Tuesday, July 28, 2015

Yes, Big El Nino Brewing But Not All El Ninos Are Alike: 2015 vs 1997

You have probably heard about the BIG EL NINO or SUPER EL NINO or some phrase like that. If not then you will soon enough. Eventually EL NINO will trend on social media by the end of September. You heard it here first.

But hold on. Doesn't Big El Nino mean mild winter?  Not necessarily. See the differences between the last BIG El Nino in July 1997 and July 2015.  Also, notice the differences in the North Atlantic ocean temperatures? This is why the winter 2015-16 outlook is not an "El Nino shoo-in". Not all El Ninos are alike. (See my post on the different El Ninos and what they mean for our weather)

When will we know enough to make an educated assessment on the upcoming winter?  Probably by the end of September. Stay tuned...

Wednesday, July 01, 2015

Record Setting June Rainfall

The persistent pattern featuring frequent rain across the Ohio Valley ramped up into high gear the second half of June. Most points from Columbia, Missouri east into the Mid Atlantic states received between 100 and 400% MORE rainfall than normal this last month.

Parts of northern Ohio had between 10 and 15 inches as a stalled front oscillated back and forth triggering clusters of rain and storms. Cleveland's monthly total was 3rd most in 145 years, most since 1972.  Ft Wayne, Indiana set their all-time June rainfall record with 11.98". It broke the record for the wettest month set in July of 1986! 

Last summer's wet region was centered in the heart of the corn belt.

This summer's wet areas have shifted east into the Ohio Valley including Pennsylvania, Maryland and portions of New Jersey.

Compare the past two summer to the very warm summer of 2012. Dry conditions prevailed with the development of a flash drought across parts of the US. I gave a talk at the Ohio State Weather Symposium on the causes and the conditions that feed that summer's dry pattern.

My POWER POINT from the symposium is here. Check it out.

The average temperatures for July and August in 2012 were certainly influenced by the lack of rainfall. Notice the location of the temperature anomalies.

Temperature anomalies in 2014 were noticeably cooler over the wetter ground in the Corn Belt.

I emphasize that the rainfall or lack thereof was not the primary driver of the patterns in either 2012 or 2014.  It was an enhancer. June temperatures were at or slightly below normal.

Record high temperatures across the Midwest were markedly lower in 2014 vs 2012.

Big question, how will the June rainfall in the Ohio Valley influence the temperatures in the upcoming weeks?

More than likely, we should see a dampening of long stretches of heat in the mid-west, corn belt and Ohio Valley.  July could end up with temperatures at or below average from St. Louis to Cleveland.

Monday, June 08, 2015

Early Summer El Nino Update

More geeky weather talk ahead >>>

The newest updated from the MEI (Multivariate Index) website run by Klaus Wolter shows a significant increase over the last month of +0.61 to +1.57 as of April/May which rates the El Nino in the strong category using a ranking method.  If we look at the top April/May rankings according to Mr. Wolter then then take away the El Nino events that were weakening as of April/May, we are left with the 5 years below. ALL OF THESE YEARS STAYED AT EL NINO LEVELS THROUGH THE END OF THE YEAR.

One important note: Only 1998, 1993, 1992, 1987 and 1983 had HIGHER MEI levels in April/May. 1987 was a only building El Nino. The rest were fading or close to it.

The El Nino is very apparent in the current sea surface temperature anomaly map in the last week of May.

The 2014 El Nino (although not official using the ONI) was considered weak by many meteorologists including myself.  If you assume a weak El Nino for a time last year, this year's much stronger event would be a 2nd year El Nino. Expanding the possible El Nino matches using the MEI TIME SERIES for "double El Nino events" we found two such events:  Late 1991 through 1993 and 1986/87.  A 2nd year El Nino has the advantage of an ocean already primed from the previous one.

It's not an exact match but comparing these two years to 2014-15 gives us an idea of a possible El Nino outcome.  Remember that this year's El Nino is developing much earlier. Most El Nino's develop in late summer and fall.

By examining the MEI, assuming a building El Nino, a double El Nino event (last year was weak) and a very high April/May MEI, a good match so far is the 1986-87 event.

What were the bi-monthly overlapping sea surface temperature anomalies starting in April through the end of 1987?  Notice the cooler water in the western Pacific near Australia which is necessary for the development of a strong El Nino according to the Australian Bureau of Meteorology.

Watch how the lower temperature areas warm by the end of the year (lower two maps below) and the warmest regions start to cool a bit as the El Nino started to fade by year's end.

How about this year's event?  The water off the coast of Australia (circled in red) is starting to cool comparing April 1st to may 27th but not at the level of the 1986-87 event...yet.

This El Nino continues to strengthen much earlier than other El Ninos. We continue to watch the water temperatures in the western Pacific near Australia as they cool.  How cool will they get? Will the El Nino peak in late Fall then taper off?

Models are strongly hinting at this...

Our summer outlook took much of this into account. Check it out here on my weather blog post from early May. 

BIGGER QUESTION, how will this El Nino impact winter?  Too early to call. More on this in August!

