flow channeling in the mohawk & hudson valleys a multiscale case study of surface flow...
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Flow Channeling In The Flow Channeling In The Mohawk & Hudson ValleysMohawk & Hudson Valleys
A Multiscale Case Study of A Multiscale Case Study of Surface Flow ConvergenceSurface Flow Convergence
Ninth Annual Northeast Regional Operational Workshop/NWS/CESTM
7-8 November 2007
Michael E. Augustyniak
Lance F. BosartDepartment of Earth and Atmospheric
Sciences, University at Albany State University of New York, Albany, New York
Hugh W. Johnson IVNOAA/NWS, Weather Forecast Office, Albany,
New York
Flow Channeling In The Mohawk Flow Channeling In The Mohawk & Hudson Valleys& Hudson Valleys
Known locally as Known locally as Mohawk-Hudson Mohawk-Hudson convergenceconvergence, it occurs when surface air , it occurs when surface air parcels traveling down the upper Hudson parcels traveling down the upper Hudson Valley (from north to south) meet air Valley (from north to south) meet air parcels traveling down the Mohawk Valley parcels traveling down the Mohawk Valley (from west to east)(from west to east)
Flow Channeling In The Mohawk Flow Channeling In The Mohawk & Hudson Valleys& Hudson Valleys
Low-level convergence generates a resurgence Low-level convergence generates a resurgence of precipitation behind departing low pressure, of precipitation behind departing low pressure, which is unrelated to lake effectwhich is unrelated to lake effect
Why study it?Why study it? ““Mohawk-Hudson convergence” tends not to be Mohawk-Hudson convergence” tends not to be
forecast very well by today’s models, which poses a forecast very well by today’s models, which poses a problem for forecastersproblem for forecasters
It tends to occur over the region’s population centersIt tends to occur over the region’s population centers The effects of a poor forecast are amplified when The effects of a poor forecast are amplified when
snowfall is involved, or during peak travel timessnowfall is involved, or during peak travel times
Case StudiesCase Studies
Discussed today:Discussed today: 27 Nov. 200227 Nov. 2002 (The day before Thanksgiving) (The day before Thanksgiving)
Studied as part of M.S. Thesis research:Studied as part of M.S. Thesis research: 16-17 Dec. 200216-17 Dec. 2002 23-24 Jan. 200323-24 Jan. 2003 17 Jan. 200517 Jan. 2005 03 Mar. 200603 Mar. 2006 28-29 Jan. 200728-29 Jan. 2007
Geography of New York & New EnglandGeography of New York & New England
Geography of New York & New EnglandGeography of New York & New England
Geography of New York & New EnglandGeography of New York & New England
27 November 200227 November 2002Case StudyCase Study
(The day before Thanksgiving)(The day before Thanksgiving)
Surface FeaturesSurface Features
1200 UTC 27 Nov. 2002
Albany, NY (ENX) Radar ImageryAlbany, NY (ENX) Radar Imagery
0958 UTC 27 Nov. 2002
Albany, NY (ENX) Radar ImageryAlbany, NY (ENX) Radar Imagery
1202 UTC 27 Nov. 2002
Albany, NY (ENX) Radar ImageryAlbany, NY (ENX) Radar Imagery
1400 UTC 27 Nov. 2002
Albany, NY (ENX) Radar ImageryAlbany, NY (ENX) Radar Imagery
1558 UTC 27 Nov. 2002
Albany, NY (ENX) Radar ImageryAlbany, NY (ENX) Radar Imagery
1803 UTC 27 Nov. 2002
Albany, NY (ENX) Radar ImageryAlbany, NY (ENX) Radar Imagery
2001 UTC 27 Nov. 2002
Albany, NY (ENX) Radar ImageryAlbany, NY (ENX) Radar Imagery
2229 UTC 27 Nov. 2002
Synoptic Overview (GFS)Synoptic Overview (GFS)
Synoptic Overview (GFS)Synoptic Overview (GFS)
Synoptic Overview (GFS)Synoptic Overview (GFS)
LL
Synoptic Overview (GFS)Synoptic Overview (GFS)
LL
Temp. Advection & Vertical Temp. Advection & Vertical Velocity (NARR)Velocity (NARR)
2100 UTC 27 Nov. 2002
Temp. Advection Profile (NARR)Temp. Advection Profile (NARR)
Vertical Motion Profile (NARR)Vertical Motion Profile (NARR)
Surface AnalysisSurface Analysis
2100 UTC 27 Nov. 2002
Sea Level PressureSea Level PressureSea Level Pressure
27-28 Nov. 2002
1016
1017
1018
1019
1020
1021
1022
1023
1024
12:00
13:00
14:00
15:00
16:00
17:00
18:00
19:00
20:00
21:00
22:00
23:00 0:
001:
002:
003:
00
Time (UTC)
