1. Climatology of Inverted Troughs over the Gulf of Maine
Joseph Cebulko, Jason Cordeira, Justin Arnott, and Lance Bosart

2. Motivation

3. Base reflectivity (dBZ)
Cyclones that contain ITs deviate from traditional cyclone models
ITs may produce poorly forecast “surprise” snow events
Little previous research

7. Background

8. Cool Season Phenomena
Weisman et al. 2002

9. What is an IT?
Elongated region of relatively low atmospheric pressure extending north/westward from a parent low over Northwest Atlantic
Has ability to focus and lift moisture in an unstable atmosphere resulting intense/persistent snow squalls (Lundstedt 1993)

10. ITs over the Gulf of Maine
5 Criteria for Significant Snowfall Production (Lundstedt 1993)
Surface-to-850-hPa ΔT ≥ 10°C
Boundary Layer RH > 50% with wind component from off the ocean on one side of the IT
500-hPa positive AVOR advection observed with 700-hPa UVM
Quasi-stationary IT axis for ~6 hours
850-hPa flow is weak OR parallel to surface IT

11. Data and Methodology

12. Data and IT Examples North American Regional Reanalysis dataset (NARR)
Plotted MSLP at 3-hr intervals Sept-May
Subjective analysis of objectively analyzed reanalysis data
Subset data by orientation for composite analyses
IT max amplification and study area

13. Precipitation and ITs
United States Unified Precipitation dataset (UPD)

14. Climatology

15. Annual Climatology

16. Monthly Climatology

17. K-means Clustering
k=2

18. K-means Clustering
k=2

19. K-means Clustering
k=2

20. Two Scenarios
NW-SE oriented ITs
W-E oriented ITs

21. Headlines issued on 36 of 57 (~63%) IT precip days
57 of 83 IT days (~69%)
(avg ~19 mm)
~8–10 inches
Headlines issued on 36 of 57 (~63%) IT precip days

22. Climatology Summary Data suggest that ITs are cool season phenomena
Majority of IT-influenced precipitation impacts the central Maine coast
Precipitation (~19 mm) observed on ~69% of days with an IT
Majority of ITs with precipitation are headlined (~63%)
Data suggests High-Impact Sub-Advisory (HISA) characteristic of ITs

23. Composite Life Cycle

24. t − 12 h 500-hPa Heights/Winds/AVOR 700-hPa Heights/Winds/UVM
(×10−5 s−1; shaded according to scale)
(hPa s−1; shaded according to scale)
MSLP & 10-m winds/divergence
(s−1; shaded according to scale)

25. t − 12 h 850-hPa Heights/Temps/Q-Vectors/QDIV
950-hPa Heights/Winds/Temps/FGEN
[shaded; K (100 km)−1 3 h−1]
MSLP & 10-m winds/divergence
(s−1; shaded according to scale)

26. t − 0 h 500-hPa Heights/Winds/AVOR 700-hPa Heights/Winds/UVM
(×10−5 s−1; shaded according to scale)
(hPa s−1; shaded according to scale)
MSLP & 10-m winds/divergence
(s−1; shaded according to scale)

27. t − 0 h 850-hPa Heights/Temps/Q-Vectors/QDIV
950-hPa Heights/Winds/Temps/FGEN
[shaded; K (100 km)−1 3 h−1]
MSLP & 10-m winds/divergence
(s−1; shaded according to scale)

28. t + 12 h 500-hPa Heights/Winds/AVOR 700-hPa Heights/Winds/UVM
(×10−5 s−1; shaded according to scale)
(hPa s−1; shaded according to scale)
MSLP & 10-m winds/divergence
(s−1; shaded according to scale)

29. t + 12 h 850-hPa Heights/Temps/Q-Vectors/QDIV
950-hPa Heights/Winds/Temps/FGEN
[shaded; K (100 km)−1 3 h−1]
MSLP & 10-m winds/divergence
(s−1; shaded according to scale)

30. Composite Analysis: Summary
Robust forcing for UVM extending away from parent low, confirmed by Q-Vector convergence
Frontogenesis ≥ 4 K (100 km)−1 3 h−1 within IT
Speed and directional wind convergence along IT axis
Life cycle requires < 24 h for completion

31. Operational Implications

32. Concluding Remarks
This study created a climatology of ITs over Gulf of Maine
Synoptic-scale processes lead to development/orientation of ITs
Mesoscale processes influence IT precipitation (headline vs no- headline)
New England WFOs will be able utilize this research in operational applications
Plethora of avenues for future work
Thank you!