Author: Jim LaDue

Max Updraft preceding Max Reflecitity

Posted in Live Blogs on by Jim LaDue.

Late in the afternoon, as convection continued along the southern fringe of BTV’s county warning area, a storm cell began pulsing up and down.  This series of images shows how the max reflectivity on radar and the maximum updraft output from 3D-VAR began oscillating.  Maximum updraft strength from 3D-VAR would precede a peak in radar reflectivity by about 20 minutes.  We issued a warning for a southern BTV county, based on the Max Updraft data.  The storm produced 3/4 inch hail.

2205z.  Reflectivity is maximizing from a previous pulse, and current Max updraft values are less than 10 m/s.

2235z. Maximum Updraft values around 14 m/s. Max Reflectivity around 56 dbz.

2300z. Max Reflectivity back up to 60 dbz, while Max Updraft Strength continues around 18 m/s.

Dankers/Kearney

Update: 2012 May 16 22z

Posted in Live Blogs on by Jim LaDue.

Convection continues to be active in the Albany CWA keeping Brian and Julia active.  It appears that the moisture axis in the Hudson valley is contributing to storm intensification.  Things have quieted down substantially in Burlington’s CWA and no warnings have been issued by Todd and Stephen for over an hour.  They could move east to Gray Maine’s CWA, however there is no indication that storms will reintensify upon crossing CWA boundaries.  Or perhaps they could move to Taunton, MA’s CWA but storms are unlikely to reach there for another two hours.  Thus Stephen and Todd will continue their focus to looking at CI and Nearcast products on CONUS scale as they have done for the past hour.

Jim LaDue:  EWP week 2 coordinator

Tags: None

SVR for Burlington CWA

Posted in Live Blogs on by Jim LaDue.

We used MRMS data during storm interrogation and decided to warn for a storm over far northeast New York and far northwest Vermont.  As early as 1812z the MESH was indicating hail just over 1 inch while the height of the 50 dbz echo above -20c was over 5000 feet.  Warning decision was not made until after 1820z after looking at KCXX radar data.  1 inch hail reports were received from about that time.  Attached is a 4 panel showing the Max Expected Size of Hail (MESH), heights of 50 dbz echo above -20C, and reflectivities at the -10C and -20C levels.

Kearney/Dankers

Outlook: 2012 May 16

Posted in Outlooks on by Jim LaDue.

Yesterday’s outlook appears to be still on track.  One strong northern stream wave is approaching eastern NY and New England along with a significant cold front.  The front still has to interact with the axis of best moisture from the Hudson valley to the east and yet higher based convection is forming in the high terrain in northern PA to the Adirondacks.  Convection should consolidate once the front hits the moisture in 2-3 hours.  Deep layer shear is strong enough to generate supercells, however the majority of the convection may fall into small multicell forms, perhaps some bow echoes.  Low level lapse rates from the Hudson valley to the west are strong but midlevel lapse rates are somewhat marginal (6-7 c/km).  Thus I expect that large hail will be a threat though giant hail (>2.5″ diameter) prospects will be very small.  Tornadoes are unlikely given somewhat weak low-level shear (10kts).  Severe winds are much more likely as strong convective downdrafts are possible with the more intense storms.  We have both teams in the northeast; Todd and Stephen are localized to BTV while Brian and Julia are taking on ALY.  Convection has already initiated with the most coverage in BTV.

Meanwhile, steep, near saturated, low-level lapse rates have again initiated seabreeze convection along coastal NC.  New storms may form further southwest into coastal SC.  The Floriday play is somewhat muddied up by fairly dense high cloud cover.  However instability is quite sufficient for thunderstorms and the upper-level system is approaching from the west.

Jim LaDue: EWP week 2 coordinator

Tags: None

Daily summary – 2012 May 15

Posted in Daily Summaries on by Jim LaDue.

Today was one of those days where we ended in somewhat different locations than we intended.  Following the morning forecast, we had Stephen and Brian focus on Blacksburg, VA’s CWA while Todd and Julia took on Sterling, VA and the LMA site.  We were enthused about the possibility of severe multicells in both areas given the deep, rich moisture, decent CAPE and about 30 kts of deep layer shear.  However, the storms that formed remained weak with only a few lightning events per minute.  Apparently the weak lapse rates only become worse, likely because the area was on the subsident side of a weak wave lifting into New England.

