Archive for April, 2012

Tornado outbreak across central Plains verified!

As mostly expected, a tornado outbreak clearly verified over the HIGH risk area yesterday/last night, though less activity over northern parts due to extensive MCS on going from earlier activity. The main robust long-track supercells with violent tornadoes occured across parts of S KS into NNW OK. Below are several videos found on youtube from many fellow chasers…

http://www.youtube.com/watch?v=YiLL2XujUiU
Video © Davis Reimer, Jenny Brown

http://www.youtube.com/watch?v=S_QRG-TsfBc
Video © TWISTEX

http://www.youtube.com/watch?v=bYT1DZ7udkg
Video © Heidi Farrar, Dave Demko

http://www.youtube.com/watch?v=d-SlhQve1pk
Video © unknown author

http://www.youtube.com/watch?v=IcLmeD_NLdA
Video © Jeromy Carter

http://www.youtube.com/watch?v=bz0QisLgSnQ
Video © University Kansas

http://www.youtube.com/watch?v=e0RMXC80EcA
Video © Brandon Ivey

http://www.youtube.com/watch?v=JAUX-zin06g
Video © Dan Robinson

http://www.youtube.com/watch?v=T5X_nphzSjQ
Video © Chris Sanner

http://www.youtube.com/watch?v=C55L-q5JbVM
Video © Justin Teague

http://www.youtube.com/watch?v=HD-4GIEDfbg/a>
Video © Tony Laubach

http://www.youtube.com/watch?v=USCZsUEAHTg
Video © BNVN

http://www.youtube.com/watch?v=-IUTAwpV3N8
Video © BNVN

http://www.youtube.com/watch?v=gKzxhIFR37E
Video © BNVN

http://www.youtube.com/watch?v=RTb6A3XKCdM
Video © unknown author

http://www.youtube.com/watch?v=5TsbCSErWpw
Video © BNVN

http://www.youtube.com/watch?v=OIeweEDsrRQ
Video © Unknown author

http://www.youtube.com/watch?v=7a_QpIzyUN4
Video © BNVN

http://www.youtube.com/watch?v=BI8CGzXgBvY
Video © Mike Wilhelm

http://www.youtube.com/watch?v=gCAACPIeUhU
Video © WX5PJB

http://www.youtube.com/watch?v=bquzRTyOxuk
Video © Stevin Bessette

http://www.youtube.com/watch?v=o1X7DyA-t6c
Video © WX5PJB

http://www.youtube.com/watch?v=IiQBQxcUGNE
Video © TVNweather

http://www.youtube.com/watch?v=30LqxVzpEow
Video © unknown author

http://www.youtube.com/watch?v=SaWaNftg3UQ
Video © Dustin Wilcox

http://www.youtube.com/watch?v=3UGonOVyOMU
Video © unknown author

Unfortunatelly there were also several deaths, 5 people killed so far in tornado that hit Woodward, OK at early night!

Stay tuned!


Global patterns and an outlook for month of April!

**NOTE: This post has been made on the very last days of March, so keep in mind some maps are not refreshed to the last data, but overall outlook remains the same**

ENSO is now well neutral. It will stay like this for a while, most likely with a slow upward trend to en El Nino. But as this is April outlook, we will will be looking only at April values of ENSO.

Current state:

The CFS version 2 forecast, keeps it neutral somewhere until June.

SOI is also an important feature here. It is also in neutral values at the moment, with a downward trend expected. At least through April/May, it should stay neutral, with a faster drop probably in May, preceding an El Nino development, as suggested by CFS and ECMWF ENSO Anomaly forecasts.

When both of these global features are normal, the Madden-Julian oscillation has the strongest impact on the pattern. Strong MJO activity is often observed around 6-12 months prior to an El Nino cycle. Besides the neutral ENSO, this helps to explain an obvious pattern teleconnection in north hemisphere, when comparing MJO phase composites with the actual patterns in March. Detailed March pattern analysis will be added as soon as reanalysis maps become available.

