1. Challenges in Convective Storm Prediction for the Coastal-Urban New York City-Long Island Brian A. Colle 1, Kelly Lombardo 2, John Murray 3, and Harrison Li 4 1 School of Marine and Atmospheric Sciences Stony Brook University – SUNY 2 Department of Marine Sciences University of Connecticut 3 NYC NOAA-National Weather Service 4 Harvard University NOAA Photo: 7 July 1976

2. Outline Motivation: Northeast US convective storm climatology and coastal tornadoes. NYC early AM EF2 tornado 7 August 2007. Decay versus non-decay quasi-linear convective systems near the SNE coast. Future changes in convective frequency using CMIP5 data and linear discriminate analysis (LDA).

3. Spatial Distribution of Northeast U.S. Convective Storms During the Warm Season (1996-2007) (Murray and Colle MWR 2011) Storm frequency per 15-min interval (shaded in percent) for a composite reflectivity 45 dBZ and cloud-to-ground lightning from April through September of 1996–2007. Radar Frequency > 45 dBZ (in percent) Lightning Frequency (per km 2 ) Composite Reflectivity Cloud to Ground Lightning X X

4. 3 2 1 4 5 54 1 2 3 45 dBZ Frequency per Warm Season for 5 Boxes Across Northeast U.S.

5. Tornado Climatology for NYC and Long Island (1950-2010): Tornado Climatology for NYC and Long Island (1950-2010): Colle et al. (2012) UTC

6. 8 August 2007 NYC EF2 Tornado 1022-1050 UTC (Colle et al. 2012) New York Daily News * * * * * * * * 1 2 Brooklyn Staten Is.

7. 3: 1300Z 8/7 4: 1600Z 8/7 5: 2300Z 8/77:1000Z 8/86: 0600Z 8/8 3 4 67 1 2 0600Z 8/7 1300Z 8/7 1000Z 8/8 August 7-8 2007 Storm Reports

8. 0300 UTC 8 August 2007 Low-mid level frontogenetical forcing and ascent increases during the evening hours over PA 950 winds, thetaE, Frontogenesis 700 mb Q-vector K/100km/3hr *10 -1

9. 400 hPa 600 hPa 800 hPa Pittsburgh, PA 7 August 1200 UTC 7 August 1200 UTC 8 August 1200 UTC 6 August 1200 UTC 500 Z, 800:600 lpse X

10. EML, Rapid Low-level Destabilization, and Increasing Shear in a Few Hours 0500 UTC 8 Aug 0830 UTC 8 Aug RUC 0300 UTC vs 0900 UTC 03Z03Z 1500 J/kg EWR ACARS

11. Role of Mesoscale Boundaries and Surface Circulation Surface: 1000 UTC 8 Aug 2007 1013 UTC 8 Aug 2007: DIX radar X

12. Benefit of TDWR Radar DIX 88-D 1030 UTC TJFK 1030 UTC

13. Evolution of Linear Convective Systems Near the Coast MAINTAIN 6/1/02 DECAY 7/23/02 Warm Season Linear Events (2002-2007) Categories: DECAY (32 cases): Decays at the coast SLOW DECAY (19 cases): Decay from coast to 100 km offshore. MAINTAIN (9 cases): Little change in linear system at least 100 km offshore. definition for decay: Clear weakening trend in the line for at least 30 minutes. For most cases, the continuous line became 50 dBZ. Use coastal point at ~0.75 o ahead of the center of the convective line to construct NARR composite (closest 3-h period before decay time).` See Lombardo and Colle (2012;2013) for Climo and WRF process study Maintain: 5/31/02 Decay: 7/23/02

14. Comparisons of MUCAPE (for parcel in lowest 180 hPa) and 0-3 km Shear max min 75% 25% DECAY SLOW DECAY MAINTAIN

15. 900-800 hPa Frontogenesis and 900 hPa Temp Adv DECAY SLOW DECAY MAINTAIN SLOW DECAY MAINTAIN

16. Changes in April-Sept Days With Environments Favoring Convective Storms Using Linear Discriminate Analysis and CMIP5 RCP8.5 (Li and Colle 2016) Use: PW 58 : Daily precipitable water using 850, 700, 500 hPa TDIFF 58 :Daily temp(850 hPa) – temp (500 hPa)  =daily average omega 500 and 700 hPa R^2 = 0.43 versus convective storm days validated using radar Li and Colle (2014) using 88D radar and NARR: 8.20 × 10 -5 (CAPESHEAR) + 0.0589(PRWTR) – 5.94(OMEGA) > 2.35 Li And Colle 2014: 1996-2007 used to train LDA

17. Historical Annual Storm Days Using 7 CMIP5 Models and NARR/CFSR Average PW 58 vs Storm Days  vs Storm Days

18. Future Annual Convective Environment Days and PW 58 Using 7 CMIP5 Future Storm Env. Days PW 58 Changes

19. Region 1 (SW PA) Region 2 (E LI) Future Warm Season Convective Environment Days (SW PA vs E Long Island)

20. Average CMIP5 Changes (2066-2095 minus 1976-2005) PW58 change (percent change shaded)  change (shaded and contoured) Vertical shear 500-850hPa percent change

21. Summary There is a diurnal progression of convective storm frequency from the interior NE (early afternoon) to the coastal ocean (at night). There is a diurnal progression of convective storm frequency from the interior NE (early afternoon) to the coastal ocean (at night). NYC-Long Island tornadoes are most frequent during late summer (August) and can occur from very early AM to early evening (0900-0000 UTC). NYC-Long Island tornadoes are most frequent during late summer (August) and can occur from very early AM to early evening (0900-0000 UTC). 7-8 August 2007 NYC tornado occurred along a mesoscale boundary, with destabilization from an EML + diabatic cooling, a nose of higher thetaE along the coast, and a LLJ. 7-8 August 2007 NYC tornado occurred along a mesoscale boundary, with destabilization from an EML + diabatic cooling, a nose of higher thetaE along the coast, and a LLJ. Using a statistical approach on daily CMIP5 data, there is a 20-40% increase in convective storm frequency over the NE. Large moisture uncertainty and did not include CIN. Using a statistical approach on daily CMIP5 data, there is a 20-40% increase in convective storm frequency over the NE. Large moisture uncertainty and did not include CIN.