Utility of Regional TAMDAR Sounding Data In Short-Term Convective Forecasting

1. Utility of Regional TAMDAR Sounding Data In Short-Term Convective Forecasting Gene Brusky Science and Training Meteorologist National Weather Service Green Bay, Wisconsin TAMDAR GLFE Status Meeting August 24-25 FSL, Boulder, CO

2. Presentation Outline • Briefly review 6 case studies illustrating the short-term (0-12 hour) forecast utility of the TAMDAR regional aircraft sounding data. • All cases (except May, 21, 2005) were in or near the Green Bay (GRB) forecast area. • In all cases examined, all or a portion of the forecast area was either included in a Day 1 Convective Outlook (Slight, Moderate or High Risk area) and/or a Watch (Severe or Tornado) was in effect.

3. Convective Case #1 - June 04 2005 Visible Satellite Loop 21Z – 23Z June 04, 2005 Warm front moving northeast into central Wisconsin Overall instability over the forecast area expected to be marginal initially due to extensive cloud cover. Atmosphere was expected to quickly destabilize further to the southwest (Iowa, SE Minnesota into SW WI) during the afternoon as the warm front pushed northeast.

4. Convective Case #1 June 04 2005 12Z RAOB soundings suggest marginal instability and weak deep layer shear. Initially atmosphere did not appear very supportive for strong-severe thunderstorms in the Green Bay (GRB) forecast area. However…1428Z CWA TAMDAR sounding (located between MSP and GRB) indicated more veering and stronger mid-level winds

5. Convective Case #1 June 04 2005 Deep layer wind shear was expected to become more favorable to support severe thunderstorms later in the day mainly over Iowa, southern Minnesota and southwest Wisconsin.

6. Convective Case #1 - June 04 2005 Radar Loop 1918Z – 2121Z June 04, 2005 Early in the day, forecasters were anticipating scattered thunderstorms during the afternoon with marginal severe potential (hail and damaging straight-line winds) mainly over the southwest portion of Wisconsin. Scattered thunderstorms did break out along and north of the warm front during the afternoon. A few of the storms produced numerous funnel clouds and weak (F0) tornadoes which caught GRB forecasters somewhat by surprise.

7. Convective Case #1 June 04 2005 Storms were generally small, low-topped and not very well organized. Radar detected generally weak, transient circulations. Storms in Marathon County (above) were at far ranges from the radar making it difficult to assess storm structure and circulations. The radar signatures in this example were probably the most impressive of the day

8. Convective Case #1 June 04 2005 At least 7 reports of very brief tornado touchdowns (most with minor or no damage). Numerous additional funnel cloud reports.

9. Convective Case #1 - June 04 2005 SPC hourly mesoanalysis graphics 18Z & 21Z 0-3 km Cape (top) 0-1 km SRH (bottom) SPC analysis indicated that the environment (particularly at low-levels) was rapidly becoming more favorable for tornadoes along and just north of the approaching warm front. TAMDAR soundings are a useful supplement to the SPC mesoanalysis graphics. Threat area (blue box)

10. Convective Case #1 June 04 2005 CWA TAMDAR soundings indicated environment in vicinity of the warm front was becoming more supportive of tornadoes. Low-level wind shear was increasing, low-level CAPE was substantial and LCL heights were quite low. Note difference between 1428Z and 1943Z CWA TAMDAR sounding. Regional soundings allow forecasters to better monitor rapidly changing environments and better anticipate tornado potential. Forecaster can react more quickly after first funnel cloud report and possibly issue tornado warning sooner.

11. Convective Case #2 June 07, 2005 Damaging wind-producing linear MCS developed overnight over western Minnesota north of an advancing warm front. By 15Z June 07, 2005, the storms were rapidly approaching the Green Bay (GRB) forecast area.

12. Convective Case #2 June 07 2005 Although the storms had weakened slightly during the morning hours, there was concern that the MCS would re-intensify as it moved east into central Wisconsin. RUC soundings suggested that the atmosphere ahead of the MCS would destabilize sufficiently to support surface-based convection and maintain the convective system. SPC coordination call was initiated with affected WFOs around 15Z and a Severe Thunderstorm Watch was issued downstream from the MCS.

13. Convective Case #2 June 07 2005 Soundings immediately downstream of the approaching MCS (MPX & EAU) indicated a rather dry air mass in the 900 to 700 mb layer.

14. Downstream of the MCS later that morning, aircraft soundings (CWA & ATW) continued to indicate a rather dry air mass and substantial capping inversion. Supplemental regional TAMDAR soundings suggested deep dry layer would help erode precipitation and new surface-based convection would be unlikely (given increasingly overcast conditions) .