MJO Forecasts take it into phases 7,8 and 1.

The phase 7 will soon end, so since phases 8 and 1 seem to be a bit longer lasting, we will focus more on that.

This is phase 8 composite. The main features here are ridging over USA, with blocking over Greenland into Canada, ridging extending into Alaska, troughs over East coast, quite deep lowering over northern part of Europe, with ridging further south. Also keep an eye on the Asian features.

This is CFSv2 500hpa anomaly, weekly forecasts. Phase 8 should be quite strong and lasting somewhat like the first week in the forecast. To be honest, looks like a good match, with some differences over USA West coast and Asia, due to the forecast starting at April 1st and phase 8 starting around April 3rd.

Phase 1 will probably be quite fast and weaker, so not much similarities expected, except for Pacific.

Composite for the phase 1.

The forecast (please refer to the CFS weekly forecast above) is still somewhat reflecting the strong phase 8, with Pacific in a Phase 1 state, since it is the closest to MJO.

It is still a slight mystery where MJO will turn after phase 1, but monthly forecasts are suggesting its absence around middle to late April, with a possible return into phases 4-5 in May. But thats whole month in advance and trends will be monitored prior to the next outlook.

With ENSO in neutral, SOI in neutral, and MJO absent, it is seemingly possible that the trend of the first half of the month will continue.

Lets look at a few CFS forecasts.

This is global 700mb anomaly. Europe lower heights, Greenland and Alaska and W CONUS blocking, and USA East coast troughing, have MJO phase 8 written all over it…

Looking at week 3 and 4 CFS forecast, is not really reasonable, since it is very unreliable, but we will look for the main features just to see what it is suggesting, compared to what is expected of MJO. Both weeks are quite interesting. First, the EU lower geopotentials seems to continue, and the Canada ridging moves further north, replaced by negative departures. Both weeks, especially week 4, have some features that slightly suggest MJO really moving towards phase 5. But allot of this is still open for late April.

A look at Europe. After a persistent “death ridge” in March, a pattern reversal looks to be unfolding. Weakened blocking will move out, over Atlantic, starting to support more of a zonal oriented flow. Overall lower monthly geopotential heights over a continent, mean troughs persistence, with weak or absent ridging in between.

With more troughs and less ridging, its normal to expect anomalous rainfall. Looking at CFS, it clearly confirms it.

Looking at SEEVCC model, which is actually “based on dynamical downscaling of ECMWF seasonal forecast, using a regional atmosphere-ocean coupled model”. It too has the same idea of anomalous rainfall, especially in Central Europe. Now, compared to the CFS, there are some differences, especially over the Balkan region and SE Europe. This is likely due to a different model systems, higher terrain resolution, and also because the SEEVCC model was calculated in March 1st, while CFS is latest. But the idea generally stays the same.

Temperature wise, these two have a slightly different opinion. CFS has average to cooler temperatures over western to middle and northern Europe, where it is also forecasting the main trough activity. Now the reason behind the positive anomaly over to the east is, atleast in my opinion, mainly because of the deeper trough over western Europe, meaning that western to middle Europe is situated more over the back side and the core of the troughs, while more to the east, the SW-erly jet stream advecting warm temperatures into south-eastern Europe.

SEEVCC also has the idea of above average temperatures, not so east and more over Central Europe. Given that it was made on March 1st, the lastest run will show the main positive anomalies to be more to the east.

This is how CFS looked like with March 1st to 10th initial conditions. The positive anomaly was more to the west and northward.

 

Summary: Overall we are quite in agreement with what CFS and SEEVCC are offering. April should be quite normal temperature wise, with above average temperatures possible from central towards east Europe especially later in the month, and normal, maybe slightly below average over some parts of western Europe.

Precipitation anomalies seem to be mostly normal to slightly above average over most of Europe, especially over central Europe, but with complex terrain, precipitation anomalies can differ greatly on a small scale!

