ProbWind Underdone and Missed a Warning

Here is a 50 minute loop of 0.5 Velocity data from BGM.  Notice the strong area of winds approaching the radar.  It's around 50 kt a few thousand feet off the surface.  The second image measures 52 kt at 2,500 feet AGL.  But ProbWind reported 1% probability for virtually the entire time.  This is massively underdone.  Why?  50 kt is Severe Thunderstorm Warning criteria.  If this wind a few thousand feet above ground mixes down to the surface, then it's easily SVR criteria.  Yet the ProbWind is only 1%.

So what happened?  At 1927Z (image three) NWS BGM reported tree limbs and wires down on Timberline Drive.  This matches up fairly well with the general location highlighted in image two.  If forecasters were relying solely on ProbWind, they would have missed a warning.  It needs to factor the SRM and Velocity data into the calculations.  Otherwise, forecasters may not be as confident in the ProbWind data.

 

-Kevin

PW's/Instability Increasing across DMX (Des Moines, IA)

AllSkyLAP PW product indicates moistening in the low and mid levels across DMX FA this afternoon (Figure 1). AllSkyLAP Instability parameters are also on the rise (Figure 2).

Figure 1. AllSkyLAP PW product. Top Left: SFC-900mb; Top Right: 900mb-700mb; Bottom Right: Layer PW; Bottom Left 700mb-300mb

Figure 2. AllSkyLAP products. Top Left: Layer CAPE; Top Right: Layer LI; Bottom Right: Layer Cloud Type; Blue=Clear Skies; Gray=GFS First Guess; Yellow=Cloudy Skies

- BO

BGM initial thoughts

A more subtle severe weather threat is expected relative to the past couple of days. Convection to the west is spreading east into the BGM area at the start of operations. Overall instability is weak with observed and SPC analysis CAPE ~500-1000 J/kg at best. Shear is strong and storm motions may be on the order of 50kt owing to a severe wind threat. The southern half of the BGM area seems most at risk for severe weather with better instability south of a boundary slowly sinking south with time.

ProbSevere Provides Valuable Lead Time for ICT

ProbSevere provided valuable lead time on redevelopment of MCS in northern portions of ICT CWA after 6:00pm local time. Quarter size hail was reported in Madison County (two counties NNE of radar) at 6:15pm, where ProbHail increased to over 80% (Figure 1). ProbWind remained rather high through the event (>80%), so was less useful, but became maximized as the storm moved through Chase and Greenwood counties, where wind gusts of 65-70 mph were reported.

Figure 1. ProbHail spiked back up on storm over central Marion County (two counties NNE of Radar) between 6:00pm and 6:15pm when quarter size hail 

was reported.

Figure 2. ProbWind proved less usefull as values remained quite high 

throughout event, but severe wind gusts were reported in Chase and northern

Greenwood counties. 

- BO

Week 1 Day 4 Operations

For today we will be beginning operations in the Des Moines, IA and Bighampton, NY CWAs.

Michael

Week 1 Day 3 Wrap Up and Feedback

We had another busy day yesterday with a tornado warning over us during operations! Feedback from the day is posted below:

ABI and All-Sky LAP

CAPE as usual seemed to be lower than it should
Where there was clear air it seemed to get a good retrieval but the area where the GFS retrieval is
taking over is scattered and pixely

Shows a blank screen every hour on the hour when there is no retrieval

DMWs analyzed the jet well with the diffluence aloft where the convection was firing

Could see the lower level winds start to back as the evening wore on just as surface winds started to
back

Can’t really use the day cloud phase for monitoring storm top features since the Vis gets washed out

Getting RGB application labels built into AWIPS would be nice to mouse over for labeling of what is
represented in the RGB similar to the radar Hydrometeor classification.

Would prefer to see the actual readout from the channels on RGB instead of a number from 0-255

CI

Probabilities ramped up all over the place really but wasn’t specific to the location

Seemed overly sensitive and jumped around a lot

Wasn’t used a lot due to a couple of known issues being worked

NUCAPS

A fix was put in that every green point will at least have a surface moderation if the rest of the algorithm
doesn’t modify the profile

Gridded product hasn’t gotten much use due to a large number of clouds in the area throughout the day

Compared the profiles to the special Norman sounding and it didn’t pick up the inversion or the EML as
well as what was present

700mb temps seemed to match pretty well compared to RAP analysis to monitor CAP strength across
the area

ProbSevere

Preference for the all hazards and for ProbTor to be on the same display

ProbWind seemed to be high (80 - 90%) across much of the time when the line was sub severe

Some kind of velocity information would be useful for wind information

Probabilities lagged slightly behind the base data analysis for a couple of storms in Kansas

Might be useful to highlight areas of maximum Az shear in line segments after reaching a certain
thresholds based on distance from radar

As storms were splitting the contour would highlight both storms and cause confidence to be lost for
those splitting storms

GLM

It was difficult to determine which lightning cores correlated to which storms in the radar

It would be better to have a cumulative 5 minute product that updates every minute to better see trends
and relate to the stronger cores

It was helpful to have the flash area and flash energy to help pick out the storms different behavior and
distinguish the stronger updrafts from weaker updrafts

It would be most useful to be able to get these products into one product to be able to be used by a
forecaster

Having useful examples for training will be helpful

Michael

GLM Loop

Here is a 30-minute loop of GLM data.
Top Left is Flash Extent Density
Top Right as Average Flash Area
Bottom Right is Total Energy
Bottom Left is 0.5 Reflectivity

Notice the increase in lightning around the perimeter at 00:18Z.  This is probably anvil lightning being detected across the entire line.

-Kevin

God help us...he's trying to issue warnings!

Had fun pretending to issue warnings today.  Was monitoring a cell that had a persistent, not super impressive mid level rotation.  Suddenly the cell developed a very strong low level rotation on the 0.5 tilt of the FDR radar.  I definitely wasn't expecting to see something develop such a strong signal that would immediately make me think of issuing a TOR.  I easily could have been paying attention to some other cells.

At the time that the low level circulation became visibly obvious to me, ProbSevere had 17% for TOR (values above 80% for wind/hail like most storms today).  In one or two updates it jumped to 72%.  ProbSevere showed potential to draw my attention back to the cell very shortly after development had I been looking elsewhere.

(FDR radar SRM loop)

-Forrest

SNPP NUCAPS Near Norman

SNPP NUCAPS valid shortly after 1910 UTC was available in AWUPS around 2000 UTC, providing an opportunity to compare with the 1800 UTC Norman radiosonde. Jack adjusted the "Modified NUCAPS" code to allow for surface modifications (using RTMA) still even when the more intensive modification cannot be made. This worked, and prevents the user from having to modify the the surface. The shape of the NUCAPS profile was generally on par, missing the temperature inversion, not surprisingly. The SB LCL was very similar to the raob, but SBCAPE values were around 500 j/kg too high.

- Bucky

NUCAPS plan view shows warm mid levels

Near the time of the NUCAPS pass, warm mid level temps, above +10C bulged northward from Texas to the eastern two-thirds of OK according to regional RAP analysis.  Plotting of NUCAPS H7 temps revealed the warmest temperatures in the same area, though the warmest temps were a little cooler, 7-8C.  Temperatures were cooler to the east of the state and in the panhandles.

(NUCAPS H7 temps on 05/02)

-Forrest