15. Convective Case #2 June 07 2005 Comparison to 12Z GRB RAOB (right)

16. Convective Case #2 - June 07 2005 By early afternoon, the MCS almost completely dissipated except for some widely scattered convection near the thunderstorm outflow. No severe weather occurred anywhere in the Green Bay (GRB) forecast area. Watch was eventually cancelled.

17. Convective Case #2 June 07 2005 Capping inversion strengthen as MCS moved across central Wisconsin and dissipated (right). 19Z RUC did not appear to capture strength of capping inversion. Despite low-level stable layer…deep layer shear was gradually increasing during the afternoon.

18. Convective Case #2 June 07 2005 In the wake of the MCS…where skies cleared…the atmosphere was expected to destabilize rapidly later in the afternoon as insolation continued. This in concert with lift ahead of approaching shortwave would help erode the capping inversion.

19. Convective Case #2 June 07 2005 Regional TAMDAR soundings not only helped forecasters diagnose the strength of the capping inversion early in the day…but also helped monitor the subsequent rapid erosion of the capping inversion as skies cleared ahead of approaching upper-air disturbance and cold front. Note the difference between the 1923Z and 2336Z CWA soundings. During the afternoon, drier air mixed downward which increased LCL heights.

20. Convective Case #2 June 07 2005 Severe convection rapidly developed between 20z and 22Z ahead of cold front over western Wisconsin and over northern Wisconsin along east-west boundary. Two Tornado Watch boxes issued.

21. Convective Case #2 June 07 2005 Several well-organized supercell thunderstorms developed with moderate to strong rotation prompting the issuance of several tornado warnings in the GRB forecast area. Despite several reports of large hail and some straight line wind damage…no tornados were confirmed during the event in the Green Bay (GRB) forecast area.

22. Convective Case - #2 June 07 2005 CWA TAMDAR soundings (above) suggest that LCL/LFC heights may have been too high (given the magnitude of the wind shear) to support supercell tornado development. Compare to previous June 4 case (left). Regional TAMDAR show some utility in evaluating LCL/LFC heights with respect to tornado potential (ala Jon Davies recent research).

23. Case #3 - June 13, 2005 Band of showers and thunderstorms moving northeast well ahead of warm front. Most of Green Bay (GRB) forecast area in general thunder and not included in risk of severe thunderstorms next 12 hours. However…by early afternoon GRB office receives several funnel cloud reports and brief tornado touchdowns/ waterspouts on Lake Winnebago.

24. Case #3 - June 13, 2005 Storms evolved in rather benign synoptic setting with very weak wind fields and weak deep layer shear. Note 12Z GRB sounding (below)

25. Case #3 June 13, 2005 Despite weak deep layer shear, the atmosphere by early afternoon was becoming very unstable as temperatures climbed into the middle 80s with surface dew points near 70 degrees F.

26. Case #3 - June 13, 2005 Monitoring of Appleton (ATW) TAMDAR soundings throughout the morning indicated steeping low-level lapse rates leading to large values of 0-3 km CAPE. Large values of low-level (0-3 km) CAPE and low LCL/LFC heights in presence of boundary interactions (e.g., numerous lake breeze/thunderstorm outflow boundary interactions on this day) increased the tornado potential. TAMDAR soundings helped forecasters better anticipate the rather subtle, weak tornado/waterspout potential and relay that information to the public.

27. Case #3 - June 13, 2005 AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREEN BAY WI 330 PM CDT MON JUN 13 2005 SHORT-TERM UPDATE... NW-SE ORIENTATED LINE OF MARGINALLY SEVERE THUNDERSTORMS MOVING ACROSS THE CENTRAL AND EAST-CENTRAL PORTION OF THE FORECAST AREA. ALTHOUGH OVERALL INSTABILITY SUFFICIENT...DEEP LAYER SHEAR STILL SOMEWHAT MARGINAL TO SUSTAIN ORGANIZED/SUPERCELLULAR CONVECTION...THUS STORMS MORE MULTI-CELL/PULSE IN NATURE ATTM. HOWEVER...DESPITE WEAK DEEP LAYER SHEAR...18Z GRB AND 1735Z ATW TAMDAR AIRCRAFT SOUNDINGS INDICATE STEEP LOW-LEVEL LAPSE RATES AND SUBSTANTIAL LOW-LEVEL CAPE. THIS ENVIRONMENT... IN CONCERT WITH BOUNDARY INTERACTIONS ASSOCIATED WITH WARM FRONT AND LAKE-INDUCED BOUNDARIES...CAUSING FEW STORMS TO GENERATE VERY BRIEF WEAK SPIN-UPS...WITH A PUBLIC AND LAW ENFORCEMENT REPORT OF A TORNADO NEAR NEW LONDON. IT APPEARSENVIRONMENT WILL CONTINUE TO BE FAVORABLE FOR A FEW GENERALLY WEAK BRIEF SPIN-UPS NEXT HOUR OR SO... ESPECIALLY NEAR BOUNDARIES. DEEP LAYER SHEAR TO STRENGTHEN OVER FAR WESTERN PORTION OF THE FORECAST AREA LATER THIS EVENING AS UPPER-JET MAX OF 60 KNOTS APPROACHES SOUTHWEST WISCONSIN...THUS ANTICIPATE MORE ORGANIZED SEVERE CONVECTION LATER THIS EVENING AFTER INITIAL MULTICELL CONVECTION THIS AFTERNOON.

