Airmass Storms in FL

Focused on airmass thunderstorms this afternoon in Florida (Melbourne CWA) with the main threat being downburst winds. Took a quick glane at upper level water vapor imagery to analyze the synoptic environment. Noticed a shear axis between the drier air from the upper low moving south and the moist air moving west from Bermuda. Can also see some outflow from an airmass thunderstorm along the eastern coast of the CWA. The shear axis could help enhance lift over the next few hours (have noticed this feature over FFC quite often and it often enhances convective coverage.

Week 4 Day 3 Operations

Forecasters today will begin in the Sioux Falls, SD CWA monitoring an exiting MCS and looking for recovery for more strong afternoon convection. The other group will begin in the Melbourne, FL CWA monitoring sea breeze convection and GLM lightning trends for a while, with the possibility of moving later in the afternoon.

-Michael

Day 2 Wrap Up and Feedback

Forecasters wrapped up yesterday operating in the Flagstaff, AZ CWA monitoring monsoon convection throughout the area, and in the Green Bay, WI CWA monitoring a broken line of storms moving across the area. Feedback and comments on the various products are posted below.

ABI

Seeing the hail swath in the imagery was pretty cool

The clean IR and sandwich showing the cooling cloud tops in Arizona helped clue into the stronger storms

Looking at the differential motion in the three water vapor channels was nice for showing 3D structure

Simple water vapor RGB showed a shortwave trough stand out over Arizona that wasn’t apparent in the imagery itself.

The sandwich product has been useful

1 minute imagery over Arizona was very useful with the pulse convection giving a real-time trend of the cloud tops

Fire Temperature RGB caused fires to pop out pretty well, especially the large fire over California

Day Cloud Phase was useful for monitoring for cloud glaciation

CAPE wasn’t very useful due to underreporting

TPW continues to due very well with observed values

Cloud phase product was a little helpful for looking for ice clouds

ProbSevere

Worked pretty well in Arizona

Seemed more restrained than previous versions that maxed out probs earlier than this algorithm seems to

Like that it’s not as aggressive

Useful for SA with lots of storms

When the object size changed larger, the numbers would drop even though radar velocities and structure didn’t change

Doesn’t sample the racing gust fronts well at all since it tracks reflectivity

Adds value when examining storms

Love the readout and to see all of the information going into it

GLM

Want to be able to see the trends in a time series or something

Looked at groups for a little bit

Events and flashes seem to be what is used most often

The events seemed to give a bit of lead time on when ProbSevere started to increase

Had instances where GLM had a lot fewer flashes that like Earth Networks

NUCAPS

Experimental seems to be consistently better for looking at the boundary layer

Cap strength is something we a very interested in prior to convection which this type of sounding can be useful for

-Michael

Rain/hail swath in the wake of a high plains supercell

Cool loop of Split window difference with IR overlay of a supercell crossing southeast MT into northwest SD. In the wake of the supercell a dark swath is evident rainfall, and it looks like an even darker swath near the updraft may be associated with hail. A similar swath is evident with another cell moving into northwest NE.

-64BoggsLites

GRB Radar Velocity vs Prob Severe Object

One thing that was noted with the ProbSevere object...it was slow to keep up with the convective outflow as the line advancing across central WI accelerated.

-64BoggsLites

Another Prob Severe vs outflow example

In this example, a core of 55+ kt inbounds near 500 feet agl is approaching the GRB radar and moving out away from the probsevere object. Meanwhile, the object shows a decrease in wind potential to below 45%.

-64BoggsLites

Interpolated vs Non Interpolated GLM Events

From my use of both methodologies I think interpolated imagery tends to catch my eye better when zoomed out at the large scales. When zoomed in on individual storms the interpolated image did not make much of a difference in highlighting stronger storms.

JRM

On Wisconsin, on Wisconsin

We left OAX for the greener pastures of Green Bay. Convection was ongoing along a steep SW-NE thermal boundary at the surface. There was a strong surge of warm air in a tongue approaching GRB. Watched as velocities came up along a cell just west of GRB and issued a statement for strong winds.

Eight minutes later a second are of winds >30 kts appeared just south of the original cell, so a second statement was issued for this area.

At 2215Z the inbounds increased to 30-40 kts and the trend was increasing. Warnings were issued for second developing bow at 2221. I think this is a time when ProbSevere was misleading us, because ProbWind went down even as velocities were going up. I think this is because the size of the PHI object grew, so perhaps there was some averaging going on inside the shape. I issued warning due to low level velocity only.

At 2233, in an area with increasing lightning trends, MESH started increasing on the northern bookend. Issued SVR for 60 mph wind and 1" hail for area around Shawara co.

Six minutes later the storm really intensified. Still inside the warning box, the ProvHail increased to 95% and ProbWind increased to 94. MESH increased to 1.58", but left the warning as is in anticipation of melting.

Half an hour later, still satisfied wind threat (mainly) continues with the line behaving well and remaining inside SVR box.

Noted that velocities on the southern part of the line experienced a strong increase, in excess of 50 kts inbound in segment of the line heading toward Green Bay itself.

Warning expired, so I need to reissue for storm heading into the Green Bay metro. Hail threat very low, so increased wind threat to 70 mph due to velocities in excess of 60 kts as storm approached RDA.

-tvguy

GLM Lead Time vs ProbSevere

An increase in lightning within the interpolated 8km GLM group data was noted and preceded prob-severe's increase in probability for wind and hail by several minutes.

Looking at the gridded 9km data there was also an increase noted as well, although there remained some pixelation problems which could suggest there is no lightning in areas where it actually exists.

The radar loop below shows a 0.5 degree evolution of the convective line. During the time the increase in lightning was noted, a strong updraft developed with a suspended reflectivity core in excess of 65 dBz near 30 kft agl.

-64BoggsLites

Omaha has moved to Green Bay

The group of forecasters that started in Omaha's area have been moved to cover Green Bay, WI due to lack of storm initiation over the Omaha area.

-Michael