1. Waterspout Forecasting A Gulf Coast Perspective and Modern Day Look Jeffrey M. Medlin NOAA - NWS Forecast Office Mobile, AL Jeffrey F. Garmon NOAA – NWS Forecast Office Cheyenne, WY

2. Tornado over the water… Possesses a parent mesocyclone: a much different animal. Image Courtesy of WKRG TV, Mobile AL

3. Waterspouts… Wind speeds are more often under 100 KT. But…even these weaker circulations can cause damage and injury. [EF0 -> 65-85 mph, EF1-> 86- 100 mph – most of what I’ve seen in 20+ years!] On days of deeper instability forming over zones of stronger convergence…they can become quite strong with winds over 100 KT…posing a much greater hazard. Several documented cases of waterspouts producing EF1/F-1 damage.

4. Tornadoes form under two regimes (Fujita, 1981) Mesocyclone (diameter >4 km) “Supercell”Mesocyclone (diameter >4 km) “Supercell” Misocyclone (diameter < 4 km) “Non-Supercell”Misocyclone (diameter < 4 km) “Non-Supercell” Misocyclone circulations are the most probable mode of formation for: “landspouts” (Bluestein, 1985) and“landspouts” (Bluestein, 1985) and “waterspouts” (Wakimoto and Wilson, 1988).“waterspouts” (Wakimoto and Wilson, 1988). Mesocyclone versus Misocyclone

5. Not a gustnado either!... Gustnado along a fast-moving squall line (M59 kt) Orange Beach, AL 25 Apr 2015 – 2044 UTC Although some similarities!

6. Radar Observation of the Circulation Waterspout circulation is much more shallow and is smaller…therefore it will involve significant sampling issues due to beam elevation and beam width with range. Aspect Ratio (core dia. / beam width) prevents sampling of the phenomena much beyond 40 km In sample “A”…SW values would likely be high…a tip off!

7. Climatology… NWS Storm Data – NCDC database period 1995-2007 Mobile, Baldwin, Escambia, Santa Rosa, and Okaloosa Counties

8. Landfalling waterspouts reported as tornadoes… A significant number of the warm season coastal “tornadoes” in the historical database are in fact land-falling “fair weather” waterspouts.

9. Landfalling waterspouts reported as tornadoes… A preliminary study conducted back in the 2003- 2007 time frame revealed over half the time, when one waterspout was reported there were two or more (unpublished, Medlin and Caceres). There is a reason for this!There is a reason for this!

10. 28.12 UTC Textbook Example of Land and Sea-Breeze Circulation Reversal Note how land breeze has shape of the western Florida Peninsula Coastline and it translates northwestward while becoming less defined with time as heating occurs in its wake. Offshore – directed lower branch of land breeze circulation. 28 June 2012 – 12-16 UTC

11. 28.14 UTC

12. 28.15 UTC First evidence of new sea-breeze ***Note*** wind reversal to “onshore” at a few locations along western FL coastline

13. 28.16 UTC 28.13 UTC Position

14. Waterspouts… Formation aided by… Formation aided by… pre-existing vertical vorticity maxima (e.g., existing along a nocturnal land breeze boundary) which become coincident with… pre-existing vertical vorticity maxima (e.g., existing along a nocturnal land breeze boundary) which become coincident with… low-level updrafts with TCu forming along the boundary.low-level updrafts with TCu forming along the boundary. Waterspouts have been observed to occur along thunderstorm outflow boundaries and are formed by a similar process. Waterspouts have been observed to occur along thunderstorm outflow boundaries and are formed by a similar process. Another requirement for their occurrence is unstable airmass which enhances boundary layer updrafts, resulting in vortex stretching. Another requirement for their occurrence is unstable airmass which enhances boundary layer updrafts, resulting in vortex stretching.

15. Misocyclone formation… Wakimoto and Wilson, 1989 In the case of most waterspouts…these boundaries can be an attendant land-breeze, seabreeze, or outflows from nearby convection.

16. Misocyclonic formation… Wakimoto and Wilson, 1989 See the link!

17. How most waterspouts form… Brady and Szoke, 1989 Land-breeze or intersecting outflow boundaries establish zone of weak low level horizontal circulation of weak low level horizontal circulation “Convergence”

18. How most waterspouts form… Brady and Szoke, 1989 TCu forms along the convergent line…and updrafts with the TCu lift and stretch the horizontal circulation into the vertical. Vertical Advection of Circulation “Vertical Advection of Circulation”

19. How most waterspouts form… Brady and Szoke, 1989 As the updraft increases, it stretches, tightens and strengthens the vortex. As the vortex velocity increases the condensation funnel forms. “Stretching”

20. Waterspout – 29 Aug 2003 – Downtown Mobile, Alabama

21. Landspout – 14 June 2009 – Montgomery, Alabama Formed on a Progressive Derecho’s Gust Front! Photo courtesy Jennah Medlin

