Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution
-
Upload
garrison-camacho -
Category
Documents
-
view
38 -
download
3
description
Transcript of Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution
![Page 1: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/1.jpg)
Case Studies of Warm Season Cutoff Cyclone Precipitation
Distribution
Jessica NajuchDepartment of Earth and Atmospheric Sciences
University at Albany, State University of New York
Advisors: Lance Bosart and Dan Keyser
NWS Focal Points: Tom Wasula and Ken LaPenta
![Page 2: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/2.jpg)
Introduction
• Forecasting heavy precipitation associated with warm season cutoff cyclones can be very challenging
• These challenges arise from physiographic features and from rapid changes in cutoff cyclone structure
• These forecasting problems are particularly difficult in the northeastern US
![Page 3: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/3.jpg)
Motivation
• Given these forecasting problems, there needs to be more understanding of the diverse precipitation patterns associated with cutoff cyclones
• These precipitation patterns lead to many unforecasted flash floods
• Continue previous warm season cutoff cyclone research done by Matt Novak (CSTAR)
![Page 4: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/4.jpg)
Literature Review
• Hawes, J. T. and S. J. Colucci, 1986: An Examination of 500 mb Cyclones and Anticyclones in National Meteorological Center Predication Models
• G. D. Bell, and L. F. Bosart, 1989: Climatology of Northern Hemisphere 500 mb Closed Cyclone and Anticyclone Centers
• M. J. Novak, 2002: Warm Season 500 hPa Closed Lows
• B. A. Smith, 2003: Cutoff Cyclones: A Global and Regional Climatology and Two Case Studies
![Page 5: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/5.jpg)
Focus
• Stratify precipitation distribution relative to cutoff cyclone tracks as identified in composites developed by Matt Novak (2002)
• Map/understand cutoff cyclone precipitation characteristics in composites especially in relation to terrain
• Document mesoscale precipitation signatures in case studies representative of each of the composites
![Page 6: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/6.jpg)
Warm Season Composite Mean Cutoff Cyclone Tracks M. Novak (2002)
![Page 7: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/7.jpg)
Focus Continued
• Understand role of terrain/low-level jet interactions in determining the precipitation distribution in case studies representative of each of the composites
• Use composites to look for changes in orientation of the cutoff in each case
• Assess precipitation signatures in terms of shear/CAPE profiles in selected case studies
![Page 8: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/8.jpg)
Climatology of Monthly Precipitation Distribution
• NCEP Unified Precipitation Dataset (UPD)
• 51 year dataset, daily observations from 12Z–12Z
• Each day a cutoff with precipitation passed through 34°-48°N and 60°-92°W
• June through September (1948-1998)
• Calculated daily precipitation and percentage of climatological precipitation
![Page 9: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/9.jpg)
Outer Domain
![Page 10: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/10.jpg)
inches/day
mm/day
![Page 11: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/11.jpg)
inches/day
mm/day
![Page 12: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/12.jpg)
inches/day
mm/day
![Page 13: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/13.jpg)
inches/day
mm/day
![Page 14: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/14.jpg)
inches/day
mm/day
![Page 15: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/15.jpg)
% of Climo
![Page 16: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/16.jpg)
% of Climo
![Page 17: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/17.jpg)
% of Climo
![Page 18: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/18.jpg)
% of Climo
![Page 19: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/19.jpg)
% of Climo
![Page 20: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/20.jpg)
Climatology of Monthly Tracks• Used NCEP/NCAR reanalysis dataset
• Plotted 500 hPa geopotential heights at 30 m intervals
• Tracked cutoff cyclones through a subjective hand analysis at 6 hour intervals (1980-1998)
• A cutoff cyclone was defined by one closed 500 hPa isoheight for at least 24 hours
![Page 21: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/21.jpg)
![Page 22: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/22.jpg)
Results of the Climatology• There is a general eastward shift of heavy precipitation due
to cutoff cyclones from June to September
• The most intense daily rainfall associated cutoff cyclones occurs in the month of August
• The highest percentage of precipitation due to warm season 500 hPa cutoff cyclones occurs in the month of June and the lowest in the month of August
• Daily precipitation associated with cutoff cyclones is most widespread along the Atlantic Coast
![Page 23: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/23.jpg)
Cases
1. 6/30/98-7/1/98
-Great Lakes Category of a Closed Low
2. 7/3/96-7/5/96
-Hudson Bay Category of a Closed Low
![Page 24: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/24.jpg)
Case: 6/30/98 – 7/1/98
• Great Lakes Category of a closed low
