- Outbreak of Severe Storms Including Tornadoes – Thursday Afternoon Into Friday Morning.
- Damaging Ice Storm Likely Across Georgia, South Carolina
- Major Winter Storm To Impact Southeast Then East Coast.
- New SREF Accumulated Winter Precipitation Products
- Significant amounts of freezing rain likely across the New York City area tonight and early Wednesday
- Chris on Major Winter Storm To Impact Southeast Then East Coast.
- chris on Major Winter Storm To Impact Southeast Then East Coast.
- Mike Dross on Updated: Ice Storm Increasingly Possible for Western/Central NC/VA Friday/Saturday
- Michael mefford on Updated: Ice Storm Increasingly Possible for Western/Central NC/VA Friday/Saturday
- Mike Dross on Remarkable radar data from the El Reno EF5 Tornado.
A zone of of prolonged freezing rain will extended the I-20 corridor from Atlanta to Augusta to Columbia, SC. Model freezing rain liquid equivalent totals in this area exceed 2 inches. While drip loss will be relatively high with accretion efficiencies likely only being in the 30-40% range due to the high precipitation rates and the temperatures likely remaining close to the freezing point, this still yields radial ice accretion amounts of .50-75″ which would cause widespread electrical distribution disruptions and tree damage.
Here are the latest Freezing Rain Graphics.
A strong winter storm will bring a variety of winter weather to the Southeastern U.S. as an upper level low develops across the mid-south, in combination with a cold air damming event. A strong coastal low will strengthen and move up along and just off the Eastern seaboard and bring heavy precipitation to the Mid-Atlantic and into the Northeast
New Short Range Ensemble Forecast (SREF) Mean Accumulated Winter Precipitation have been added. They are:
Snow change from previous run (dProg/dt)
Ice Pellets (Sleet)
They can be found in the drop down menu on the SREF model page under “Forecast Parameter (Mean)”
2/5/14 1:45 Z
Freezing rain will moving into the populated region of New Jersey and New York City around midnight (2/5/14) and will persist until around noon Wednesday. Temperatures in the New York city metro area are expected to remain near or slightly below freezing the duration of the event. Just northwest and west of the downtown area, slightly colder surface temperatures are likely.
Total precipitation amounts of 1.00-1.25″ is expected. A significant amount of drip loss will occur due to the heavy precipitation rate and the small air temperature delta to freezing point. Where temperatures are likely closer to 29 or 30 degrees just west and northwest of the city, ice accretion amounts of 1/4″ to as much as 1/2″ are possible and could lead to a significant amount of power outages, if ice accretion amounts surpass 1/3″.
The GFS Model will be upgraded from ~27KM to ~13KM this summer. The High Resolution Rapid Refresh Model (HRRR) will become operational later this year. Power Point Link (NCEP)
In preparation for these and other expected increases in weather processing volume, we have been adding additional computing hardware to handle this data increase. Using redundant Enterprise HP Proliant hardware in a 24/7 staffed SAS-70 Tier 1 Data Center, ensures we will be ready to handle the next generation of weather data. Below is an image of a few of the servers & equipment that deliver Wright-Weather.com products to you.
Quite a bit of uncertainty, but the latest data suggest the potential for severe thunderstorms and possible tornadoes across Eastern Texas and the Deep South Saturday as a strong, negatively tilted, shortwave ejects across Texas. Stay tuned over the next couple of days if you live in this area.
Update: 12/20/13 12:40AM EST
After reviewing the 00Z model guidance, it appears that the instability will be somewhat limited on Saturday, due to clouds and marginal lapse rates. Severe thunderstorms with damaging winds are likely to develop across East Texas during the morning and spread quickly eastward during the day. 0-6Km shear vectors are large and 0-1km helicity values will be locally high, so some low-top supercells are likely, including the risk of a few tornadoes. But given the expected limited instability, SFC CAPE <1000, a widespread outbreak of tornadic supercells seems unlikely. The threat of damaging winds is high however, as the low level jet increase to over 70kts during morning and early afternoon.
850 Wind Late Saturday morning near 80 Knots
The numerical models historically have had a very difficult time trying to predict cut-off lows across the Southwestern U.S. that eject and try to phase with northern stream energy.
This is the case now, in regards to next weeks, all important holiday week forecast. The GFS Operational has consistently forecast a strong Nor-Easter with inland snow and a mixture/rain near the coastal areas & major metros in the Northeast.
The GFS Ensembles have trended in favor of the GFS operational, recently. The ECMWF operational is moving a much weaker system more off-shore with less of an impact. The differences between the two can be seen by examining the upper air charts (500mb) and see how the models handle the northern and southern streams (height/vorticity).