22. “Favored” Synoptic Environment for Waterspouts… Deep layer ridging resulting in light winds surface to mid- levels Deep layer ridging resulting in light winds surface to mid- levels Moderate CAPE (especially packed low in sounding) Moderate CAPE (especially packed low in sounding) Steep low level lapse rates Steep low level lapse rates Moist airmass (PW 1.7 - 2 inches) Moist airmass (PW 1.7 - 2 inches) Presence of convergence zones (outflow boundaries, landbreeze) Presence of convergence zones (outflow boundaries, landbreeze)

23. Choy and Spratt (1994) identified some conditions forecasters should look for… WIND Boundary layer (0-1.0 kft): 8 knots or less 975-700 mbs (1.5-10.0 kft): all levels 16 knots or less 699-600 mbs (10.5-14.0 kft): all levels 20 knots or less 599-500 mbs (14.5-18.0 kft): all levels 22 knots or less WIND Boundary layer (0-1.0 kft): 8 knots or less 975-700 mbs (1.5-10.0 kft): all levels 16 knots or less 699-600 mbs (10.5-14.0 kft): all levels 20 knots or less 599-500 mbs (14.5-18.0 kft): all levels 22 knots or less MOISTURE Precipitable Water value: 1.7 inches or more. MOISTURE Precipitable Water value: 1.7 inches or more.

24. Essential Tools Include… RAOBs RAOBs 88D 88D VWPVWP Z SWSW SRM (limited)SRM (limited) Higher resolution satellite imagery Higher resolution satellite imagery Early morning low cloud channelEarly morning low cloud channel Daytime visibleDaytime visible Surface observations Surface observations Tap into local mesonet and offshore dataTap into local mesonet and offshore data Coastal spotter network Coastal spotter network U.S. Coast Guard (reports from VHF 16).U.S. Coast Guard (reports from VHF 16). Life guard networks at area beaches.Life guard networks at area beaches. Local meso-scale analysis and forecast tools Local meso-scale analysis and forecast tools Well initialized local WRF runsWell initialized local WRF runs AWIPS LAPS data with quality controlled observational inputs.AWIPS LAPS data with quality controlled observational inputs.

25. Thermal, Moisture and Wind Profiles… Shallow, steeper low level lapse rate just above the surface. OR Light easterly tropical flow is conducive to organizing landbreeze convergent lines offshore OR no flow at all!

26. Convergent TCU Zones… Visible imagery shows location of convergent lines where TCu is growing. 88D reflectivity shows where the showers are organizing along the convergence lines.

27. NEXRAD shows where showers are forming along the TCu line… Strengthening updrafts along the remnant land breeze convergent zone Some studies have shown that intersecting boundaries will focus misocyclone formation (Wakimoto and Wilson, 1989).

28. SRM data won’t likely show the circulation… …the TCu and showers are forming on the boundary 40-55 nm from the radar site…and the circulation is probably not being sampled due to range and aspect ratio considerations. However, if the radar site is within 40 nm of the report or suspect area…Spectrum Width (SW) data may help!

29. Waterspout – 12 Oct 2009 – Mobile Bay

30. 1455 UTC

31. Waterspout – 12 Oct 2009 – Mobile Bay 1455 UTC

32. Waterspout – 12 Oct 2009 – Mobile Bay 1459 UTC

33. Waterspout – 12 Oct 2009 – Mobile Bay 1503 UTC

34. Waterspout – 12 Oct 2009 – Mobile Bay 1508 UTC

35. Radar Observation of the Misocyclone From Wakimoto and Wilson, 1988: From Wakimoto and Wilson, 1988: Radar vortex can precede visual vortex by 14 mins… but…Radar vortex can precede visual vortex by 14 mins… but… Vortices are shallow and small forming below 2 km… (dia <2 km)Vortices are shallow and small forming below 2 km… (dia <2 km) Average maximum horizontal shear=.062 s-1Average maximum horizontal shear=.062 s-1 Parent cloud is often Cu that evolve into CB at a later stageParent cloud is often Cu that evolve into CB at a later stage

36. 88D Strategy… High resolution radar reflectivity data can show boundaries better…a significant improvement. High resolution radar reflectivity data can show boundaries better…a significant improvement. 0.5 degree/0.25 km resolution versus 1 degree/1 km legacy.0.5 degree/0.25 km resolution versus 1 degree/1 km legacy. Sampling - Beam elevation and aspect ratio considerations will limit detection with SRM data. Weak circulations close to the radar may be evident…but not likely sampled adequately. Sampling - Beam elevation and aspect ratio considerations will limit detection with SRM data. Weak circulations close to the radar may be evident…but not likely sampled adequately. Spectrum Width (SW) can be useful in detection of suspect areas…if the suspect area is close enough to the radar. Spectrum Width (SW) can be useful in detection of suspect areas…if the suspect area is close enough to the radar.