A quite dynamical April seem to be in store, like April should look like in Europe. This also the time of year, when winter is retreating towards north and warmth slowly progresses from the south. So the occasional clashes contribute to the overall dynamical patterns and the weather.

Prepared by:
Andrej Flis
Marko Korosec


Tornadoes and very large hail across NE TX becoming likely today!

Robust setup once again over TX today with a slight eastward progressing on the system. Conditons are coming together for another round of severe storms over NE TX where instability, shear/SREH will be maximized. An OFB moving from SE OK southwards should interact with a coming front from the west across NE TX.

SPC issued a large SLGT risk for these areas across SE OK/NE TX and parts of LA/AR while another SLGT risk was issued for IL/IN/SW OH and KY…

10% area for tornadoes in NE TX and 30% hatched for large hail…

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1125 AM CDT TUE APR 03 2012

VALID 031630Z – 041200Z

…THERE IS A SLGT RISK OF SVR TSTMS TODAY AND TONIGHT FROM PARTS OF THE SRN PLAINS INTO LOWER MS VALLEY…

…THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT ACROSS PORTIONS OF THE OH VALLEY…

..SYNOPSIS

MID AND UPPER-LEVEL LOW OVER ERN NM WILL PROGRESS SLOWLY EWD THIS PERIOD IN RESPONSE TO ONSHORE DEVELOPMENT OF AN UPSTREAM TROUGH INTO THE PACIFIC NW. MORNING WATER VAPOR IMAGERY SHOWS A VORTICITY MAXIMUM PIVOTING AROUND THE UPPER LOW ACROSS WRN TX WITH THIS FEATURE LIFTING NEWD ACROSS PORTIONS OF OK/KS TODAY INTO TONIGHT. ELSEWHERE…AN ELONGATED VORTICITY MAXIMUM FROM THE OZARKS TO CNTRL GULF COAST WILL CONTINUE EWD/NEWD WITHIN INCREASINGLY CONFLUENT FLOW REGIME IN PLACE ACROSS THE ERN THIRD OF THE NATION.

IN THE LOW LEVELS…SURFACE CYCLONE OVER NRN IL WILL DEVELOP EWD ACROSS IND TODAY IN CONJUNCTION WITH NRN EXTENSION OF ELONGATED VORTICITY MAXIMUM MENTIONED ABOVE. THIS LOW WILL BE TRAILED BY A COLD FRONT WHICH WILL SETTLE SWD THROUGH THE MID MS VALLEY/OZARKS. THE WRN EXTENSION OF THIS BOUNDARY ACROSS SRN KS WILL REMAIN MORE QUASI-STATIONARY IN RESPONSE TO A WEAK SURFACE LOW DEVELOPING FROM NWRN TX INTO S-CNTRL KS. FARTHER S…A PACIFIC FRONT WILL MOVE SLOWLY EWD FROM W-CNTRL INTO CNTRL TX…BOUNDED ON THE N BY A W-E ORIENTED OUTFLOW BOUNDARY STRETCHED ACROSS NRN PARTS OF TX/LA.

..SRN PLAINS INTO LOWER MS VALLEY TODAY INTO TONIGHT

A N-S BAND OF STRONG-SEVERE…ELEVATED TSTMS HAS EVOLVED THIS MORNING OVER N-CNTRL TX/S-CNTRL OK IN RESPONSE TO INCREASED FORCING FOR ASCENT ATTENDANT TO VORTICITY MAXIMUM PIVOTING AROUND NM UPPER LOW. 12Z FWD SOUNDING SHOWED A MOIST BOUNDARY LAYER BENEATH STEEP MIDLEVEL LAPSE RATES YIELDING MUCAPE OF 2000-2500 J/KG. GIVEN THE PRESENCE OF 40-50+ KT OF EFFECTIVE BULK SHEAR…EMBEDDED SUPERCELL STRUCTURES WILL BE POSSIBLE WITH AN ASSOCIATED RISK FOR LARGE HAIL.