Monday, June 01, 2015

How Much Rain Actually Fell Across Northern Ohio?

If we took all of the rain this past weekend across northern Ohio and calculated the volume in gallons, how much would we have?

First, I eyeballed the area across northern Ohio that received roughly 3/4" of rain by late Sunday morning. The area is 16,000 square kilometers (6200 square miles)...

The area that received roughly 1.5" of rain was around 2000 square miles...

The smaller area that received at least 2.5" wasa little under 400 square miles.

Convert the "square miles" to "square feet" for each area: 

6300 square miles = 173 BILLION square feet  (3/4" rain)
2000 square miles = 56 BILLION square feet (1.5" rain)
400 square miles = 11 BILLION square feet (2.5" rain)

First, I calculated the volume of water for the area that received 3/4" of rain:

Volume = length x width x height  or AREA x height

VOLUME 1 = 173 BILLION square feet x 3/4" rainfall (0.0625 ft) =
roughly 11 BILLION cubic feet

In order to not double count volumes, I subtracted the starting 3/4" from the second 1.5" to get the HEIGHT for the volume calculation of the second area

VOLUME 2 = 56 BILLION square feet x (1.5" - 3/4") rainfall or 0.0625 ft = 
roughly 3.5 BILLION cubic feet

I subtracted second 1.5" from the third 2.5" to get the HEIGHT from the volume of the third area.

VOLUME 3 = 11 BILLION square feet x (2.5" - 1.5") rainfall or 0.083 ft =

roughly 886 MILLION cubic feet

Add the volumes together, we get: ~15.2 BILLION cubic feet


That's alot of water!

Monday, May 25, 2015

Short Range Computer Projection vs Actual Radar

Its Memorial Day here at the station. I remember my dad, grandfather, uncle, brother-in-law who served in our Armed Forces over the generations.

I've been watching a few showers popping up on radar.  Nothing heavy, nothing widespread.  One helpful tool we use in determining where and when precipitation develops is the newly operational HRRR model (short for High Resolution Rapid Refresh).  In essence, this model assimilates 3 km radar data into it calculation each hour.  So rather than wait a full 6 hours until the next set of model outputs, the HRRR runs a NEW output every 60 minutes taking into account the ew radar information.

This morning, I ran a little experiment to see how accurate the HRRR was in determining the light showers it was showing for 9AM.  The NWS Cleveland radar was down for repairs so this was a perfect opportunity to see how this would affect the output.

Here is the HRRR Output each hour starting with the 5z (1am) run and concluding with the 11z (7am) run.  So the 5z run is 8 hours from 9am.  The 11z run is 2 hours from 9am.  So each successive model run brings us closer to the 9am target time. 

A light shower west of Cleveland...


By the 8z run, the HRRR started to shift the light shower further west into the main cluster of rain along the Ohio/Indiana border.  By 11z, it had merged with the western rain area.

Here is what the actual radar looked like at 9AM using the TDWR radar in Grafton since the NWS radar was still down as of this writing.  Hardly any precipitation!

Thinking outloud...

*  The HRRR overestimated the development 
*  Unknown whether Cleveland radar downtime had an affect
*  Unknown whether or not TDWR radar data from the FAA is incorporated into HRRR model.

Friday, May 22, 2015

How Does This Early El Nino Start Compare To Others? Implications.

Last year at this time (Spring 2014) the talk of a "Super El Nino" was at the forefront of weather circles. The resultant El Nino later in the year surely didn't fit the hype for a variety of reasons.  This year's close El Nino cousin is a little different.  I believe the "hype" is more warranted this go-around.

Here is a great El Nino animation from NASA showing its evolution.

Using the ONI (Oceanic Nino Index), I logged all El Ninos since the early 1900s.  The ONI is a 3 month overlapping sea surface temperature anomaly index of the Nino 3.4 region, the area used in defining the ENS state.

In determining how different this evolving El Nino is compared to past events, I used the actual NON-OVERLAPPING monthly Nino 3.4 sea surface temperatures anomalies for each early stage El Nino event starting in March and continuing through December. My goal was to see any slight variation in ocean temperature that was smoothed by the 3-month overlapping ONI.  Note: Many of these El Nino events continued into the following year not shown here.

The first chart below shows El Nino events from 1982 to early 2015.

Some key points:  This year's event has started MUCH FASTER and earlier than the historic El Nino events in 1997 and 1982. 

The 1986-87 event peaked in summer then slowly dropped by fall after a similar start.

The current El Nino is well ahead of all of the events from the early 1950s through the late 1970s. Some of these El Ninos were weak. 1965 and 1972 was strong.

The El Ninos of the late 1920s, 30s and 40s were late bloomers showing little sign of El Nino until mid fall.

The early 20th century El Ninos had more erratic evolutions. Even the strong El Nino of 1918 struggled until fall/early winter.

Of all 23 El Ninos I charted, only the El Nino of 1905 had WARMER ocean temperatures in May compared to this year's event. That year peaked at 1.5 in September.

So in summary...