37. Forecasters now have some powerful tools to better forecast and detect the coastal waterspout environment… AWIPS 5 km LAPS analysis of wind, convergence, instability, etc. Local higher 5 km resolution WRF model runs that give guidance on convergence zones, instability, and wind profiles.

38. Identifying Waterspout Days or... HWO 0-24 h 1-3 h

39. On Polygon Warnings for Waterspouts Tornado Warning for Land-falling waterspout… More on TOR vs. SMWs Golden has documented up to 85 m/s (or ~190 kt) in large FL Keys waterspouts! NWSI SMW and SVR Chapters for a TOR does not elaborate on exactly what action to take (very nebulous). For WFO MOB, we typically issue a SMW for a land-falling waterspout (i.e., a non- supercell tornado process), unless we have some evidence that it is very large and\or life-threatening because most of the time they dissipate immediately and winds are much less than 60 mph. FAR problem (especially public perception), and it usually dissipates right on the beach. By the time a warning would be issued, it would be gone!

40. We’ve progressed in the last 20 years with… Better understanding of the environment they form in… Better understanding of the environment they form in… Higher resolution radar data allowing for better identification of boundaries… Higher resolution radar data allowing for better identification of boundaries… Higher resolution satellite data… Higher resolution satellite data… Better educated spotters along the coast… Better educated spotters along the coast… Last but not least…our higher resolution mesoscale models (such as the local WRF and now HRRR) and other analysis tools (e.g., LAPS) have brought a plethora of new tools to the forecast desk. Last but not least…our higher resolution mesoscale models (such as the local WRF and now HRRR) and other analysis tools (e.g., LAPS) have brought a plethora of new tools to the forecast desk.

41. References Golden, J.H. (1971): “Tornadoes and Waterspouts over South Florida”, AMS Monthly Weather Review 99: 146-154 Golden, J.H. (1971): “Tornadoes and Waterspouts over South Florida”, AMS Monthly Weather Review 99: 146-154 Golden, J.H. (1977): “An Assessment of Waterspout Frequencies Along the U.S. East and Gulf Coasts”, AMS Journal of Applied Meteorology 16: 231-236 Golden, J.H. (1977): “An Assessment of Waterspout Frequencies Along the U.S. East and Gulf Coasts”, AMS Journal of Applied Meteorology 16: 231-236 Wakimoto, R.M., Wilson, J.W. (1989): “Non-Supercell Tornadoes” AMS Monthly Weather Review 117: 1113-1140 Wakimoto, R.M., Wilson, J.W. (1989): “Non-Supercell Tornadoes” AMS Monthly Weather Review 117: 1113-1140 Brady, R.H., Szoke, E.J. (1989): “A Case Study of Non- Mesocyclone Tornado Development in Northeast Colorado: Similarities to Waterspout Formation” AMS Monthly Weather Review 117: 843-856 Brady, R.H., Szoke, E.J. (1989): “A Case Study of Non- Mesocyclone Tornado Development in Northeast Colorado: Similarities to Waterspout Formation” AMS Monthly Weather Review 117: 843-856 Choy, LT(jg) B.K., Spratt, S.M. (1994): “A WSR-88D Approach to Waterspout Forecasting” NOAA Technical Memorandum NWS SR- 156 Choy, LT(jg) B.K., Spratt, S.M. (1994): “A WSR-88D Approach to Waterspout Forecasting” NOAA Technical Memorandum NWS SR- 156

42. References Burgess, D.W., Donaldson, R.J. Jr., Desrochers, P.R. (1993): “Tornado Detection and Warning by Radar” Geophysical Monograph 79: 203-221 Burgess, D.W., Donaldson, R.J. Jr., Desrochers, P.R. (1993): “Tornado Detection and Warning by Radar” Geophysical Monograph 79: 203-221 Caruso, J.M., and Davies, J.M., (2005): “Tornadoes in Non- mesocyclone Environments with Pre-existing Vertical Vorticity along Convergence Boundaries”: NWA Journal of Operational Meteorology. Caruso, J.M., and Davies, J.M., (2005): “Tornadoes in Non- mesocyclone Environments with Pre-existing Vertical Vorticity along Convergence Boundaries”: NWA Journal of Operational Meteorology. Fujita, T., (1981): “Tornadoes and downbursts in the context of generalized planetary scales.” AMS Journal of Atmospheric Science 38: 1511-1534. Fujita, T., (1981): “Tornadoes and downbursts in the context of generalized planetary scales.” AMS Journal of Atmospheric Science 38: 1511-1534.

43. Central Gulf Coast Waterspouts…