Severe Weather Targets the Mississippi Valley Today

There is a risk of severe weather this afternoon for states around the Mississippi Valley. This comes as a frontal boundary sags southward and a dry line is located out west.

This is a sounding valid for 18z tonight, known as 7 pm Central time. When you get the dashed line to the right of the soldi blue line, that is when you develop instability. As you can see, there is a large gap between the solid line and dashed line, indicating a lot of instability. CAPE shown on the sounding indicates over 3000 j/kg of instability present at that time.
Another thing seen on the sounding is something called 'ConvT', which appears to indicate the temperature when air will rise to produce thunderstorms. To figure out the surface temperature, I use 28 degrees Celsius, as the solid temperature line is in that 25-30 Celsius area closest to the bottom of the image. Converting 28 Celsius to Fahrenheit results in a temperature of 82.4 degrees F, a good 2 degrees above the ConvT of 80.4 F.
A couple final indices: The Hail index shows hail of 1.5 inches is possible. The hail index is the first parameter in the 4th column labeled 'Hail'. The Supercell Potential parameter, 3rd result in the 2nd column, indicates a 60% chance of a supercell if convection were to develop (which it will).

I don't blame you at all if you don't understand this- I just started getting the gist of it recently after a lot of researching and learning, so my apologies if I am confusing you.
In short, thunderstorms, with a fair chance of becoming supercells, are possible today.

-Andrew

2012-2013 Preliminary Winter Forecast

Hello everyone and here is the long-awaited 2012-2013 Preliminary Winter Forecast.
I have to say, I don't have too much information to share as a lot of pieces are too far out, so this is more of an examination of the ENSO conditions.

This past winter we were in a fake La Nina. It had a La Nina, but with El Nino weather conditions resulting. This summer, we are expected to have a neutral ENSO condition, and by this winter we may even have a slight El Nino. Here's a forecast for DJF (December, January, February) 2012-2013 off the Scripps ENSO Model.

The Scripps Model is forecasting a east-Based El Nino. There is indeed a difference between west based and east based. However, we won't dig into that because it is too far out to tell at this point.
Here's the average precipitation and temperature (respectively) results from weak El Ninos.

A weak El Nino typically brings slightly below average temperatures to the country, while bringing more precipitation to the East Coast and below normal rainfall for the Southeast.

Because it is so far out and I don't have too much to work with, here is what I will say:
•Weak El Nino likely
•Probably more precipitation for the East Coast

-Andrew

Severe Weather Risk for Today, March 30

The Storm Prediction Center has outlined two severe weather risk areas today- one in the Ohio Valley and the other in the South Plains.

The Ohio Valley severe weather risk will be the result of a convective system currently moving east across Illinois. As the system gets into the Ohio Valley, instability of up to 2000 j/kg will be available, making for a situation that could sustain some mainly hail-producing severe storms.

The South Plains severe weather risk is positioned in a way that tells me it may be a linear formation. A system will eject eastward and bump against a dry line in central Texas. This will initiate some strong severe storms that will have a mainly hail-producing risk.

Keep up to date with the latest weather developments on The Weather Centre's Facebook Page.

-Andrew

Storm Prediction Center Outlines Long Range Severe Weather Risk

The Storm Prediction Center has outlined a risk of severe weather for 4 days out in the Southern Plains. I say 4 days out, because 'Day 1' is today, 'Day 2' is tomorrow, etc.

The perpetrator for this severe weather will involve a dry line. This dry line will be stationed in central Texas. As the warm air is drawn north by the storm system located in Wisconsin, the dry line will quickly accumulate a dew point gradient. When the cold front out to the west intercepts this gradient, showers and thunderstorms should be quick to form in Arkansas, Louisiana, and probably some more discrete, severe storm cells out ahead of the system.
As the storm system moves east, wind shearing will increase to a good 60 knots, easily sustainable for tornadoes. This shearing will be accompanied by at least 1000 j/kg of instability. The combination will probably make for some discrete super cells in due time.
There does look to be a fairly weak cap over the area, about 100 -j/kg. This should be easily broken by the storm system.
As the system makes its way eastward, it will try to attain a negative tilt. However, based on the latest GFS, that is possible, not confident. The GFS has the storm take on a neutral/slight negative tilt when it is in the area being monitored for severe weather.