SL
P (
hP
a)
KUCA KGFL KALB KPOU
Surface MeteogramSurface Meteogram
KUCA
KGFL
KALB
KPOU
KALB (72518) SoundingsKALB (72518) Soundings
Moist Boundary Layer
Moist Boundary Layer
1200 UTC 27 Nov. 2002 0000 UTC 28 Nov. 2002
Wind Direction During Wind Direction During Convergence EventsConvergence Events
6 Cases Total:6 Cases Total:Wind Direction For MHC Cases At KUCA/KSYR
(Occurrences Per 10° Wind Bin)
0
5
10
15000°
010°020°
030°
040°
050°
060°
070°
080°
090°
100°
110°
120°
130°
140°
150°
160°170°
180°190°
200°
210°
220°
230°
240°
250°
260°
270°
280°
290°
300°
310°
320°
330°
340°350°
Wind Direction For MHC Cases At KGFL(Occurrences Per 10° Wind Bin)
0
5
10000°
010°020°
030°
040°
050°
060°
070°
080°
090°
100°
110°
120°
130°
140°
150°
160°170°
180°190°
200°
210°
220°
230°
240°
250°
260°
270°
280°
290°
300°
310°
320°
330°
340°350°
Wind Direction During MHC Cases At KALB(Occurrences Per 10° Wind Bin)
0
5
10000°
010°020°
030°
040°
050°
060°
070°
080°
090°
100°
110°
120°
130°
140°
150°
160°170°
180°190°
200°
210°
220°
230°
240°
250°
260°
270°
280°
290°
300°
310°
320°
330°
340°350°
N=46
Wind Direction During Wind Direction During Convergence EventsConvergence Events
6 Cases Total:6 Cases Total: Wind Direction For MHC Cases At KUCA/KSYR(Occurrences Per 10° Wind Bin)
0
5
10
15000°
010°020°
030°
040°
050°
060°
070°
080°
090°
100°
110°
120°
130°
140°
150°
160°170°
180°190°
200°
210°
220°
230°
240°
250°
260°
270°
280°
290°
300°
310°
320°
330°
340°350°
Wind Direction For MHC Cases At KGFL(Occurrences Per 10° Wind Bin)
0
5
10000°
010°020°
030°
040°
050°
060°
070°
080°
090°
100°
110°
120°
130°
140°
150°
160°170°
180°190°
200°
210°
220°
230°
240°
250°
260°
270°
280°
290°
300°
310°
320°
330°
340°350°
Wind Direction During MHC Cases At KALB(Occurrences Per 10° Wind Bin)
0
5
10000°
010°020°
030°
040°
050°
060°
070°
080°
090°
100°
110°
120°
130°
140°
150°
160°170°
180°190°
200°
210°
220°
230°
240°
250°
260°
270°
280°
290°
300°
310°
320°
330°
340°350°
N=48
Wind Direction During Wind Direction During Convergence EventsConvergence Events
6 Cases Total:6 Cases Total: Wind Direction For MHC Cases At KUCA/KSYR(Occurrences Per 10° Wind Bin)
0
5
10
15000°
010°020°
030°
040°
050°
060°
070°
080°
090°
100°
110°
120°
130°
140°
150°
160°170°
180°190°
200°
210°
220°
230°
240°
250°
260°
270°
280°
290°
300°
310°
320°
330°
340°350°
Wind Direction For MHC Cases At KGFL(Occurrences Per 10° Wind Bin)
0
5
10000°
010°020°
030°
040°
050°
060°
070°
080°
090°
100°
110°
120°
130°
140°
150°
160°170°
180°190°
200°
210°
220°
230°
240°
250°
260°
270°
280°
290°
300°
310°
320°
330°
340°350°
Wind Direction During MHC Cases At KALB(Occurrences Per 10° Wind Bin)
0
5
10000°
010°020°
030°
040°
050°
060°
070°
080°
090°
100°
110°
120°
130°
140°
150°
160°170°
180°190°
200°
210°
220°
230°
240°
250°
260°
270°
280°
290°
300°
310°
320°
330°
340°350°
N=47
ConclusionsConclusions
Mohawk-Hudson convergence is a terrain-Mohawk-Hudson convergence is a terrain-induced mesoscale phenomenoninduced mesoscale phenomenon
In most of the cases studied, precipitation In most of the cases studied, precipitation associated with Mohawk-Hudson associated with Mohawk-Hudson convergence occurs under similar synoptic convergence occurs under similar synoptic conditions, including…conditions, including…
ConclusionsConclusions
The prior passage of a 500-hPa troughThe prior passage of a 500-hPa trough The absence of strong forcingThe absence of strong forcing
Weak or neutral 500-hPa vorticity advectionWeak or neutral 500-hPa vorticity advection Weak or neutral 700-hPa vorticity advection by the Weak or neutral 700-hPa vorticity advection by the
thermal windthermal wind Weak low-level cold air advectionWeak low-level cold air advection
A statically-stable atmosphere with a well-A statically-stable atmosphere with a well-mixed, moist boundary layermixed, moist boundary layer
ConclusionsConclusions Higher sea level pressure at KGFL than at KPOUHigher sea level pressure at KGFL than at KPOU Higher sea level pressure at KUCA (KSYR) than at Higher sea level pressure at KUCA (KSYR) than at