The ensembles will be the most useful guidance over the next day or so as we try to get a handle on the likelihood that the streams will phase and to what extent. Until then, I would be very leery of anyone telling you they know which solution is correct or what exactly is going to happen. These patterns are very complex and historically very challenging for the models to accurately simulate at these time ranges (4-5 days out).
GFS Ensemble 500mb Height & Vorticity 12z Wed
GFS Ensemble SFC Pressure & Precip 00Z Thu.
ECMWF 850 00Z THU GFS 850 00Z THU
Notice the large differences. The GFS develops a huge cyclone over the Northeast while the ECMWF does not, because the ECMWF does not completely phase the two streams.
Severe Weather Outbreak Likely Friday Afternoon/Night Midwest – Southern Plains
As an upper level low begins to move eastward, the strong core of the mid and upper level winds will rotate around the upper low. An increasingly favorable kinematic environment for supercells and potentially strong tornadoes will develop from Central Illinois/Central Indiana through Southern Missouri into Eastern/Central Oklahoma and Northern/Western Arkansas.
The area at greatest risk for strong tornadoes is from Central/Eastern Oklahoma through Southern Missouri into Central Illinois. Although there will likely be AM storms, some severe, the storms that will develop Friday afternoon and move into Ohio-Valley during the overnight hours are the ones that pose the greatest risk for that area. Boundaries from earlier convection in the day will likely focus localized helicities values over 400 m^2^s which will enhance the tornado potential with storms that develop in non-linear modes. Bulk Richardson Shear values favor supercell storm modes across these areas, at least initially.
Other storms will likely form further south across Oklahoma where the instability will become extreme with surface capes over 5000 and shear values in excess of 40kts. CIN will drop below 25 j/kg by afternoon and supercells should form with the aid of an approaching shortwave. With LCL’s AOB 1000 meters, tornadoes are quite likely, especially across Northeastern OK.
The Maximum Updraft Helicity product from the 4km WRF/ARW has been consistently generating strong supercells across OK, MO, IL Friday Afternoon & Evening.
1 Hour Max Updraft Helicity. Indicate Rotating storms develop late.
Max 1 Hour Updraft Helicity from WRF-ARW
WRF-4KM Simulated Radar 23Z Friday
High Surface Dewpoints work northward into IL/IN feeding storms.
Surface CAPE is quite high.
Surface Low over MN and Secondary Low over SW OK will help back Low Level Winds.
Supercell Composite Parameter indicates likelihood of rotating storms from OK northeastward into IL.
Significant Tornado Parameter indicates risk of strong tornadoes.
0-1km Helicity 03Z
250mb RRQ of Jet will enhance Vertical Motion
Upper Level Low will move Eastward with cold pool and wind max
St. Louis, MO Forecast Sounding for Friday Evening. Small Cap, but supportive of Supercells and possible tornadoes
GFS Forecast Sounding for Springfield, IL for 00Z. Again kinematics and thermodynamics supportive of supercells and tornadoes.
Extreme Instability at Oklahoma City per the GFS Forecast Sounding
The May 31st EF5 El Reno Tornado that killed several storm researchers was sampled by ground based mobile X-band doppler radar (RaxPol) with very high resolution and found extreme wind speeds of almost 300 mph and rare satellite tornadoes. Other conventional fixed based NWS and FAA radars also captured remarkably high velocities and signatures.
Below is the Terminal Doppler Weather Radar from Oklahoma City (TDWR). A C-Band Radar with a high resolution receiver (250 meter resolution data displayed) and it appears to capture an apparent reflectivity minimum in the center of the tornado at the *exact* same time that the RaxPol indicated the same feature in the tornado. This is quite remarkable considering the distance from the radar is 26 miles. This reflectivity minimum is likely caused by descending air within the tornado and centrifuging of debris and precipitation in this case.
The National Weather Service WSR-88D in Norman, OK recorded some of the fastest winds I am ever aware of. I am quite sure these winds are legitimate. Below is a screen shot of the tornado at 23:24Z
El Reno Tornado before it became extremely large and wrapped totally in rain. Courtesy of Justin Drake @JustonStrmRider
With mobile Doppler radar units that have become available in the past 20 years that have extremely high resolution, we have been able to discover tornadic wind speeds in a few of the sampled tornadoes that have approached or in one case exceeded 300 mph. The recent El Reno tornado on May 31st, 2013 was another example of one of these.
Since the force of the wind does not grow linearly, rather it is squared (wind speed^2), these extreme wind speeds over 200 mph can cause unbelievable destruction. Since the kinetic energy is in the same arena as a small nuclear bomb, should one of these ”Super Twisters” hit a densely populated urban environment the destruction would be exponential compared to a lower category tornado. I created a graph to try to visually demonstrate the energy release or damage potential of the 2013 El Reno tornado as compared to just a few other recent tornadoes that have had good NWS storm surveys and tornadoes that had mobile Doppler radar measurements. There is a cluster of Super Tornadoes in the upper right hand portion of the graph that illustrates how much more destruction they can create than an EF3 or EF4 tornado if they encounter buildings, cars or people.