-Andrew

2012 Atlantic Hurricane Season Forecast

Hello everyone, I'm here to present to you the 2012 Atlantic Hurricane Forecast.

Let's get right to it and look at something called the TNA. The Tropical North Atlantic index, or TNA, is based on looking at sea surface temperatures (SST). In areas of above normal SST's, the TNA will be positive. In areas of below normal SST's, the TNA will correspond negatively.

Past TNA

Here's the total past TNA recorded values. As you can see, the majority of 1981-1997 was in a general cooler phase, while 1998-current has been a mainly warmer phase. This does raise questions on if global warming has played a role in this, but that is not nearly what this forecast is on.
Notice how strongly positive the TNA was from 2009 to about 2011. Here's a brief analysis concerning those hurricane seasons.

•2009- Below Average, El Nino.
•2010- Above Average, Neutral/La Nina
•2011- Above Average, La Nina

The reason this is significant is because El Ninos tend to reduce hurricane activity in the region, while La Ninas can strengthen Atlantic tropical activity. The TNA and La Nina combined in 2010 to produce the 3rd most active hurricane season on record.

This attention to the ENSO (La Nina/El Nino) conditions brings us to the question of which condition will we have this hurricane season.
At the moment, we are in a neutral ENSO state, pretty much meaning the 'silver lining' between an El Nino or La Nina. This, to me, means that the effects of the ENSO will not be a real factor, because another way neutral ENSO can be interpreted as is a very weak La Nina/El Nino, although this view point can lead to more issues than solutions with understanding.

Here's the latest SST anomalies for the Caribbean and Gulf of Mexico. While the Caribbean is not too impressive, check out how warm the Gulf of Mexico is! Many areas are over 2 degrees above normal. While that may not seem like a lot, it may have some potentially catastrophic effects on any tropical activity that forms in the Gulf. If a cyclone does form, it will have all of that warm water to use to strengthen.

All of that said, here's my forecast.

I am expecting an above normal hurricane season with a strong positive TNA combined with very weak, if nonexistent ENSO effects. A very warm Gulf also adds to the forecast. I put the chance for a landfalling US hurricane at 65%, because we are overdue (which honestly adds nothing to where hurricanes go), but mainly due to the very warm Gulf of Mexico.

-Andrew

Winter's Final Gasp of Snow to Fall in the Northeast

0z GFS Snowfall Forecast

Winter's potentially final snowfall will fall in the Northeast tomorrow, with a general 1-4 inches of snow expected across the region.
This snow will fall as a storm system makes its way eastward across the US and manages to pass across some moisture that meets up with some cold air to make snowfall for the Northeast. Again, nothing major, just a few inches to satisfy those in the Northeast that got very little snow over the course of this past 'winter'.

-Andrew

Remember-

Remember that the 2012 Atlantic Hurricane Season Forecast will be issued today at 12:00 PM CDT,
and the 2012-2013 Preliminary Winter Forecast will be issued tomorrow at 12:00 PM CDT.

I sincerely apologize for the delay instead of not posting it yesterday, when it was scheduled. It was not my intention to have it be delayed.

-Andrew

Glance at the Lezak Recurring Cycle

A system I like to use is the Lezak Recurring Cycle, or LRC. Basically, it indicates a cycle starts in early winter that will cycle over and over again between a 45-60 day period. It can range from a very wet pattern to multiple drought-like weather scenes in the cycle. The cycle is different every year, and the time it takes to make a full cycle varies, but typically falls between 45-60 days.

The LRC was present in the winter when the warm temperatures kept cycling over and over again through the winter months. Now, with records broken in the last couple weeks, it has definitely been proven to be part of the LRC.



Now, if we follow the LRC through the rest of spring, here is what I believe we will come up with:
•A continuation of very warm, if not record breaking, temperatures.
•Many more opportunities for severe weather, mainly focused in the Southern Plains into the Ohio Valley.
•Speed Bumps of cooler air, soon filtered back into warmer spells.

Now, the reason I am concerned for more severe weather opportunities is because the deep, negative tilted storm systems that recently tore up the Plains are embedded in the LRC, meaning that, in due time, they will come back again- possibly with some more vengeance as spring gets fully underway.

Another interesting piece- Gary Lezak, who created the LRC, recently wrote a comparison to January 17 and March 2 in terms of the tornado events.
Using those two dates on a 45-50 day cycle, it would be reasonable to think that the next potentially major outbreak would fall on a Mid April timeframe.