28. Convective Case #4 July 24, 2005 Large damaging wind-producing MCS moves across central and southeast Wisconsin during the afternoon hours of July 24, 2005. Widespread wind damage reported across eastern Minnesota, western and central Wisconsin.

29. Convective Case #4 July 24, 2005 Around 20Z…in the wake of the departing MCS…convective outlook highlights moderate risk for severe convection later in the evening from central Wisconsin to western Minnesota. Low-level jet forecast to intensify over the region overnight as upper-level disturbance approaches from the west later on.

30. Case #4 July 24, 2005 Although TAMDAR soundings (from 17Z to 23Z) located in the wake of the MCS reveal rather favorable vertical wind shear profiles to support severe convection and rather deep low-level moisture (ARX sounding)…mid-levels are very dry and strongly capped.

31. Convective Case #4 July 24, 2005 By 0100Z that evening, convective outlook downgraded from Moderate to Slight Risk. Radar data indicated mainly light shower activity in the outlook area.

32. Case #4 July 24, 2005 Convective Case #4 July 24, 2005 TAMDAR soundings across the region continued to show very impressive mid-level capping inversion during the evening.

33. Case #4 July 24, 2005 Around midnight…Slight Risk area removed from western Great Lakes region. Strong convection eventually develops further north near northern edge of the capping inversion. Mainly scattered marginal severe weather was reported during the overnight hours.

34. Case #4 July 24, 2005The morning after… A few scattered thunderstorms eventually develop in region of warm air advection ahead of weakening cold front over western Wisconsin by 8 am CDT the next day. GRB forecasters consider updating forecast with mention of thunderstorms… A look at the 13Z CWA TAMDAR sounding downstream of the convection indicates more of the same…too dry…too capped. Forecasters decide to keep forecast dry...and convection dissipates an hour later.

35. Convective Case #5 August 7, 2005 Elevated convection trying to develop along weak cold front and ahead of approaching upper-level disturbance over central Minnesota around mid-day August 7, 2005. Current forecast is dry over the entire western Great Lakes region for next 6-12 hours.

36. Case #5 August 7, 2005 All 12Z models (except GFS) forecast convection to develop by mid-day…then spread southeast into northwest Wisconsin by evening. Area has been under prolonged drought conditions and models (especially NAM) have been over forecasting boundary layer moisture and QPF in the region.

37. Convective Case #5 August 7, 2005 Comparison of 12Z model soundings to TAMDAR sounding near BRD suggest NAM too moist and does not capture magnitude of warm layer. GFS does capture capping inversion better than NAM.

38. Case #5 August 7, 2005 Day 1 convective outlook issued at 15Z has slight risk for severe over southern Minnesota into west-central Wisconsin. ???? Current forecast is dry. Short-term forecasters must now decide whether to update the forecast to include mention of thunder for this afternoon. ????

