Zitat

---

An El Nino episode was officially and finally declared in the Tropical Pacific as of the last El Nino-Southern Oscillation (ENSO) Advisory from the Climate Prediction Center on March 5, after several months of subsurface warmth that until recently, failed to materialize on the surface and couple with the lower atmosphere. This is the first official El Nino since 2010, and the 5th declared since the new millennium (i.g., 2002-03, 2004-05, 2006-07, 2009-10), each of which were big storm chasing years from what I remember, but we need to take a closer look at the specifics of this El Nino before making any reasonable assumptions on how it will impact spring-summer severe weather/tornadoes.

If you haven't read that CPC advisory, check it out here: http://www.cpc.ncep.noaa.gov/products/an...nsodisc.html178

I'm always keeping an eye on the SST anomaly patterns in the Pacific/Atlantic Oceans, since monthly-to-seasonal climate variability in North America has been the focus of my graduate research for years... and I have to show the striking resemblance of the present SST anomaly pattern in the tropical/subtropical Pacific to one of the characteristic patterns I derived in my dissertation -- I call it the "transitional ENSO mode". The most recent actual SST anomalies are shown at left below, next to the characteristic pattern from my dissertation at right.


What makes this pattern unique is not how the SST anomalies appear right now, but in how they have evolved. Typically, this transitional El Nino mode happens after the El Nino reaches maturity, with neutral or below normal SST anomalies eroding the warmth from east to west across the eastern tropical Pacific. For this 2015 El Nino, however, the positive anomalies materialized at the surface first in the central tropical Pacific (called the Nino 3.4 region), which is very unique. While it is unclear how the El Nino will evolve from here (will it expand across the entire tropical Pacific or remain confined in the Nino 3.4 region, intensify or remain weak, etc.), a majority of dynamical models show the El Nino continuing in at least its present coverage and strength through the summer.


The model ensemble above is from last month, and the figure below from the CPC ENSO advisory shows even greater confidence in the El Nino continuing through the 2015 warm season.


What does this mean for the 2015 storm season? We're planning on releasing a test tornado forecast by state next week for this spring and summer, but based on my initial glance of this SST pattern and comparing it with the characteristic patterns in my dissertation - I'd say generally this will be a late starting storm season, first in Dixie Alley from an active Subtropical Jet Stream, and then an active late April/May in the Southern Plains. Similar ENSO conditions were present during late winter/early spring of 1994, 1995, and 2003, each of which were active seasons in the Panhandle region. While this is only a few years, I wouldn't be surprised if we see some early June tornado outbreaks in the Texas Panhandle this season... but keep in mind this is more speculation and hand waving at this point.

What are your thoughts??

All I know is if there are storms and tornadoes we'll do our best to chase them

---