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

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

Presentation OutlinePresentation Outline

Briefly review 6 case studies illustrating Briefly review 6 case studies illustrating the short-term (0-12 hour) forecast utility the short-term (0-12 hour) forecast utility of the TAMDAR regional aircraft sounding of the TAMDAR regional aircraft sounding data.data.

All cases (except May, 21, 2005) were in or All cases (except May, 21, 2005) were in or near the Green Bay (GRB) forecast area.near the Green Bay (GRB) forecast area.

In all cases examined, all or a portion of In all cases examined, all or a portion of the forecast area was either included in a the forecast area was either included in a Day 1 Convective Outlook (Slight, Day 1 Convective Outlook (Slight, Moderate or High Risk area) and/or a Moderate or High Risk area) and/or a Watch (Severe or Tornado) was in effect. Watch (Severe or Tornado) was in effect.

Convective Case #1 - June 04 2005Convective 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.

Convective Case #1 June 04 2005Convective 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

Convective Case #1 Convective Case #1 June 04 2005June 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.


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.


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


At least 7 reports of very brief tornado touchdowns (most with minor or no damage).

Numerous additional funnel cloud reports.


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)


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.

Convective Case #2 Convective Case #2 June 07, 2005June 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.


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.


Soundings immediately downstream of the approaching MCS (MPX & EAU) indicated a rather dry air mass in the 900 to 700 mb layer.

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) .

Convective Case #2 June 07 2005Convective Case #2 June 07 2005

Comparison to 12Z GRB RAOB (right)


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.


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.


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.


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.

Convective Case #2 Convective Case #2 June 07 2005 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.


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.

Convective Case - #2 June 07 2005Convective 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).

Case #3 - June 13, 2005Case #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.


Storms evolved in rather benign synoptic setting with very weak wind fields and weak deep layer shear.

Note 12Z GRB sounding (below)

Case #3 June 13, 2005Case #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.


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.


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 APPEARS ENVIRONMENT 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.

Convective Case #4 Convective Case #4 July 24, 2005July 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.


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.

Case #4 July 24, 2005Case #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.


By 0100Z that evening, convective outlook downgraded from Moderate to Slight Risk.

Radar data indicated mainly light shower activity in the outlook area.

Case #4 July 24, Case #4 July 24, 20052005

Convective Case #4 July 24, 2005Convective Case #4 July 24, 2005

TAMDAR soundings across the region continued to show very impressive mid-level capping inversion during the evening.


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.


The morning after…The 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.

Convective Case #5 Convective Case #5 August 7, 2005August 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.

Case #5 Case #5 August 7, 2005August 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.

Convective Case #5 Convective Case #5 August 7, 2005August 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.

Case #5 August 7, 2005Case #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.

????


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.

One office decides to add chance of thunderstorms to forecast based on SPC outlook and model forecasts…


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.

Case #5 August 7, 2005Case #5 August 7, 2005MESOSCALE 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.


TAMDAR soundings continue to show very strong cap and very weak wind profile compared to 17Z RUC. Both soundings quite dry.

Case #5 Case #5 August 7, 2005August 7, 2005

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.

18Z RUC .vs. MSP TAMDAR sounding (left)

Cap more pronounced in MSP aircraft sounding compared to RUC.


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.


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.

Case # 6 – May 21 2005Case # 6 – May 21 2005

Courtesy of Phil Schumacher (SOO FSD) and Phil Kurimski (GRB)Courtesy of Phil Schumacher (SOO FSD) and Phil Kurimski (GRB)

TAMDAR was used by meteorologists at the TAMDAR was used by meteorologists at the NWS office in Sioux Falls, South Dakota NWS office in Sioux Falls, South Dakota during an during an expectedexpected convective event on convective event on May 21, 2005.May 21, 2005.

Model soundings suggested that a mid level Model soundings suggested that a mid level cap would erode during the late afternoon, cap would erode during the late afternoon, resulting in strong or severe thunderstorms.resulting in strong or severe thunderstorms.

The Storm Prediction Center (SPC) had this The Storm Prediction Center (SPC) had this area in a Convective Outlook, and later area in a Convective Outlook, and later issued a Tornado Watch. issued a Tornado Watch.

