1. The Effect of Downsloping on Precipitation Distributions in the Capital District of New York State
Kyle J. Pallozzi and Lance F. Bosart
Department of Atmospheric and Environmental Sciences
University at Albany/SUNY
Albany, NY 12222
Robert Gaza
New York State Department of Environmental Conservation
Albany, NY 12233
NROW XV
Albany, NY
Wednesday 12 November 2014
Support Provided by: SUNY RF STEM
Undergraduate Research Grant

2. Background and Motivation
Terrain Influences in the Northeast
Rain shadowing in the Wyoming Valley of Pennsylvania
(Brady and Waldstreicher 2001)
1998 Mechanicville, NY tornadogenesis (LaPenta et al. 2005)
1995 Great Barrington, MA tornadogenesis (Bosart et al. 2006)
Severe weather distribution in eastern New York and western New England (Wasula et al. 2002)

3. Background and Motivation
Why should this be studied:
Topographic features play a large role in the Capital District’s weather
Past experience: Complicating factor in forecasting precipitation distributions during winter storms

4. Topographic Map of New York State
Taconics
Heldebergs
Greens
Berkshires
Catskills
Source: maps.com

5. Source: Western Regional Climate Center
KALB Wind Rose ( )
Source: Western Regional Climate Center

6. Hurricane Sandy Precipitation
Source: AHPS Precipitation Analysis
Source:ESRL

7. Hurricane Sandy Precipitation
Albany received only 3.3 mm (0.13 in) of precipitation
Source: Interior of Eastern New York Weather Observers

8. Objectives Seek predictors to address these questions:
When will downsloping events occur?
What will the magnitude of precipitation reduction be?
What will the westward extent of reduced precipitation be?
Want predictors to be operationally useful
Candidate predictors are:
850 hPa wind
925 hPa wind
Mean vector 850 hPa wind
Mean vector 925 hPa wind

9. Methodology

10. Data Focus of Study: Capital District (NY) KALB Radisonde Data
850 hPa and 925 hPa winds
NARR (North American Regional Reanalysis)
Mean vector 850 hPa and 925 hPa winds (3 h)
Focus of Study: Capital District (NY)
Problem: ASOS stations too widely spaced to provide precipitation data
Solution: Interior of Eastern New York Weather Observers
Network of observers in the Albany area run by Bob Gaza

11. Station Selections Reliable Observers
Oriented in a west-east line through Albany across varying terrain

12. Eastern New York Weather Observers
Location
Elevation (m)
165
438 15
213 1 97
187 84
146
196 13
451
50 km 15 1
187 13
165
146

13. Methodology Time period: 2002-2003 through 2012-2013
Criteria for an event
Greater than 0.5” (12.7 mm) of precipitation at location 165 or 15 (western locations)
October 15 through April 15
161 storms met criteria

14. Methodology Calculated mean 850 and 925 hPa vector winds (NARR)
Separated storms into twelve 30 degree bins
Composite precipitation totals in each bin at the locations
Repeated process for KALB radiosonde data
Examined four bins ( degrees) of data
Threshold: 20 kt for 850 hPa
Threshold: 15 kt for 925 hPa

15. Results

16. 850 hPa Mean Vector Wind vs. Precipitation (NARR)

17. 850 hPa Mean Vector Wind vs. Precipitation (NARR)

18. 850 hPa Wind Direction vs. Precipitation (RAOB)

19. 925 hPa Mean Vector Wind vs. Precipitation (NARR)

20. 925 hPa Mean Vector Wind vs. Precipitation (NARR)

21. 925 hPa Wind Direction vs. Precipitation (RAOB)

22. Concluding Remarks Sd
Results show that easterly winds at 850 hPa and 925 hPa lead to downsloping and reductions in precipitation totals for eastern portions of the study area
Overall pattern was generally what was expected
Very little difference in precipitation totals at locations 146 and 13

23. Future Work Sd
Examine other variables with the end goal of better addressing the exact magnitude and western extent of downsloping
Incorporate Radar Data
-potentially scale observed precipitation to radar estimates throughout the cases