*  El Nino headlines need historical perspective.  Don't be quick to compare this event to the 1997 event per the model projections.

*  The 2015 El Nino is building faster than any El Nino since 1905

* The rapid rise in ENSO 3.4 ocean temperatures this early in spring historically usually means the El Nino will sustain itself through the summer. The major El Ninos of 1997, 82 and 72 started off slower. A big start doesn't necessarily mean 2015 will be another 1997 or 1982.  In fact, the warmth is more centralized. The warmth in '82 and '97 sloshed eastward by summer.

Warmth so far this year has two lobes, one central near dateline and another eastern closer to South America.

* The moderate El Ninos (SST 3/4 between 1.0 and 1.5) in 1987, 72, 65, 57, 30, 25, 23, 18, 05 and 1902 all sustained El Nino status through December per the ENSO 3/4 ocean temperatures.

What does all of this mean for the summer, fall and upcoming winter?

* The next 2-3 months will be critical in determining how this El Nino will impact our (US) weather this summer and especially fall.early winter.  The position of the warmth will be a big factor.

*  How much cool water near Australia relative to the ENSO 4 and 3/4 region temperatures will be HUGE in driving the westerly wind bursts necessary in sloshing more warmth to the east keeping the El Nino machine going.

Next week, we'll dive more into why the COOL WATER NEAR AUSTRALIA is so critical in the development of El Nino

Tuesday, May 12, 2015

Summer Outlook 2015

Lots of factors go into seasonal outlooks: Ocean temperature trends, location of warm and cool pools, analysis of pressure patterns over the higher latitudes and Pacific Ocean, persistence. Contrary to popular belief, outlooks are formulated differently than day-to-day forecasts. The cold winter has told us that persistence forecasting can trump other variables because it makes the most sense. The atmosphere is often times slow to respond to changes so why mess with the prevailing pattern if it's strong.  This spring has shown us that although the winter variables remain, as a collective, the result can be quite different with a lot of variation.

May has been well above normal--warmest first 11 days since 1965 in northern Ohio.

Before we talk about Summer 2015, let's head back to last summer (2014). Ocean temperatures were still dominantly warm in the north and east Pacific nearing the west coast. Tons of talk about a Super El Nino faded as the equatorial Pacific temperatures dropped into neutral territory or slightly weak/central. Below are the ocean temperature anomalies for the overlapping months starting in April and ending in September.

The ridge in the west driven by the warm coastal water continued to dominate into the summer.

The Bermuda High made a late season resurgence in the southeast which boosted temperatures by Labor Day. Cleveland's last 90 occurred on September 5th which was also the last 80 degree day until early may of this year.

Overall, the lack of any Bermuda High signature kept temperatures across the Ohio Valley and midwest below average for much of the summer

Notice how the Pacific water temperatures were somewhat reversed during the hot summers of 2010 and 2012.
 The resulting temperatures were above normal coast to coast in 2010 and 2012.

The conditions in the Pacific are much different since those hot summers of 2010 and 2012.  You can see the smaller Pacific changes since last summer...

... The warm pool along the west coast is getting warmer and more concentrated. The cool pool northwest of Hawaii is building. Equatorial ocean temperatures in the ENSO 3.4 region have risen along with some larger basin increases more than at this time in 2014.


According to the TAO PROJECT SITE, average ocean temps increased 0.4 degrees since January in equatorial Pacific down to 300 meters.  After sifting through the data, a quick volume calculation shows the increase in the volume of warmer water in the equatorial eastern Pacific since January is equivalent to the volume of Lake Erie 29 times over! That's a ton of water but it's still 5 TIMES LESS than what was present in early 1997 before the Super El Nino formed.

Big question: Will this evolve into a more significant El Nino than this past winter? CPC forecasts are calling for it.  The IRI forecast as well so I don't think there is any reason to stray from those blends. But I am skeptical of this turning into a major El Nino event. Too much warm water off the coast of Australia which keeps pressures low. Cooler water would keep high pressure west which would promote more westerly wind bursts keeping the El Nino machine churning and building.  Check out a great El Nino/La Nino video which covers the importance of the WESTERN COOL POOL from Australia's Bureau of Meteorology.

During the Super El Nino early stages in 1982 and 1997, the eastern Australian cool water was a dominant feature. The other strong El Ninos which started in 1972, 1965 and 1957 all had cool western Pacific water.

Until some western Pacific cool water develops along with continued moderate eastern/central warming this summer resulting in an MEI response, I'm staying bearish.

El Ninos circled

In my initial analog, I used last year along with several years with similar MEI and ONI indices coinciding with a building El Nino which weakens late this year in time for the following winter. 2005, 1993, 1980, 1977 and 1953 for starters.  The late 1950s are a very good match along with the late 1960s. 

April sea surface temperature blend looks like this:
The resulting summer sea surface blend looks like this.

Without taking into account the weak El Nino, the summer blend calls for below temperatures across the Ohio Valley this summer with slightly above normal precipitation.

Incorporating the El Nino yields a slightly different result for JUNE through AUGUST: