EWP Blog – Page 288 – Spring Experiments & Beyond

3DVAR shows storm characteristics increasing ahead of storm splitting and deviant motion

Posted in Live Blogs on May 24, 2012 by Greg Stumpf.

The 3DVAR output showed strong increases in storm top divergence, updraft helicity, and maximum updraft speed in the 2245z image associated with a thunderstorm in Buchanan County in northwest Missouri. Subsequent to these increases the thunderstorm updraft split (left mover died quickly) and the storm turned to the right over the next several images, as shown in this image of the maximum updraft composite. The brightest image represents the current image while a history of previous images is shown in subdued colors.

3DVAR used over NW Missouri

Posted in Live Blogs on May 24, 2012 by Greg Stumpf.

A line with strong to severe storms continues to push rapidly to the east. The environment is favorable for rapid storm organization, given 60 kt deep layer shear and tongue of 2000 plus J/kg SBCAPE sneaking in from the SW.

2405_3DVAR2230Z — 2230Z: Max divergence (upper left), composite updraft max (upper right), updraft helicity (lower left) and max vorticity composite (lower right)

2405_3DVAR2237Z — 2237Z: Max divergence (upper left), composite updraft max (upper right), updraft helicity (lower left) and max vorticity composite (lower right)

At 2237Z, the composite reflectivity image was added (upper right) with core refl. aoa 70 dBz just where 3DVAR indeed had the most severe cell development along that line over NW Missouri.

Helge

Harrison County MO CTC Lead Time

Posted in Live Blogs on May 24, 2012 by Kristin Calhoun.

The following CTC image led to the issuance of a warning at 2028Z. Severe hail signatures were noted with storm at 2112Z and severe hail was reported at 2130Z.

Quarter-sized hail reported in Decatur County, IA

Posted in Live Blogs on May 24, 2012 by Kristin Calhoun.

MESH appears to have given us as much as 20 minute lead time before the 1.00 in. hail report. Decatur County is along the northern swath of hail.

HIRSCH

OUN WRF on time with initiation over NE Kansas

Posted in Live Blogs on May 24, 2012 by Greg Stumpf.

Thunderstorms continue to build rapidly to the SW along the cold front with initiation underway around 2145 Z over NE Kansas. It is amazing how well the OUN WRF captured the initiation:

2405_2130Z_OUN WRF — 2130Z OUNWRF precipitation and updraft helicity (upper left)

2405_2145Z_OUN WRF — 2145Z OUNWRF precipitation and updraft helicity (upper left)

2405_radar_topeka — Radar Topeka at 2142Z @College of DuPage

Timing was excellent with placement just slightly off to the south. This model forecast would have helped forecasters a lot to pinpoint area of initiation well ahead.

Helge

3DVAR indicates thunderstorm strengthening

Posted in Live Blogs on May 24, 2012 by Greg Stumpf.

The 3DVAR products indicated strengthening of this thunderstorm with both the updraft helicity and maximum updraft values spiking on the 2140z image. This thunderstorm had previously caused wind damage (downed power poles) across southern FIllmore county. The values at 2140z were higher than those previously (as shown by underlaid history tracks) so a severe thunderstorm warning was issued for the potential for strong damaging winds.

UPDATE: Emergency managers reported widespread tree damage within the community of Winona, in the northern portion of the warned area, a lead time of 17 minutes. Dime sized hail was also reported within the warned area in southeastern Winona County.

Impressive Cld top cooling rate, Iowa

Posted in Live Blogs on May 24, 2012 by Greg Stumpf.

Severe convection currently evolves along the cold front over C Iowa with Cld top cooling product showing impressive cooling rates below -65 K/15 min e.g. over Warren and Polk counties.

2405_CIowa — Cld top cooling rate (upper right) at 2032 Z

Helge

Domain Update

Posted in Live Blogs on May 24, 2012 by Kristin Calhoun.

About 2100 UTC we gave up on lightning in the east coast domains (saw a max of 2 flashes / min during our time there) and re-localized to Des Moines, IA (McKinney & Kleinsasser) & La Crosse, WI (Strassberg & Hirsch) with our observers working Pleasant Hill, MO.

Storms are already ongoing with CTC rates as low as -50 C for multiple storms and we expect some SVR warnings shortly.

-K. Calhoun, Week 3 Coordinator

IA_ctc_2040utc — Cloud-top-cooling in s-central Iowa at 2040 UTC

SimSat has problems with tropical low

Posted in Live Blogs on May 24, 2012 by Greg Stumpf.

A weak tropical low moved from Cuba to the NE during the daytime hours and was forecast to affect far SE Florida. Comparing SimSat and real IR/WV data, significant differences can be seen especially regarding the cirrus canopy. The main reason for the differences may be the much stronger development of this depression than expected 21 h ago. NHC also increased probs to 40 %, indicating a consolidating system. This evolution may have resulted in a better defined depression’s center with stronger convective development. Therefore those products may have to be used carefully for tropical lows, which reveal stronger intensification rates compared to what models forecast.

2405_tropical moisture — SimSat vs real IR/WV data

Helge

Iowa CTC Lead Time

Posted in Live Blogs on May 24, 2012 by Kristin Calhoun.

The cloud top cooling product in central Iowa indicated nearly 40 C/15 km of cloud top cooling for a storm in Boone and Story counties. This product preceded intense radar reflectivity in the area by nearly an hour.