Here's a link to the Accuweather Forums' own LRC thread, containing a lot of the information I use to learn about the LRC.

-Andrew

**UPDATED** Spring-Summer Tornado Forecast 2012

Hello everyone, I'm here to present to you the Updated Spring-Summer Tornado forecast.
Already this year, there have been deaths and horrible occurrences of very strong tornadoes. In a very similar situation where fall can determine winter, I believe late winter can determine spring. If this is true, we are in for a very rough ride.

The chart above shows average tornado reports through the first half of the year. Also superimposed are the long range trend for tornadoes as well as 2012's tornado reports. As you can see, the tornado season of 2012 is already way above the average trend, and it's not even April!

I believe that warm weather will continue to flourish this spring and summer and make for above average temperatures. This tells me that a ridge will be in place over the East US. If that happens, storm systems may sweep south through the Southwest and eject into Texas and make for some severe weather. I also see the potential for storm systems to eject into the North Plains and hit the Plains and Midwest with some severe weather when warm air is not overwhelming the country.

Here's my outlook for the rest of the tornado season. I feel that an already warmer-than normal Gulf of Mexico along with a more active jet stream helped in part with the cool Upper Level Lows that will charge through the Southwest and into the Plains will greatly contribute to a sizable tornado threat, mainly centered in the Southern Plains and into parts of the Ohio Valley and southern Midwest.

-Andrew

Severe Weather Possible in Midwest Today

Overview of Severe Weather Threat

Hail Outlook

Tornado Outlook

Damaging Wind Outlook

The Storm Prediction Center has outlined parts of the Midwest for a slight risk of severe weather today.
The main threat today appears to be damaging wind and hail, but the tornado risk is somewhat elevated and may need to be watched.

This comes as a storm system moves eastward from the Plains and brings with it some warm and humid air. The extent and power of this air appears to be centered in Illinois, Missouri and Iowa.

Here's an image projecting the calibrated potential for a severe thunderstorm, valid around 6-7 pm CDT this evening. If we use this to determine the area of greatest risk, it is quite easy to see that the Illinois/Iowa border is at the greatest risk for severe weather today.

'Like' our Facebook Page for updates not seen here on the blog at http://www.facebook.com/TheWeatherCentre

-Andrew

2012 Summer Forecast

Hello everyone, this is the 2012 Summer Forecast from The Weather Centre.
The big topic this winter has been the La Nina that never was. It was present and shown in the oceans, but the effects on land were similar to that of an El Nino for some places. This phenomenon is commonly referred to as a La Nino.
Anyhow, you will be glad to know that the La Nina appears to finally be giving way, and the summer months of this year look to be in a neutral ENSO state. So, what does this mean?

Well, to be quite frank, in my opinion it means very little. While there is indeed a spectrum of the ENSO indices that includes a neutral region, keep in mind that a La Nina and El Nino are extremes on that spectrum and neutral territory can be classified as a very weak La Nina or El Nino. Because of how weak it is, other indices like the NAO, MJO etc. can override that neutral ENSO phase.

Here's a forecast for the summer months (June, July, August (JJA)) from the ECCA long range ensembles.

Precipitation Forecast

Temperature Forecast

Areas of darker shades indicate 'skill areas', where the ensembles are more confident in that forecast for that area.
The ECCA is projecting a mainly warm summer, with only parts of the West Coast and south Florida getting in on some cooler weather. I feel that this forecast will probably verify. A La Nina typically brings about cool temperatures. With that La Nina fading away, temperatures would be expected to remain normal. However, counting in the extreme warmth we have been seeing across the country in recent weeks, I could see this being a sign that summer will also be warmer than normal.
More abundant precipitation is confined to the Plains and Midwest than the rest of the country. I feel like this depends on the jet stream. If the country is to be warm, the jet stream would probably be zonal at some point, going along the US/Canada border. This would bring the storm systems across the border as well. However, at the same time, storm systems would hit the Southwest, eject into the South Plains, and produce high-precipitation events across the Plains and Midwest. This is a scenario that is certainly on the table.
Now, the forecasts I have made aren't exactly having the highest confidence and are biased off of the ECCA model. That said, here is my forecast for Summer 2012.

Precipitation Forecast

Temperature Forecast (Skill area in darker shades).