39. Case #5 August 7, 2005 One office decides to add chance of thunderstorms to forecast based on SPC outlook and model forecasts… AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE OFFICE 955 AM CDT SUN AUG 7 2005 . UPDATE...SURFACE STATIONARY FRONT CURRENTLY EXTENDS FROM SOUTHERN ONTARIO TO A WEAK LOW VICINITY OF KABR SD. MODELS INDICATE THE FRONT DIPPING SOUTH SOMEWHAT BY THIS AFTERNOON INTO NORTHWEST WI. MEANWHILE...CURRENT WATER VAPOR SATELLITE IMAGERY SHOWING A WEAK SHORTWAVE TROUGH MOVING EAST ACROSS EASTERN MT AT THIS TIME. THIS SHOULD LEAD TO SURFACE CYCLOGENESIS OVER THE DAKOTAS BY THIS AFTERNOON. THIS IN TURN SHOULD INCREASE MOISTURE TRANSPORT AHEAD OF IT INTO THE FRONT ACROSS NORTHWEST WI. NAM SHOWING FAIRLY GOOD ISENTROPIC LIFT ON THE 310K SURFACE MAINLY NORTH OF THE FORECAST AREA BY 21Z TO INITIATE CONVECTION ALONG THE FRONT. 12Z NAM ALSO SHOWING FAVORABLE 0-3KM SHEAR AROUND 20KT FOR PERHAPS A FEW THUNDERSTORMS WITH DAMAGING WINDS (PER SLIGHT RISK SPC DAY 1 OUTLOOK)...BUT AGAIN...THIS LOOKS TO BE NORTH OF THE FORECAST AREA.WILL BE UPDATING THE FORECAST TO INCLUDE A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS LATE THIS AFTERNOON.

40. Case #5 August 7, 2005 Comparison of 15Z RUC/NAM forecast to BRD TAMDAR sounding indicate atmosphere quite dry and cap much stronger than models. Also, BRD wind profile weaker than models…suggesting little support for strong updrafts. Forecaster decides to keep forecast dry for this afternoon…based primarily on TAMDAR sounding information and ongoing drought conditions.

41. Case #5 August 7, 2005 MESOSCALE DISCUSSION 1937 NWS STORM PREDICTION CENTER NORMAN OK 0142 PM CDT SUN AUG 07 2005 AREAS AFFECTED...N-CENTRAL MN AND NWRN WI CONCERNING...SEVERE THUNDERSTORM POTENTIAL VALID 071842Z - 072045Z ISOLATED SEVERE THUNDERSTORM DEVELOPMENT IS EXPECTED DURING THE NEXT 1-2 HOURS FROM N-CENTRAL MN EWD INTO FAR NWRN WI. LARGE HAIL IS LIKELY THE PRIMARY SEVERE THREAT...WITH LOCALIZED DAMAGING WINDS ALSO POSSIBLE. REGION IS BEING MONITORED FOR POSSIBLE WW. AT 1830Z...STATIONARY SURFACE FRONT EXTENDS NEWD FROM JUST SOUTH OF ABR TO 25S BRD TO THE NWRN SHORE OF LAKE SUPERIOR...WHERE IT MERGES WITH THE LAKE BREEZE. LOW-LEVEL MOISTURE ADVECTION COMBINED WITH EVAPOTRANSITIVE EFFECTS HAVE GRADUALLY MOISTENED BOUNDARY LAYER NEAR FRONT...WITH DEWPOINTS NOW IN THE LOW 70S ACROSS THE W-CENTRAL MN PORTION OF THE BOUNDARY. RUC BASED OBJECTIVE ANALYSIS FIELDS INDICATE THAT MLCIN REMAINS AROUND -100 J/KG NEAR THE FRONT...HOWEVER...WEAK ELEVATED STORMS EXIST ACROSS CROW WING AND CASS COUNTIES IN MN ASSOCIATED WITH MODEST LOW-LEVEL WARM ADVECTION THROUGH THE FRONTAL ZONE FROM THE SW. CONTINUATION OF WAA AND INCREASING MOISTURE SHOULD RESULT IN A GRADUAL INCREASE IN ELEVATED STORM ACTIVITY THROUGH MID-AFTERNOON.RUC SOUNDINGS INDICATE THAT MUCAPE VALUES AROUND BRD INCREASE TO 3500 J/KG BY 20Z ASSOCIATED WITH BOTH MOISTURE ADVECTION AND DIURNAL HEATING. EFFECTIVE SHEAR OF 25-30KT WILL SUPPORT A FEW LONG-LIVED CELLS WITH LARGE HAIL THE PRIMARY THREAT. CONVECTIVE TRENDS WILL BE CLOSELY MONITORED FOR A POSSIBLE WW IN THIS AREA DURING THE NEXT FEW HOURS...ESPECIALLY IF STORMS ARE EVENTUALLY ABLE TO BECOME SURFACE-BASED WITH CONTINUED SURFACE HEATING/LESSENING OF CIN THIS AFTERNOON. Later in the day…based partially on RUC soundings…region continues to be monitored for possible severe thunderstorm watch next few hours…especially if convection can become surface-based.

42. Case #5 August 7, 2005 TAMDAR soundings continue to show very strong cap and very weak wind profile compared to 17Z RUC. Both soundings quite dry.