I think it also illustrates that there is a huge range in the EF5 scale. Maybe now that we have entered the era of reliable remote sensing and we know there are tornadoes with wind speeds near or even above 300mph and the energy release is so much greater than a 201 mph EF5 tornado, the idea should be at least entertained about adding an additional(s) EF categorie(s) to account for these rare, but extremely violent tornadoes given the their potential destruction and design limits required to survive them.
Click graph for larger image
An anomalously strong late spring upper level trough will develop along the Eastern U.S. Coast by Friday. Two shortwaves, one ejecting out of the southern stream over California, will at least partially phase with a second shortwave that drops southward into the Great Lakes on Thursday. These will combine to strengthen a surface low that will traverse from Iowa eastward to the New Jersey Coast.
A two-day event is expected as severe convection will likely generate near the surface low Wednesday afternoon across Illinois and Indiana where the best forcing will exist, however further east across Ohio and West Virginia additional severe storms may develop with the aid of warm air advection and a mid level wind max in the northwest flow, during the afternoon. If discrete convection develops across Ohio/Western West Virginia on Wednesday afternoon there could be supercells and possibly strong tornadoes, given the favorable shear and other parameters. This is well ahead of the main forcing of the the surface low back to the west.
Intense convection is expected to develop across Illinois and Indiana and track eastward during the overnight hours. As the surface low deepens, warm air advection will continue to help destabilize the atmosphere near the warm front which is likely to be near Northern Ohio into Western Pennsylvania . A greater risk of significant tornadoes exist along this boundary. Just north of the warm front elevated convection may produce large hail and damaging winds.
Additional storms may develop further southward into Southern Missouri, Kentucky and Tennessee.
As the upper level shortwaves begin to phase, per the NAM. The surface low is expected to slow somewhat and should allow for some destabilzation across the eastern portion of Virginia, Maryland, Pennsylvania, New Jersey during the afternoon.
Wind fields will support supercells and possible tornadoes from Central Pennsylvania to New Jersey southward into the Carolinas . The best parameters for significant tornadoes on Thursday will exist near the warm front across Pennsylvania, Maryland, Delaware & into New Jersey.
*All of this is highly dependent on surface heating and interaction with prior convective outflow boundaries, none of which the models can properly resolve at this time range.
Below are some of the products used to create the outlook.
NAM Forecast Sounding for Columbus, OH Wednseday Evening.
Forecast Sounding for Baltimore, MD for Thursday Afternoon at 2PM EDT
NAM Sounding would support severe storms and possible tornadoes.
Complicated forecast for the Ohio-Valley into West Virginia and Western Pennsylvania, Wednesday into Thursday Morning. As indicated in last nights discussion, synoptic forcing is very strong and will create favorable conditions for a large area of severe weather as an intense low pressure for this time of year, moves across the Ohio Valley. The primary forecast problems are the convective mode that the storms take once they develop and whether the downstream ambient environment is contaminated by earlier convection that will disrupt the inflow and stabilize the boundary layer. This is exactly what happens with the WRF-NMM and WRF-ARW 4KM models, each a little bit differently. The WRF-4KM NAM CONUS Nest does not, and creates very little convective contamination prior to the main system arriving and develops a very dangerous environment across IL/IN/OH/ Western PA that would support a widespread severe weather event with supercells. While not explicitly, it would likely yield some tornadoes given the intense parameters it is generating.
Below are some animated GIF’s from the WRF-NMM to illustrate the forecast issue of convective contamination of the environment prior to the main forcing/convection related to the surface low. If this AM convection does not develop across WV/VA as indicated, the stable outflow may not be near as strong and may not provide the cool theta-e values and therefore not weaken the main convective system as much or at all when it arrives late Wednesday night.
WRF-NMM Radar Simulation. Note Convection that develops across WV/VA AM Hours Wed Morning.
WRF-NMM Note the Theta-e minimum associated with the AM convection across WV/VA mountains that works westward and helps weakens the approaching convective system late Wednesday night as it arrives in OH.
Even as it is, with some possible convective contamination. The mesocale models are generating some strong indications of a wide spread severe weather event.
Across the Ohio-Valley Wednesday into Wednesday night, the 0-1km helicity and the 0-6km shear will increase as the surface low deepens and the upper level shortwave approaches. Kinematic forcing will favor the formation of supercells and possibly tornadoes over a fairly large area, but the most favorable location will be just south of the stationary front/warm front which will maximize the 0-1km helicity.
Here is just one of the Updraft Helicity products from the various mesoscale models. This is from the WRF-NMM. It’s developing a long lived Supercell from just west of Chicago and tracking it southeastward. Other supercells develop across Indiana and Ohio. This is one of the longest and most intense updraft helicity values I have seen since observing these parameters.