-Andrew

Severe Weather Discussion for Tomorrow, March 27

Probability of Severe Weather

Probability of any severe weather events

A slight risk has been issued by the Storm Prediction Center for tomorrow, March 27.

This risk of severe weather is probably going to verify, with a sturdy 1000 j/kg of instability combined with 50 knots of veering winds to make for some large hail in the stronger storm cells. I'm not looking at a huge severe weather event- probably along the lines of several isolated storm cells over a broad area with a few in the realm of severe weather.

As a warm front quickly followed by a cold front progresses east, this should be the instigator for any storm cells that may form. Imposing the frontal systems against instability and shearing makes me think that this event will be supported by the veering winds/shearing, which may not come through for all of the storm cells in question.

-Andrew

Severe Weather Discussion for Today, March 26

Overall Threat

Hail Risk

Tornado Threat

Damaging Wind Threat

The Storm Prediction Center has outlined a risk for severe weather today, March 26, in the Northern Plains.

A negatively tilted storm system looks to eject into the North Plains today. As it does so, some thunderstorms are likely to develop in the midst of modest instability values around 1000 j/kg.  It looks like there will be ample hail opportunities with around 40 knots of veering wind from the surface to the mid levels of the atmosphere. This does indicate the likelihood of the stronger storms in this event to be hail producers.

Infrared imagery indicates a plume of clouds moving into the Northern Plains, where the storm system is expected to be. As this earlier cloud cover comes into the area, and with its proximity from the Gulf of Mexico, I find this severe threat to be rather low and it may be slightly over-calculated from my vantage point.

-Andrew

Storm Prediction Center issues Slight Risk for March 27

The Storm Prediction Center has issued a slight risk of severe weather for parts of the Lower Great Lakes and Midwest regions for March 27.

The Storm Prediction Center highlights a combined 1000-1500 j/kg of instability with veering flow aloft to create a risk for some strong and potentially rotating thunderstorms. More recent returns of the 12z GFS suggest flow veering at 50 knots, increasing the potential for some severe thunderstorms.

Here's the latest 2:00 PM central run of the TRIAD Tornado Model, updated to fix errors.

-Andrew

CFS v2 Projects Below Normal Temperatures

Week 3 (top) and week 4 (bottom) forecasts are in from the CFS v2, and after nailing the record breaking warmth, the CFS is indicating that temperatures may actually become below normal towards mid to late April.

This comes as a ridge of high pressure may come into the Gulf of Alaska, as told in this morning's post.

-Andrew

Record-Breaking Warmth Unlikely as Ridge Fills Gulf of Alaska

The latest GFS 500mb analogue forecast is indicating that another spell of record-breaking warmth is unlikely as a ridge of high pressure moves into the Gulf of Alaska (GOA).

This past winter, warm spells would occur with a low pressure system present in the Gulf of Alaska. That low in the GOA is a traditional signal of a warm spell forthcoming in the US.

With our most recent record-breaking warmth, there was indeed a strong low pressure system in the Gulf of Alaska. However, with a ridge now poised to take over, it can be expected that temperatures much closer to average will be prevalent. I'm not saying they will be average, because I am getting some signals that they will be warmer than normal, but temperatures will be closer to average than record breaking.

-Andrew

Notice

The computer is back up and running at full power. However, because it has been through much more than a computer should go through in the last 48 hours, there will be no updates for the remainder of the day. Do, however, expect thorough weather discussions to come back tomorrow.
All long range forecast release times remain on track.

-Andrew

Notice #2

Update on software issue: I am still working as hard as I can, but things are looking a little too grim for my liking. A repair of the disk does not appear to be successful. More updates as the situation progresses.

Andrew

Notice

This is about as horrible of timing as things can get.
The normal computer I use may have suddenly died out. I am working hard to try and correct the problem, but this does have potential to delay the long range forecast releases. At this time, however, there is no delay.

I will provide updates every so often, but this is the best I have for now.
My sincerest apologies,
-Andrew

Long Range Forecast Release Dates

Hey everyone, it's been a while since I touched on the long range forecasts in honor of 500,000 views and 100 models and ensembles on our Weather Models page, and I feel like this has to be addressed.

It's about time you all got a few gifts for checking out and commenting on here, which I greatly appreciate. So here's what will be coming up next week:
(All times are CDT and subject to minor changes.)