• Produced all types of significant weather, many tornadoes
• OH, WV, 6-10” of rain
• VT, NY flash floods
![Page 25: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/25.jpg)
Key Players of this Case• Region 1: Severe weather reports due to Midwest nocturnal
convection between 00Z and 09Z on 30 June 1998
• Region 2: Severe weather reports associated with a pre-frontal trough and warm sector between 06Z on 30 June 1998 and 14Z on 01 July 1998
• Huge swath of heavy precipitation fell over NY/PA border extending to Cape Cod
• Jet-dynamics well in place but no strong baroclinic zone present
• 500 hPa trough pivots from positive tilt to a slightly negative tilt
![Page 26: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/26.jpg)
![Page 27: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/27.jpg)
Maximum Precipitation:Woonsocket, RI3.58 inches/~91 mm
2-day precipitation (in) ending 12Z 1 July 1998
![Page 28: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/28.jpg)
980630/0000F00
1000 Hght (m) and 1000-500 Thickness (dam) 850 Hght (m) and Isotachs (m s-1)
500 Hght (dam) and Abs. Vorticity (x10-5 s-1) 250 Hght (dam) and Isotachs (m s-1)
![Page 29: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/29.jpg)
1000 Hght (m) and 1000-500 Thickness (dam) 850 Hght (m) and Isotachs (m s-1)
200 Hght (dam) and Isotachs (m s-1)500 Hght (dam) and Abs. Vorticity (x10-5 s-1)
980630/1200F00
![Page 30: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/30.jpg)
980701/0000F00
1000 Hght (m) and 1000-500 Thickness (dam) 850 Hght (m) and Isotachs (m s-1)
500 Hght (dam) and Abs. Vorticity (x10-5 s-1) 200 Hght (dam) and Isotachs (m s-1)
![Page 31: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/31.jpg)
National Composite LVL:1
30-Jun-98 08:00:00
L – Surface Low
V – 500 hPa Vort Max
Radar Composite LVL: 10800 UTC 30 June 1998
L
V1
V2
![Page 32: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/32.jpg)
L – Surface Low
L
V – 500 hPa Vort Max
V2
V1
Radar Composite LVL: 11300 UTC 30 June 1998
V3
![Page 33: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/33.jpg)
National Composite LVL:1
30-Jun-98 18:30:00
L
L – Surface Low
V – 500 hPa Vort Max
V1V2
L
Radar Composite LVL: 1 1830 UTC 30 June 1998
V3
![Page 34: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/34.jpg)
National Composite LVL:1
30-Jun-98 23:30:00
L
L – Surface Low
V – 500 hPa Vort Max
V1V2
L
Radar Composite LVL: 12330 UTC 30 June 1998
V3
![Page 35: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/35.jpg)
![Page 36: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/36.jpg)
![Page 37: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/37.jpg)
![Page 38: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/38.jpg)
V2
V1
![Page 39: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/39.jpg)
V2
V3
V1
![Page 40: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/40.jpg)
V2
V3
V1
![Page 41: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/41.jpg)
V3 V2
![Page 42: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/42.jpg)
Surface Pressure (hPa) Hand Analysis for 1200 UTC30 June 1998
![Page 43: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/43.jpg)
── Potential Temperature (C)---- Mixing Ratio g/kg
1200 UTC 30 June 1998
![Page 44: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/44.jpg)
── Potential Temperature (C)---- Mixing Ratio g/kg
1800 UTC 30 June 1998
![Page 45: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/45.jpg)
http://weather.uwyo.edu
![Page 46: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/46.jpg)
http://weather.uwyo.edu
![Page 47: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/47.jpg)
Conclusions of First Case Study
• Antecedent convective system over the OH/TN valley provides a moisture source for large swath of precipitation over NY/PA border
• Corridor of heaviest precipitation along NY/PA border and east to southeast New England falls near 200 hPa jet-entrance region and associated 500 hPa vorticity maximum
• Heavy rain is concentrated ahead of well defined surface trough but no strong baroclinic zone is present
![Page 48: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/48.jpg)
Conclusions of First Case Study Continued
• There is dynamical forcing as evident by strong jets and strong 700 hPa ascent
• Precipitation in northern NY and northern New England is likely driven by warm air advection as well as cyclonic vorticity advection beneath the 200 hPa jet
• Convection in eastern PA, NJ, and southeast NY, late on the 30th, occurs beneath the 200 hPa jet in conjunction with a strong low-level jet
![Page 49: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/49.jpg)
What to Watch for When Dealing with 500 hPa Cutoff Cyclones….
• Refer to climatology to be aware of favored areas as well as amount of heavy precipitation
• Pay attention to the location, speed, and track of cutoff cyclones using real time data
• Watch for upper- and lower-level jet dynamics (exit/entrance regions) juxtaposed with vorticity maxima
• Look for surface cyclone development creating low-level flows that draw in excess moisture
![Page 50: Case Studies of Warm Season Cutoff Cyclone Precipitation Distribution](https://reader035.fdocuments.in/reader035/viewer/2022062301/56813532550346895d9c9865/html5/thumbnails/50.jpg)
558 558
558
564
570
564 570
564570
250 hPa ↓ jet
250 hPa
↓ jet
250 hPa jet →
← heavy rain
↑ ← heavy rain
V1
↑ ← heavy rain
t + Δt
tt – Δt
V2
V1
V2
V3
V2V3