24. Numerical Results (NARR)
Bin Average Precipitation and Standard Deviation (mm)
850 direction
#165
#15 #1
#187
#146
#13
events
0-30
17.1
18.2
19.1
20.3
32.5
31.6 5
2.7
2.93
3.07
7.44
9.07
10.5
30-60
37.6
35.8 34
28.7
34.4 8
20.9 18
17.6
14.4
14.3
60-90
74.6
58.2
48.6
42.4 36
38.6
23.9
21.2
16.1
16.5
15.5
90-120
46.7
41.1
35.4
32.3
30.4
31.1 13
29.1
22.4
20.7
23.6
20.8
19.2
33.4
34.2
29.9 25 22 11
17.4
16.8
11.1
8.62
31.3
34.1
30.3
26.4
24.1 23 24 19
18.9
18.3
27.2
28.4
28.6
26.6
26.7
26.1 43
15.2
14.8
14.2
14.6
14.9
22.5
22.1
21.4
26.3
27.8 30
11.2
12.4 12
15.6
16.6
20.4
18.7
25.5 14
8.87
8.84
10.7
14.7
12.7
17.8
16.9
8.29
4.95
4.28
4.94
6.78
12.6 37
35.7
35.3
43.1
42.6 2
7.18
2.33
1.62
3.59
21.7
17.5
13.7
9.14 1
925 direction
#165
#15 #1
#187
#146
#13
events
0-30
30.8
29.3
28.7
24.7
32.2
32.4 18
17.3 15
15.4
12.7
14.7
13.6
30-60 55
51.3
45.3
39.5
40.2
40.8 10
20.4
16.9
15.2
13.9
60-90
36.9
33.3
30.9
30.2
28.4 19
27.9
21.7
21.4
22.3
19.3
90-120
34.8
36.6
27.4
25.9
25.8 16
18.5
19.7
19.8 17 24
26.6
24.3
21.3
17.7
17.2 32
11.7
11.8
10.8
10.1
7.99
7.59
27.1
27.2 28
28.2
15.8
15.7
14.2
15.1
18.7
19.6
18.6 26
28.3
9.17
8.79
8.54
8.98
16.3
17.8
16.2
16.5
17.1
19.9 21 8
4.54
2.7
3.57
7.44
8.68
6.96
25.4
28.5
30.1
24.9
30.6
30.7 2
12.9
7.54
12.4
19.4
16.6
17.4
18.3 33 4
4.06
4.02
4.49
6.87
16.1
21.5
27.8
22.7
19.1
20.6
13.1
15.3
9.34
31.6
29.7
32.9
37.3 23
17.6
20.7

25. Numerical Results (RAOB)
Bin Average Precipitation and Standard Deviation (mm)
850 hPa
925 hPa
#165
#15 #1
#187
#146
#13
events
47.8 42
39.1
33.9
40.5
38.9 6
28.1
22.1
19.2
16.5
12.6
11.6
71.4
57.6
47.7
42.9
38.5
37.5 8
36.9
26.6
24.8
27.6
24.3
21.1
46.4
39.4
35.6
31.3
30.6
30.8 20
31.4
23.7
21.6
19.5
18.5 41
39.2
34.9
29.7
27.4 34
21.4
19.8
18.1
18.2
16.8
#165
#15 #1
#187
#146
#13
events
56.4
47.2
41.7
37.5
38.3
38.8 14
33.5 24
22.5
23.4
20.9
18.8
38.2
35.1
30.9
27.4
27.5 13
18.1
18.2
16.8
16.4
16.1
34.3
31.3
29.3 25
22.6
21.8 18
15.6
12.5
13.8
15.3 15
28.7
30.4
27.8
24.5
21.5
21.3 55
15.8
15.1
13.7
13.6
12.8
30-60
60-90
90-120

26. Numerical Results (Everything)
Bin Average Precipitation and Standard Deviation (mm)
850 direction
#165
#15 #1
#187
#146
#13
events
925 direction
0-30
17.1
18.2
19.1
20.3
32.5
31.6 5
30.8
29.3
28.7
24.7
32.2
32.4 18
2.7
2.93
3.07
7.44
9.07
10.5
17.3 15
15.4
12.7
14.7
13.6
30-60
37.6
35.8 34
34.4 8
47.8 42
39.1
33.9
40.5
38.9 6 55
51.3
45.3
39.5
40.2
40.8 10
56.4
47.2
41.7
37.5
38.3
38.8 14
20.9
17.6
14.4
14.3
28.1
22.1
19.2
16.5
12.6
11.6
20.4
16.9
15.2
13.9
33.5 24
22.5
23.4
18.8
60-90
74.6
58.2
48.6
42.4 36
38.6
71.4
57.6
47.7
42.9
38.5
36.9
33.3
30.9
30.2
28.4 19
38.2
35.1
27.4
27.5 13
23.9
21.2
16.1
15.5
26.6
24.8
27.6
24.3
21.1
27.9
21.7
21.4
22.3
19.3
18.1
16.8
16.4
90-120
46.7
41.1
35.4
32.3
30.4
31.1
46.4
39.4
35.6
31.3
30.6 20
34.8
36.6
25.9
25.8 16
34.3 25
22.6
21.8
29.1
22.4
20.7
23.6
20.8
31.4
23.7
21.6
19.5
18.5
19.7
19.8 17
15.6
12.5
13.8
15.3
33.4
34.2
29.9 22 11 41
39.2
34.9
29.7
21.3
17.7
17.2 32
27.8
24.5
21.5
17.4
11.1
8.62
11.7
11.8
10.8
10.1
7.99
7.59
15.8
15.1
13.7
12.8
34.1
30.3
26.4
24.1 23
27.1
27.2 28
28.2
18.9
18.3
15.7
14.2
28.6
26.7
26.1 43
18.7
19.6
18.6 26
28.3
14.8
14.6
14.9
9.17
8.79
8.54
8.98
16.3
17.8
26.3 30
16.2
19.9 21
11.2
12.4 12
16.6
4.54
3.57
8.68
6.96
25.5
25.4
28.5
30.1
24.9
30.7 2
8.87
8.84
10.7
12.9
7.54
19.4 33 4
8.29
4.95
4.28
4.94
6.78
4.06
4.02
4.49
6.87 37
35.7
35.3
43.1
42.6
22.7
20.6
7.18
2.33
1.62
3.59
13.1
9.34
17.5
9.14 1
32.9
37.3