-Monday, March 26: 2012 Summer Forecast (3:30 pm)
-Tuesday, March 27: Updated Spring-Summer Tornado Forecast (12:00 pm)
-Wednesday, March 28: Atlantic Hurricane Forecast (12:00 pm)
-Friday, March 30: 2012-2013 Preliminary Forecast (12:00 pm)

-Andrew

Signs that Potentially Record Breaking Warmth May Continue

If there's one thing to be learned this winter, it is this: Many models look like they're just taking stabs in the dark. And this was true, especially for respected models like the ECMWF and GFS, to those lesser-used JMA, CMC, NOGAPS models.
But there were a select couple of correct models. The model shown above is the NAEFS Ensembles, or the North American Ensemble Forecast System. This model was the lighthouse in this sea of model uncertainty. It nailed all predictions for a warm winter. That said, I am investing confidence in it yet again to formulate this forecast.

Using the NAEFS, the period between the next 8 days and next 14 days (Days 8-14) tells of widespread areas with temperatures that are at a 90%+ probability for being above the normal temperature. This is most common in the Plains and Canada, with a little cooler forecast to the east.
Now, I am a little hesitant to believe this, because the atmospheric feature that has been causing this record-breaking heat is now moving away. It is a mega-ridge of high pressure, and it is slowly moving to the east, offshore the US. This means more storm systems will be able to pass through that area and therefore create a more progressive temperature pattern of cold fronts and warm fronts. Or so it would be thought.
While the NAEFS is not a forecaster for hourly SLP (sea level pressure (low areas are low pressure systems, high areas of SLP are high pressure areas)), using long range precipitation accumulations, I can determine that the storm track looks to be suppressed south according to the NAEFS. This would indeed allow a buildup of air to occur in the North Tier of the US, and this air would likely be warm, using the temperature forecast.

-Andrew

Temperatures to Moderate in Next Several Days

WB013_MAXTEMP_WEEKDEP_E_2.png

Temperatures will be moderating in the next several days, stopping the record-breaking heat in its tracks. The image above shows maximum temperature departures (maximum or minimum temperatures) for March 27 to April 2. As you can see, temperatures may even be below normal in the Ohio Valley, with the warmth stationed in the North Plains and Northwest parts of the US.
This cool down comes as the mega-ridge of high pressure will be shoved offshore, bringing the warm weather with it and putting jackets and jeans back in style.

-Andrew

Rough Night Ahead for Texas, Oklahoma

Here's the latest forecast off Norman, Oklahoma's National Weather Service Office WRF Model. It is showing something I certainly would not want to be in, with rampant bowing segments and intense storm cells. Judging by this image (which is valid at 5:15 PM CDT), this is probably a bit overdone, but nonetheless sending a warning message which should validate, even if the image should not.
The storms currently in progress have a good 1000-2000 j/kg of instability to work with, which should sustain any storms that do develop. But then here's the thing that could push the storms to the next level- frontogenesis.

Current Surface Frontogenesis

The whole concept of watching for elevated levels of frontogenesis is that it helps severe storms. Frontogenesis means the making of a frontal boundary, and we weather folk know that storms favor frontal boundaries to form and become the strongest along a frontal boundary. You know there is a frontal boundary present when there are elevated levels of frontogenesis, and in this case, the levels are sky-high, only adding to the case to enhance severe storms.

My Thoughts include that these storms will move into southeast Texas, where more instability will be available. As the sun sets, daytime heating will take a big punch out of storms, but if there remains strong frontogenesis and fair lifting and instability mechanisms, the storms could certainly continue along through the night.

-Andrew

As Promised...

As promised, something big will be happening with 100 models and ensembles on our Models page coinciding with 500,000 views on the blog. And now I'm happy to say that ALL long range forecasts on the poll on the right will be published! Dates will be announced soon.
Also, updates concerning the severe storms in the Plains will be coming this afternoon.

Moderate Risk for Severe Thunderstorms Today

Hail Outlook

Tornado Outlook

Damaging Wind outlook

The Storm Prediction Center has issued a moderate risk for severe weather on account of the risk for damaging winds today, and it is a very valid risk. Take a look at this short term forecast from the Marquette, Michigan's WRF model.

This WRF model is predicting scattered storm cells to come together to form a strong squall line. This WRF is one of many WRF's run at different NWS forecasting offices. Just taking a glance at some other WRF model runs tells me that it may be even worse than this, with the Norman, Oklahoma WRF forecasting extreme storm cells in the TX/OK region.