After a couple hours of failed attempts at vigorous Deep, Moist Convection (DMC).  Brian and Stephen moved to the Davenport, IA CWA to sample DMC in a weak CAPE, steep lapse rate layer with 25 kt 3 km winds along a cold front.  Initiation was painfully slow as the environment was marginally conducive to DMC.  Yet by 6:30 pm storms intensified just enough to produce severe winds just south of Davenport.  3DVAR showed a good example of wind augmentation at 1 km around the south side of one small multicell just before the wind reports.  It also showed convergence from what appeared to be a gust front.  The base velocity 0.5 deg scan from KDVN showed the downburst in more detail.

Meanwhile we noticed that the Melbourne, FL area had a large pocket of strongly unstable, and unworked air surrounded by active outflow boundaries slowly converging on the CWA. Todd and Julia shifted to Melbourne and set up for a better than expected event.  They issued a severe thunderstorm warning for rapid development just northwest of Melbourne.  The LMA showed rapid increases in lightning rates up to 20 fl/min I believe.  Meanwhile 3dVAR showed some rotation around 5 km MSL.  The CI product from UW highlighted some of the initial phases of that thunderstorm.  Later on, one of the storms near Titusville began to rotate.    Soon KMLB base velocity showed a strong azimuthal shear and a tornado warning was issued.  3dVAR had a gap between two domains that prevented early detection until the 3dVAR northern domain was shifted south.  The 3dVAR will need to be redone for a later case review.  Meanwhile the UW CTC product didn’t flag the storm as it developed.

The IA case is a great example of a weak CAPE, marginally convective event with severe winds.  The MLB case is a good severe GOES-R mini scenario for AWOC.

Jim LaDue:  EWP week 2 coordinator

Tags: None

EWP STATUS FOR 16 MAY 2012: 12-8pm SHIFT

Posted in Operations Status Message on by Jim LaDue.

EWP STATUS FOR 16 MAY 2012:  12-8pm SHIFT

Based on the available 15 UTC SREF guidance, the east coast again appears to be the best potential for deep, moist convection (DMC).

We have three potential plays of concern.  The first area may be New England as the northern stream system affecting IA to WI today moves to the east and begins to impinge on better moisture along the eastern Seaboard.  With increasing midlevel winds, the deep layer shear will increase enough for a supercell threat as long as the instability is not prematurely extinguished.  The second area will be further south along the coastal regions of the Carolinas.  Similar to the past few days, substantial moisture and marginal midlevel flow from the stalled trough may produce enough shear for organized small multicells.  Boundary interactions will provide for an interesting session for anticipating severe DMC.  The third area will be in FL again as the southern TX upper-tropospheric wave moves eastward.  Mid- and upper-level flow will also be marginal to perhaps sufficient for supercells, especially in regions where low-level backed sea breeze flow augments deep layer shear.

All of these potential targets will likely initiate DMC early enough to warrant a 12 – 8 pm shift.

Jim LaDue, EWP2012 Week #2 Weekly Coordinator

Tags: None

20120515 – 2125z update 1st warning of the week

Posted in Live Blogs on by Jim LaDue.

The first warning of the week was issued by the MLB team for a storm just northwest of MLB.  The MRMS and 3dVAR shows some indication of rotation with that storm between 3 and 6 km.

Updraft helicity and merged azimuthal shear layers and units are different.  How does one compare between the two?

Jim LaDue: EWP week 2 coordinator

Update: 2012 May 15 1954z

Posted in Live Blogs on by Jim LaDue.

The western target is now growing enough cumulus to have one of the teams move west.  Brian and Stephen will be localizing to Davenport, IA CWA to take the best advantage of evaluating CI along the cold front.  CAPE is weak but lapse rates are high.

Tags: None

RNK 19:15UTC

Posted in Live Blogs on by Jim LaDue.

Although this was outside of our CWA, the CI product did a nice job of detecting a developing storm along the sea breeze front on the Carolina coast.  At 18:15UTC, CI indicated a 90% (red) area.

45 minutes later, at 19:00, the visible image showed a full-blown storm with a wide anvil.