KPSFKPSF Usual surface configuration: “Reverse-S” isobar Usual surface configuration: “Reverse-S” isobar
pattern with zonally-oriented pressure ridge nosing in pattern with zonally-oriented pressure ridge nosing in over zonally-oriented pressure troughover zonally-oriented pressure trough
Allows simultaneous North/NE winds in upper Hudson Valley Allows simultaneous North/NE winds in upper Hudson Valley and WNW winds in the Mohawk Valleyand WNW winds in the Mohawk Valley
Light to moderate winds at 850-hPa and below Light to moderate winds at 850-hPa and below (generally 10 m(generally 10 m··ss-1-1 or less) or less)
ConclusionsConclusions
A greater understanding of the interactions of A greater understanding of the interactions of local terrain and overlying synoptic flows that local terrain and overlying synoptic flows that leads to Mohawk-Hudson convergence, such as leads to Mohawk-Hudson convergence, such as through this research, is necessary before one through this research, is necessary before one can reasonably expect to make an accurate can reasonably expect to make an accurate forecastforecast
Medium- and short-range forecasting of Medium- and short-range forecasting of precipitation caused by Mohawk-Hudson precipitation caused by Mohawk-Hudson convergence is possible, and limited only by convergence is possible, and limited only by human and/or model skill at forecasting the human and/or model skill at forecasting the overlying synoptic regimeoverlying synoptic regime
Impacts On Aviation WeatherImpacts On Aviation Weather
Prolonged period of IFRProlonged period of IFR Impact on aviation industryImpact on aviation industry Government Performance and Results Government Performance and Results
Act (GPRA) factored into our Terminal Act (GPRA) factored into our Terminal Forecasts (TAF)Forecasts (TAF)
Probability of Detection (POD) of Probability of Detection (POD) of correctly forecasting IFR is 0.63 correctly forecasting IFR is 0.63
False alarm (FAR) is 0.44False alarm (FAR) is 0.44 Critical for especially GA pilotsCritical for especially GA pilots
Impacts On The EconomyImpacts On The Economy
Part of National Weather Service mission Part of National Weather Service mission is the enhancement of the national is the enhancement of the national economy economy
Additional deployment of snow removalAdditional deployment of snow removal Whether or not to close schools and Whether or not to close schools and
businesses businesses
Dilemma Of The End Of Dilemma Of The End Of Millennium SnowstormMillennium Snowstorm
Heaviest elements of the snowstorm Heaviest elements of the snowstorm (meso-scale banding) came in earlier than (meso-scale banding) came in earlier than forecastforecast
Dry slot all but shut down snow by nightfall Dry slot all but shut down snow by nightfall (when we though it would be the heaviest) (when we though it would be the heaviest)
Then…Then…
Mohawk-Hudson enhanced precipitation Mohawk-Hudson enhanced precipitation appeared right after we decided to drop appeared right after we decided to drop the Winter Storm Warningthe Winter Storm Warning
An inch of fluffy snow nevertheless caused An inch of fluffy snow nevertheless caused slick roads after sunupslick roads after sunup
Saving grace – it was a Sunday!Saving grace – it was a Sunday!
Future WorkFuture Work
Develop an algorithm which uses overlying Develop an algorithm which uses overlying synoptic conditions to help forecast Mohawk-synoptic conditions to help forecast Mohawk-Hudson convergenceHudson convergence Integrate various meteorological parameters into Integrate various meteorological parameters into
AWIPS procedure so we can help identify if and when AWIPS procedure so we can help identify if and when Mohawk- Hudson convergence will take place Mohawk- Hudson convergence will take place
Investigate warm season cases (thus far Investigate warm season cases (thus far focused on cold ones, namely snowstorms)focused on cold ones, namely snowstorms)
Investigate “Null” casesInvestigate “Null” cases
Thank You!Thank You!
Questions?Questions?
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