Here's the Storm Prediction Center's Public Severe Weather Outlook

PUBLIC SEVERE WEATHER OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0321 AM CDT MON MAR 19 2012
...WIDESPREAD SEVERE THUNDERSTORMS EXPECTED OVER PARTS OF THE
SOUTHERN PLAINS TODAY AND TONIGHT...
THE NWS STORM PREDICTION CENTER IN NORMAN OK IS FORECASTING THE
DEVELOPMENT OF WIDESPREAD DAMAGING WINDS...VERY LARGE HAIL AND
TORNADOES OVER PARTS OF THE SOUTHERN PLAINS TODAY AND TONIGHT.
THE AREAS MOST LIKELY TO EXPERIENCE THIS ACTIVITY INCLUDE
FAR SOUTHWEST ARKANSAS
SOUTHEAST OKLAHOMA
CENTRAL INTO NORTHEAST TEXAS
ELSEWHERE...SEVERE STORMS ARE ALSO POSSIBLE FROM THE MID-MISSOURI
VALLEY TO THE TEXAS GULF COAST.
A POWERFUL UPPER-LEVEL STORM SYSTEM OVER THE INTER-MOUNTAIN WEST
WILL SHIFT EASTWARD INTO THE GREAT PLAINS TODAY IN CONJUNCTION WITH
A SURFACE COLD FRONT. A LINE OF SEVERE THUNDERSTORMS HAS DEVELOPED
EARLY THIS MORNING AHEAD OF THE COLD FRONT OVER WESTERN PORTIONS OF
TEXAS AND OKLAHOMA. THESE STORMS ARE EXPECTED TO CONTINUE THROUGH
THE MORNING ACROSS PARTS OF OKLAHOMA AND NORTHERN/WESTERN TEXAS WITH
ASSOCIATED THREATS FOR DAMAGING WINDS AND LARGE HAIL.
TO THE SOUTH OF THIS INITIAL THUNDERSTORM ACTIVITY...THE INTERACTION
OF MOIST AND MODERATELY UNSTABLE AIR MASS WITH STRONG...LOW AND
UPPER-LEVEL JET STREAM WINDS WILL CREATE AN ENVIRONMENT FAVORABLE
FOR INTENSE THUNDERSTORMS...INCLUDING SUPERCELLS...ACROSS PARTS OF
CENTRAL AND NORTHERN TEXAS INTO SOUTHEAST OKLAHOMA LATER TODAY.
LATEST WEATHER MODEL DATA INDICATE THAT MULTIPLE WAVES OF
THUNDERSTORMS WILL BE POSSIBLE FROM THIS AFTERNOON THROUGH TONIGHT
ACROSS THIS GEOGRAPHICAL AREA. VERY LARGE HAIL TO BASEBALL SIZE OR
LARGER AND WIDESPREAD DAMAGING WINDS APPEAR LIKELY...ALONG WITH THE
POTENTIAL FOR A FEW TORNADOES.
STATE AND LOCAL EMERGENCY MANAGERS ARE MONITORING THIS DEVELOPING
SITUATION. THOSE IN THE THREATENED AREA ARE URGED TO REVIEW SEVERE
WEATHER SAFETY RULES AND TO LISTEN TO RADIO...TELEVISION...AND NOAA
WEATHER RADIO FOR POSSIBLE WATCHES...WARNINGS...AND STATEMENTS LATER
TODAY.

-Andrew

100 Models and Ensembles Reached!

We have officially reached 100 models and ensembles on our Weather Models page!
This does indeed call for something big. I have it figured out, and you will find out in a few days.

March Severe Weather Events Were Predicted (And How You can Predict Them Too)

Potential Jet Stream and Severe Weather Nodes (Made March 3)

Set-up predicted for March (prediction made March 3)

The severe weather that ravaged the country in the last couple weeks of March had been advised on earlier in the month.
In this post from March 3, I declared that there would be a risk for some severe weather outbreaks as the infamous Alaskan Vortex shifted into the Gulf of Alaska. Lo and behold, my predictions came through in the situations I had anticipated.

