Monday, March 26, 2012

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).

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.


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.