Notable Parallax Errors on GLM

There were notable parallax errors noted on the supercells moving east across the southern portion of the ALY forecast area.

1919Z GLM Flash Density/1920Z ENTLN Plot showing parallax errors

Alex Brown

ProbWind Model

The ProbWind model has done a good job handling the wind potential along the QLCS moving across NY/PA into northern NJ. Of course, this is a relatively simple example, but the base velocity from KDIX (Fig 1) is indicating wind speeds in excess of 70 kts (at a beam height of 8 kft). Meanwhile the ProbWind model (Fig 2) is indicating the probability of severe wind at 85%. This is much higher than the wind numbers I have observed from other storms.

Fig 1. KDIX Base Velocity at 1940 UTC observing wind gusts at or slightly above 70 kts.

Fig 2. ProbWind at 1936 UTC indicating 85% probability of severe wind.

Afternoon Forecast Trends

Working ALY desk today. A frontal boundary is slipping south and east across the southern portion of the forecast area. Significant convection is already occurring along the boundary including a few large hail producing supercells. Moderately unstable airmass is shown over the region south of the boundary, with CAPE values on the order of 1500-2000 J/kg. Strong bulk shear around 60kts is more than sufficient to produce the rotating storms that are evident.

Alex Brown

19Z surface plot 1926Z visible satellite clearly show boundary & intense convection

18Z AllSkyLAP CAPE showing moderate instability over far southern forecast area

18Z NUCAPS sounding over far southern forecast area

Very High ProbTor Value

In the image below, note the high ProbTor (85 percent by sampling) at 1850z over southern Columbia County in the ALY CWA (lower right panel). This  was a rapid increase from 27 percent 10 minutes prior. I believe the ALY office had already issued a TOR warning on this cell, but the ProbTor product should increase confidence.

A.Cope

Convective Initiation

Working the ALY forecast area today. Strong/severe convection developed rapidly around 18z ahead of the main line over PA. Loop below shows
probability of severe storms, overlaid on VIS imagery.  Strongest storms  developed along Ulster, Greene and Columbia counties, but not too well anticipated by the CI products which were highlighting the cu field farther SW.
A.Cope

ProbTor "cell" size

The inclusion of the MRMS data into the ProbTor product has really turned it into a good situational awareness tool when triaging storms on the wide view of the radar.

Fig 1. ProbTor product at 1914 UTC.

However, linear storms can lead to an undesired result when it comes to the identification of storm cells. This is generally OK in a severe wind threat, but the tornadic potential is usually quite limited. In the example above, the identified cell is 56 miles long. That doesn't provide a lot of value other than to draw ones eyes to that general area. Having a way to reduce the size of detected cells, especially in QLCS events would be a great improvement.

wall_cloud

NUCAPS data planes

I have found the NUCAPS soundings to be quite beneficial, especially in areas where radiosonde data is sparse. This will be quite useful in my CWA (MEG) where the nearest sounding is roughly 150 miles away. Having the METOP A/B data at the WFO level would help offset the temporal issues.

I think the gridded NUCAPS will be useful as well, especially on when viewing on a plane like we do many other fields. However, I have found the data planes in the volume browser to be quite cumbersome and not exactly intuitive. I think that using more standard levels like most models/observations would be beneficial to the user and would ensure more use in the field.

wall_cloud

Forecast 5/15/18

Moderate instability exists today across northern PA, southern NY, even extending east into portions of MA/CT/NJ. AllSkyLAP CAPE values are generally in the 1500-2500 J/kg across the Mount Holly CWA with surface temperatures already in the mid 80s to near 90 degrees. Strong unidirectional flow aloft is observed across the region with slightly backed low-level winds in the warm sector. The resultant deep layer vertical shear of 35-40 kts (0-6km BWD) will help maintain the QLCS moving east at this time. Strong, organized bowing segments are likely within the QLCS which may result in widespread damaging wind across the CWA. Large hail cannot be ruled out, but this is certainly not the primary concern today. In addition, a few tornadoes will be possible should winds remain backed ahead of the main line. This system will propagate eastward across the CWA very quickly this afternoon.

wall_cloud

GLM Parallax

The image below compares cloud lightning flashes from Earth networks with GLM total energy. The GLM image gives a much more complete picture of the extent of lightning, however there is a noticeable north/south discrepancy between the two. The GLM max just southeast of the main line is shifted northward by about 10 miles relative to the ENI lightning cluster.

A. Cope

Week 3 Day 2 Operations

The forecasters will be operating today in the Northeast starting out in the Albany, NY and Mount Holly, NJ CWAs. We will be monitoring a fast moving convective line across Pennsylvania and New York and later moving into the Boston area with the potential for damaging winds and a few tornadoes.

-Michael