Now that these predictions have come through, I want to share this with you to give you some advice on how to know if your area could get hit with some severe weather.
The thing I look for in this situation was a deep low pressure in Alaska. If that is there, a ridge should form in the East US, storm systems will come onshore the West Coast, and the rest will follow.
While I could not have anticipated the exact timing and severity of the severe weather events, this is just something that I thought should be shared to give others an idea of when severe weather may hit the country.

Special TRIAD Run Downgrades Tornado Threat

The TRIAD Tornado Model has downgraded the tornado threat today to a red maximum, which means the TRIAD is expecting a few isolated tornadoes, with the potential for a strong tornado.
I realize that this is not the most ideal set-up for tornadoes, but I am surprised the Storm Prediction Center did not issue a moderate risk to be on the safe side. I have been watching shearing, wind convergence, helicity, instability throughout this event and have firmly believed that this would warrant a moderate risk area by the SPC. There remains the potential for them to issue a short-term moderate risk area in the next update today, but I can't say that is too likely at this time.

Some info on this special TRIAD model run:
Model(s) used: SPC SREF Ensembles.
Time run: 9:30 am central.
Confidence: 90%
Potential of upgrading to higher tornado threat: 40%
Potential of downgrading to lower tornado threat: 20%

-Andrew

Notices for March 18, 2012

•A Storm Action Day will remain in effect today, despite the lessened threat than anticipated.
•A Special run of the TRIAD Tornado Model will run at 11:00 AM central time.
•I am surprised that the Storm Prediction Center did not issue a moderate risk, and I believe that the tornado threat is being taken a tad too lightly.

Tornadoes, Severe Storms Possible in South Plains Tomorrow

Confidence: FINAL FORECAST

Here's the new 4:00 PM CDT run of the TRIAD Tornado Model. I have extended the threat north, as well as slightly enhance the threat for north central Texas.
However, while I did use the normal model blend for this TRIAD model run, I mixed in the SPC SREF, which is falling into line with the regular models that are used with the TRIAD model.

As the strong storm system ejects eastward, I expect the dry line to be the focus of severe storm development tomorrow. This dryline should be positioned somewhere in west TX/OK/KS. The dry line will be crucial in this situation, as converging winds will likely get the updrafts going when instability values begin to increase over the dry line. As instability increases, updrafts should begin to form and, judging by forecast hodographs and wind shearing, a couple of these updrafts should have the capability to develop some rotation within these updrafts.
As a screaming jet stream with speeds of 100 knots+ moves over these developing updrafts, it will only increase the level of deep layer shear, also increasing the tornado threat and shifting it south and east with time. I expect to see some tornado touchdowns tomorrow, most likely in the central portions of Texas. I find it entirely possible that some tornadic action could develop farther west in Texas than what is currently progged, but due to the uncertainty of the dry line's position and slight uncertainties in the strongest instabilities in that region, I discouraged the TRIAD from stretching the threat too far west.

Afternoon Bulletins

For clarification, the TRIAD will be run again at its usual time (4:00 PM central) with its usual model blend.
Additionally, a poll will be up shortly asking which long range forecasts you would like me to release in honor of 500,000 views. You will be able to choose more than 1.


-Andrew

Half a Million Views Reached!

Thanks to everyone for helping us reach 500,000 page views!
In honor of this, I am thinking of whipping up a few long range forecasts. What do you think?

-Andrew

Nearly at 500,000 Views!

When The Weather Centre hits 500,000 views, I will be releasing something big in honor of it. Stay tuned!

Special TRIAD Run Positions Tornado Threat in Texas

This specialized 10:30 AM run of the TRIAD Tornado Model indicates that the tornado threat is now biased in Texas. This run is biased off the SPC SREF ensemble members, as well as past trends of the SPC SREF members.
Since this is a specialized run, the regular 4:00 PM central TRIAD model run will go on as planned.

Confidence: 65%
Reason: The SPC SREF index I used to determine the TRIAD output shows wind barbs, and it looks like these winds will be converging into a line that is likely the dry line that will start out these storms. The question is if these storms will start out as individual, discrete storm cells or a linear storm system (squall line). These converging winds will continue to be the base for the tornado threat as per the SPC SREF. This 9z SPC SREF run has dramatically increased the tornado threat for this event.

The reason confidence is so low is because this is a single model and not the regular blend I would prefer to use.

Supercell-Style Pictures from March 16, 2012

Copyright The Weather Centre.
This was a strong storm cell just off the west side of Lake Michigan from this afternoon.