Case # 6 - Background InformationCase # 6 - Background Information

Sioux Falls forecasters looked at TAMDAR Sioux Falls forecasters looked at TAMDAR soundings from Sioux City, Iowa during the late soundings from Sioux City, Iowa during the late afternoon and early evening hours.afternoon and early evening hours.

The soundings showed a mid level cap that would The soundings showed a mid level cap that would be nearly impossible to overcome by expected be nearly impossible to overcome by expected surface heating. Therefore, they lowered the surface heating. Therefore, they lowered the probability of thunderstorms in their local probability of thunderstorms in their local forecasts. forecasts.

Based upon the observation that the cap would Based upon the observation that the cap would be too strong to overcome, they coordinated with be too strong to overcome, they coordinated with SPC to leave six of their counties out of the SPC to leave six of their counties out of the tornado watch. No severe weather occurred in tornado watch. No severe weather occurred in those counties. those counties.

Sioux Falls Forecast AreaSioux Falls Forecast Area

The Sioux Falls NWS is responsible for severe weather warnings for these counties

Surface Map 12ZSurface Map 12Z 5/21/20055/21/2005A surface low was moving east towards Minnesota. The easternDakotas, westernMinnesota, easternNebraska and western Iowa were forecast to be in thewarm sector in thelate afternoon.

12Z Model forecastsoundings suggestedmid level cap wouldbe overcome in thelate afternoon, withCapes of 2-3,000 J/kgand significant shear

SPC Day 1 OutlookSPC Day 1 Outlook

SPC correctly identified the SPC correctly identified the significant cap over the Plains states significant cap over the Plains states in this 1630UTC update.in this 1630UTC update.

Models forecast cap to be overcome Models forecast cap to be overcome by strong surface heating and mid by strong surface heating and mid level cooling in the late afternoon.level cooling in the late afternoon.

CAPE and shear profiles from models CAPE and shear profiles from models suggested that thunderstorms that suggested that thunderstorms that resulted could be severe. resulted could be severe.

SPC Day 1 OutlookSPC Day 1 Outlook

DAY 1 CONVECTIVE OUTLOOKNWS STORM PREDICTION CENTER NORMAN OK1120 AM CDT SAT MAY 21 2005 VALID 211630Z - 221200Z...NE/IA/KS/MO... MORNING SOUNDINGS CONFIRM THAT A SUBSTANTIAL CAP CURRENTLY ACROSSTHE PLAINS ASELEVATED MIX LAYER HAS SPREAD EWD OVERNIGHT WITH VERYSTEEP MID LEVEL LAPSE RATES. 50KT LOW LEVEL JET AHEAD OF COLD FRONTWILL RAPIDLY INCREASE LOW LEVEL MOISTURE NWD THRU CENTRAL PLAINSTHIS AFTERNOON. WHILE NAM SEEMS A LITTLE AGGRESSIVE ON MOISTURETRANSPORT...GIVEN THE OBSERVED DEWPOINTS RISING THRU THE 60S FACROSS CENTRAL KS...SUBSTANTIALDESTABILIZATION IS EXPECTED AHEAD OFCOLD FRONT BY MID/LATE AFTN AS FAR N AS ERN NEB/WRN IA. EROSION OF THE EXISTING STRONG CAP WILL TAKE PLACE THIS AFTERNOONTHRU STRONG SURFACE HEATING AND LARGE SCALE VERTICAL MOTION AHEAD OFFRONT AND APPROACHINGUPPER TROUGH. BY LATE AFTERNOON WITH MLCAPES BETWEEN 2000-3000 J/KG COUPLED…

Radar and satellite data at 18ZRadar and satellite data at 18Z

18Z radar from Omaha showed scattered 18Z radar from Omaha showed scattered showers over northern and central Iowa.showers over northern and central Iowa.

An 18Z satellite picture showed clear An 18Z satellite picture showed clear skies over western Iowa and the eastern skies over western Iowa and the eastern Dakotas, except for developing cumulus.Dakotas, except for developing cumulus.

These cumulus were expected to develop These cumulus were expected to develop into thunderstorms as the cap was into thunderstorms as the cap was broken. broken.

Radar from Omaha at 18ZRadar from Omaha at 18Z

Radar shows scattered showers over northern and central Iowa at 1800Z. Eastern Nebraska and Southwest Iowa arecurrently free of echoes.