43. Case #5 August 7, 2005 18Z RUC .vs. MSP TAMDAR sounding (left) Cap more pronounced in MSP aircraft sounding compared to RUC. Further to the east…18Z NAM run appears to have better handle on cap and moisture but still not as dry as RHI TAMDAR sounding indicates.

44. Case #5 August 7, 2005 AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREEN BAY WI 355 PM CDT SUN AUG 7 2005 . SHORT TERM...TONIGHT THROUGH MONDAY. OVERALL..LITTLE CHANGE TO PREVIOUS FORECAST IN THE SHORT-TERM. VIS SAT IMAGERY SHOWS MOSTLY CLEAR SKIES OF WESTERN GREAT LAKES. EXCEPTION IS SMALL AREA MID-LVL CLDS TRYING TO BECOME CONVECTIVE OVER LAST FEW HOURS IN CENTRAL MN. CLDS TRYING TO GET ORGANIZED IN AREA OF WAA ALONG AND JUST NORTH OF WEAK SFC BOUNDARY EXTENDING EAST-WEST ACROSS MN. OBSERVED REGIONAL AIRCRAFT SNDGS NEAR MSP...BRD...RHI...CONTINUE TO SHOW PERSISTENT MID-LEVEL DRY AIR AND CAP WHICH IS KEEPING ANY ORGANIZED CONVECTIVE DEVELOPMENT AT BAY. FCST NAM SNDGS TOO MOIST AND ONCE AGAIN OVERDOING QPF NEAR WEAK FRONTAL BOUNDARY FROM NE MN TO NW WI THIS EVENING. GFS FCST SNDGS/QPF MORE REALISTIC. SW APPOACHING MN FROM THE DAKOTAS THIS EVENING AND INCREASING WAA ASSOCIATED WITH 850 LLJ MAY HELP GET SCATTERED ELEVATED CONVECTION GOING THIS EVENING...HOWEVER LLJ APPEARS TO BE ADVECTING RATHER DRY AIR INTO NW WI OVERNIGHT. IF ANY PRECIP DEVELOPS OVERNIGHT WILL LIKELY BE QUITE ELEVATED...SCATTERED AT BEST AND SHOULD STAY WEST OF FCST AREA OVERNIGHT. THUS CONTNIUED DRY FCST THROUGH MIDDAY MONDAY. AS WEAK SFC FRONT SAGS INTO NW WI BY LATE MONDAY AFT...ADDED SLGT CHC POPS FOR FAR NW...BUT CONFIDENCE LOW.

45. Case #5 August 7, 2005 A few scattered elevated thunderstorms eventually try to get going in central Minnesota around 23Z (6 pm). Severe Thunderstorm Watch issued. Thunderstorms dissipate a few hours later and the Severe Thunderstorm Watch is cancelled.

46. Case # 6 – May 21 2005Courtesy of Phil Schumacher (SOO FSD) and Phil Kurimski (GRB) • TAMDAR was used by meteorologists at the NWS office in Sioux Falls, South Dakota during an expected convective event on May 21, 2005. • Model soundings suggested that a mid level cap would erode during the late afternoon, resulting in strong or severe thunderstorms. • The Storm Prediction Center (SPC) had this area in a Convective Outlook, and later issued a Tornado Watch.

47. Case # 6 - Background Information • Sioux Falls forecasters looked at TAMDAR soundings from Sioux City, Iowa during the late afternoon and early evening hours. • The soundings showed a mid level cap that would be nearly impossible to overcome by expected surface heating. Therefore, they lowered the probability of thunderstorms in their local forecasts. • Based upon the observation that the cap would be too strong to overcome, they coordinated with SPC to leave six of their counties out of the tornado watch.  No severe weather occurred in those counties.

48. Sioux Falls Forecast Area The Sioux Falls NWS is responsible for severe weather warnings for these counties

49. Surface Map 12Z5/21/2005 A surface low was moving east towards Minnesota. The eastern Dakotas, western Minnesota, eastern Nebraska and western Iowa were forecast to be in the warm sector in the late afternoon. 12Z Model forecast soundings suggested mid level cap would be overcome in the late afternoon, with Capes of 2-3,000 J/kg and significant shear

50. SPC Day 1 Outlook • SPC correctly identified the significant cap over the Plains states in this 1630UTC update. • Models forecast cap to be overcome by strong surface heating and mid level cooling in the late afternoon. • CAPE and shear profiles from models suggested that thunderstorms that resulted could be severe.