BREAKS IN THE CLOUDS ACROSS NRN/CNTRL TX SHOULD ALLOW FOR SUFFICIENT BOUNDARY LAYER HEATING SUCH THAT ONGOING STORMS WILL BECOME PROGRESSIVELY SURFACE-BASED BY AFTERNOON…WITH ADDITIONAL STORMS POSSIBLE ALONG AND AHEAD OF TRAILING PACIFIC FRONT. THE COMBINATION OF A MOIST AND MODERATELY UNSTABLE AIR MASS /I.E. AFTERNOON MLCAPE OF 1000-2500 J PER KG/ AND 40-60 KT OF DEEP-LAYER SHEAR ORIENTED LARGELY ORTHOGONAL TO THE PACIFIC FRONT WILL SUPPORT SUPERCELLS CAPABLE OF LARGE HAIL AND DAMAGING WIND GUSTS. A FEW TORNADOES ARE ALSO POSSIBLE /ESPECIALLY ACROSS PARTS OF N-CNTRL AND NERN TX/ GIVEN MODESTLY STRONG LOW-LEVEL FLOW AND PRE-EXISTING OUTFLOW BOUNDARIES WHICH WILL LOCALLY ENHANCE LOW-LEVEL SHEAR.

ELSEWHERE…STORMS WILL LIKELY INCREASE IN COVERAGE AND INTENSITY TODAY ALONG OUTFLOW BOUNDARY/GRAVITY WAVE SURGING EWD/SEWD INTO W-CNTRL MS…CNTRL/SRN LA AND SERN TX. WHILE VERTICAL SHEAR WILL REMAIN WEAKER THAN POINTS TO THE W…THE PRESENCE OF A MOIST/UNSTABLE INFLOW AIR MASS /REF. 12Z LCH SOUNDING/ WILL SUPPORT
VIGOROUS UPDRAFTS CAPABLE OF DAMAGING WINDS AND PERHAPS SOME HAIL.

..OH VALLEY

12Z ILX SOUNDING SHOWED STEEP MIDLEVEL LAPSE RATES WHICH WILL COMBINE WITH DAYTIME HEATING AND BOUNDARY LAYER DEWPOINTS INCREASING THROUGH THE 50S TO AROUND 60 F TO YIELD AFTERNOON MLCAPE OF 1000-1500 J/KG. INCREASED FORCING FOR ASCENT ASSOCIATED WITH VORTICITY MAXIMUM LIFTING NEWD THROUGH THE MID MS VALLEY…COUPLED
WITH LOW-LEVEL UPLIFT ALONG SURFACE FRONT ARE EXPECTED TO FOSTER SCATTERED TSTMS LATER THIS AFTERNOON ACROSS PORTIONS OF IL/IN. VERTICAL SHEAR WILL REMAIN RELATIVELY WEAK…BUT THE PRESENCE OF STEEP LOW TO MIDLEVEL LAPSE RATES WILL PROMOTE VIGOROUS UPDRAFTS CAPABLE OF DAMAGING WINDS AND SEVERE HAIL. STORMS ARE EXPECTED TO GROW UPSCALE INTO AN MCS WITH AN ASSOCIATED WIND/HAIL THREAT SPREADING SEWD INTO PARTS OF KY TONIGHT.

..SERN U.S

REMNANT MCV OVER THE FL PNHDL…HEATING ALONG THE HIGH TERRAIN OF THE CNTRL/SRN APPALACHIANS…AND WARM FRONT SLOWLY LIFTING NWD THROUGH THE PIEDMONT AND COASTAL PLAINS WILL ALL SERVE AS FOCI FOR STRONG-MARGINALLY SEVERE TSTM DEVELOPMENT THIS AFTERNOON INTO EVENING. THE PRIMARY HAZARD WILL BE LOCALLY STRONG WIND GUSTS…THOUGH SOME HAIL IS POSSIBLE.

..MEAD/GARNER.. 04/03/2012

Stay tuned!