Forecast Sounding 40 Miles South of Chicago, IL 01Z Wednesday Evening. WRF-4KM NAM Nest
Forecast Sounding near Wooster, OH this evening at 00Z. Very Unstable atmosphere in place ahead of main forcing. Supercells and tornadoes are possible if convection can develop ahead of main convective system.
While the threat from widespread damaging wind is certainly high and linear mode convection may very well be the primary mode of convection for the duration of this event. I feel that there very well may be a period of time where there are either discrete supercells or embedded supercells with in a line. Given all the parameters, I believe the tornado risk is quite high along and just south of the stationary front from Central IL through IN into OH. This is a highly conditional forecast, since convective contamination from earlier storms may affect the environment or if the system becomes a large bow-echo or derecho very early in the evolution, then the tornado risk is greatly reduced.
Here is a map outlining the risk area of tornadoes based on all the available guidance through 05Z.
Did the 88D at FFC capture a Tornado ? Dual Pole data may have picked up some debris. Survey may tell later today. Here is a screen shot I took last night while the event was unfolding. The velocity data was not very compelling, but in the previous 3 volume scans there were much better indications of a circulation.
Click images for much larger view
Update: I pulled the archive data from last night. Here are previous volume scans. You can see the progression of the development of the CC min & other radar data.
An apparent brief touch down of a tornado in Central North Carolina yesterday evening was detected by the Raleigh, NC WSR-88D Radar. The RDA was fairly close to the storm with the 0.5 degree beam altitude only around 1390 feet.
While the NWS survey has not yet been completed, it appears this will very likely be an EF0 or EF1 tornado, based on the damage reported, photos and radar data.
Update 2:10 PM EDT: NWS just confirmed EF0 with 85mph winds. Path length 1.25 miles / 150 yards wide
The 22:31:59Z volume scan had a small, but defined TVS with gate to gate shear of ~81kts (+57/-24) and a well defined hook echo. It also developed a significant correlation coefficient minimum which was co-located with a reflectivity maximum in the hook where the TVS was also centered.
All of this convinced me, that there was indeed a tornado on the ground and in progress. I quickly put together a “tweet” and sent it out at 22:36Z indicating that we now had a tornado on the ground.
I also submitted something to the effect, on RAH NWSChat, about a possible debris ball developing on radar.
Shortly there after we started receiving verification of damage and sightings of the tornado.
This is another example of how useful the Dual Polarization data can be when looking for Tornado Debris Signatures. Even for locating relatively “weak” tornadoes. Looking at the dual polarization data, it appears the “debris” was lofted to an altitude of around 2600 feet. My thinking is that much of this “debris” is likely tree leaves & foliage from the wooded areas where the tornado crossed, as well as, some other materials.
Click images to enlarge
Photos of the wall cloud ( Credit: WRAL)
Damage to a home in Youngsville, NC
Update: 2/4/2014 03:00Z
Models have trended originally from a Miller B system to a strong Miller A system yesterday that brought heavy winter precipitation up the east coast from NC to Maine.
Today the models have largely backed away from any inland development and any phasing would take place off-shore and on Sunday. The pattern I outlined below, I wrote about 3 days ago, is not expected to materialize as the models had alluded it might. The confluence area across the Eastern North America does not look like it will be very strong and the short wave coming into the U.S. is likely to be somewhat weaker than earlier projected and will not dig into the Southwestern U.S.
The end result is a much different scenario, with little or no cold air damming and possibly no precipitation.
The ECMWF and GFS deterministic & ensembles have been supportive of the synoptic setup that is favorable for a wintery, cold air damming event across NC/VA the end of next week with a mixture of precipitation, though predominantly freezing rain or sleet.
Having forecasted these types of events for many years as an operational meteorologist for Duke Energy, I had to often look for synoptic clues many days out rather than relying on explicit model output of things like 2 meter temperatures or precipitation type values that would indicate a significant icing event.
Models generally do not handle very cold air at low levels, particularly well. Especially the global models as they have a smaller number of vertical levels near the boundary layer where a lot of the shallow very cold air exist with arctic air masses. The global ensemble models have even less vertical levels than the deterministic models making them often poorer choices for depicting things such as cold air damming events.
So while we are some 6-7 days from this potential event, there has been a consistent theme among the global models that makes me believe that a growing risk exist of winter weather and potentially a significant amount of freezing rain Friday into Saturday.
Historically, one of the primary mechanisms we have observed in NC that accompany significant icing events, is an upper level confluent flow across the Northeast or Eastern Canada that is maintained though much of an event. This causes surfaces pressures to remain high and re-enforces cold air at low-levels down the Piedmont of Virginia & North Carolina. Future model runs will need to be monitored to see if this trend is maintained.