, red dashed), and 1000 hPa Total Wind (m/s, barbs): [LINK]
Northeast Composite (N = 33):
    Location of Composite Initial Occurrence of High Wind (black star), Mean Sea Level Pressure (hPa, black contours), Precipitable Water (mm, shaded), 1000-500 hPa Thickness (dam, red dashed), and 1000 hPa Total Wind (m/s, barbs): [LINK]
Northwest Composite (N = 32):
    Location of Composite Initial Occurrence of High Wind (black star), Mean Sea Level Pressure (hPa, black contours), Precipitable Water (mm, shaded), 1000-500 hPa Thickness (dam, red dashed), and 1000 hPa Total Wind (m/s, barbs): [LINK]
Southwest Composite (N = 55):
    Location of Composite Initial Occurrence of High Wind (black star), Mean Sea Level Pressure (hPa, black contours), Precipitable Water (mm, shaded), 1000-500 hPa Thickness (dam, red dashed), and 1000 hPa Total Wind (m/s, barbs): [LINK]

Pure Convective Event Composites

Trough Pattern Composite (N = 34)
    Location of Composite Initial Occurrence of High Wind (black star), Mean Sea Level Pressure (hPa, black contours), Precipitable Water (mm, shaded), 1000-500 hPa Thickness (dam, red dashed), and 1000 hPa Total Wind (m/s, barbs): [LINK]
Ridge Pattern Composite (N = 9):
    Location of Composite Initial Occurrence of High Wind (black star), Mean Sea Level Pressure (hPa, black contours), Precipitable Water (mm, shaded), 1000-500 hPa Thickness (dam, red dashed), and 1000 hPa Total Wind (m/s, barbs): [LINK]

Research