Visible satellite picture at 18ZVisible satellite picture at 18Z

Visible satellite picturefrom 18Z shows somecumulus clouds forming over the easternDakotas, easternNebraska and westernIowa.

These clouds will laterhave little verticalextent due to the mid level capping inversion

A Waiting Game…A Waiting Game…

Now NWS WFOs in the outlook area Now NWS WFOs in the outlook area must wait and see whether mid level must wait and see whether mid level cap over the Iowa, Minnesota and cap over the Iowa, Minnesota and eastern Nebraska can be broken. eastern Nebraska can be broken.

Until recently, forecasters had no real Until recently, forecasters had no real time way of assessing cap strengthtime way of assessing cap strength

TAMDAR and MDCRS data are now TAMDAR and MDCRS data are now available, and can help meteorologists available, and can help meteorologists determine convective potential in real determine convective potential in real time.time.

12Z NAM Soundings from SUX12Z NAM Soundings from SUX

The 20Z sounding shows a cap similar to the TAMDAR sounding. The cap was forecast to break by 23Z as shown on the right.

23Z SUX TAMDAR Sounding23Z SUX TAMDAR Sounding

The cap did not break by 23Z as forecast by the NAM. A TAMDAR sounding from that same time shows the inversion was still in place and fairly strong.

ResultsResults

Forecasters at the Sioux Falls office viewed Forecasters at the Sioux Falls office viewed the TAMDAR data in the NSHARP program the TAMDAR data in the NSHARP program to further refine the convective potential.to further refine the convective potential.

They determined that the cap would not They determined that the cap would not likely be overcome, despite model likely be overcome, despite model forecasts suggesting it would. forecasts suggesting it would. Therefore, Therefore, they lowered the probability of they lowered the probability of thunderstorms in their local forecasts.thunderstorms in their local forecasts.

They also They also coordinated with SPC to leave coordinated with SPC to leave six of their counties out of a tornado watch six of their counties out of a tornado watch that was issued. that was issued.

Tornado Watch IssuedTornado Watch Issued

The Sioux Falls NWSasked the Storm Prediction Center toleave six counties of their forecast area out of a Tornado Watch that was issued during the late afternoon. The SPC agreed, and no severeweather occurred in those counties.

Preliminary severe weather reports Preliminary severe weather reports May 21, 2005May 21, 2005

The lack of severe weather reports from the tornado watch area shows that the mid level inversion was indeed too strong to get severe weather.

Impacts of Convective Watches and Outlooks…Impacts of Convective Watches and Outlooks…

Update hazardous outlook (alerts emergency managers and Update hazardous outlook (alerts emergency managers and storm spotters for potential for severe weather)storm spotters for potential for severe weather)

Consideration of available staffing to cover NWS warning Consideration of available staffing to cover NWS warning operations. Staff held over for OT during Watch.operations. Staff held over for OT during Watch.

Update forecast/NDFD grids, NSH, etc.Update forecast/NDFD grids, NSH, etc. Potential Media HypePotential Media Hype Aviation (include thunder in TAFS)…more fuel costs.Aviation (include thunder in TAFS)…more fuel costs. General public (recreational/boaters/campers, etc., change plans) General public (recreational/boaters/campers, etc., change plans)

Bottom LineBottom Line …The increased temporal and spatial …The increased temporal and spatial resolution regional aircraft sounding data holds resolution regional aircraft sounding data holds significant potential in assisting forecasters in significant potential in assisting forecasters in better assessing short-term convective potential better assessing short-term convective potential and refining convective outlooks and watches and refining convective outlooks and watches (greatest threat areas). (greatest threat areas).

AcknowledgementsAcknowledgements Rich Mamrosh (WFO GRB) – Review of this presentation and Rich Mamrosh (WFO GRB) – Review of this presentation and

helpful comments.helpful comments.

Phil Schumacher (WFO FSD) & Phil Kurimski (WFO GRB) – Phil Schumacher (WFO FSD) & Phil Kurimski (WFO GRB) – Preparation of May 21, 2005 example.Preparation of May 21, 2005 example.

Bill Moninger (NOAA, FSL) – Assistance with FSL Aircraft Java Bill Moninger (NOAA, FSL) – Assistance with FSL Aircraft Java web page.web page.

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

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