El Nino has been making headlines lately and many are wondering what it's effect might be on weather prospects for the 1998 total solar eclipse. The short answer is we just don't know. Meteorology and especially weather forecasting are not exact sciences. When you add in the variability of a poorly understood phenomenon like El Nino, it makes the job of predicting weather prospects even more difficult. Nevertheless, the following comments by several well known 'eclipse' meteorologists may shed a little light on the subject.

From: Michael L. Branick
      National Weather Service Forecast Office 
      Norman, OK 73069
Date: Thu, 7 Nov 1996

For your 'net surfing pleasure, I located the following web sites with 
very good info on the El Nino - Southern Oscillation (ENSO) phenomenon:
     
NOAA - El Nino Home Page
     
An "El Nino home page" with a decent overview of the phenomenon and 
links to several key sites, including the latest ENSO advisory from 
the Climate Analysis Center (CAC).  

Another excellent site is at
     
Understanding ENSO and Forecasting Drought
     
with a very good, concise description of El Nino and its global 
effects on rainfall.  Good news is found here under the section "ENSO 
and drought around the world," where it states in the 2nd to last 
paragraph that abnormally dry conditions have been noted in Central 
America and the Caribbean Islands during warm ENSO episodes.  I think 
one can presume that dry conditions correlate well with fewer clouds 
on average.
     
Forecasts of ENSO conditions have been notoriously unreliable beyond 
about 6 months.  They often conflict.  Present conditions are more-or- 
less neutral, and warm (El Nino) conditions currently are not expected 
to develop this coming winter. Next winter is still too far away to 
predict reliably.  The cycle varies from 2 to 7 years, so with the 
last one around late '93 and early '94, we're getting closer to being 
due for a warm episode.  The latest advisory from CAC is from April 
'96, meaning there have been no significant developments since then, 
and none are expected in the near future.
     

From: Joe Rao
      Skywayinc@aol.com
Date: Wed, 25 Jun 1997

I frankly don't think that El Nino would play a major factor in the 
eclipse weather situation for next February since most of the "action" 
will be taking place in the so-called "torrid zone" (between the Tropics 
of Capricorn and Cancer).  Farther to the north. . . if indeed some 
predictions of a significant El Nino for next winter verify. . . 
it would seem to suggest an active storm track along the southern tier 
of the U.S., to perhaps up along the U.S. Eastern Seaboard 
(that's what happened during active El Nino years in the 1980's).
Again. . . I would think that the Caribbean would be spared
of any truly "adverse" weather. . . but since I really haven't done 
a study on it. . . or seen anything written about affects of an El Nino 
on Caribbean weather, I can't be 100% sure.

Subject: ENSO and solar eclipse viewing
Author:  Chet Ropelewski
         NOAA Climate Prediction Center at W-NMC5
Date:    8/19/97 8:08 AM

This is the second time in my career that I've had a request for 
long range guidance on weather for a solar eclipse. The last time was 
30 years ago when, as a field forecaster in the Air Force, I was asked 
for flight level (20 000 ft as I recall) winds, for a C-130 that was 
going to chase an eclipse six months down the road.  The skill level 
for these single-event long-range forecasts hasn't improved any in the 
intervening decades when it was zero.  
     
The conditional probabilities for the seasonal (Oct to Mar) ENSO 
influence over the Southest US favor wetter conditions, presumably 
cloudier.  The Caribbean, on the other hand, tends to be drier, 
perhaps suggesting less cloudiness, but I know of no studies to 
support this.  If the ENSO follows the composite (average) conditions 
we can expect a stronger sub-tropical jet extending eastward from the 
Pacific through the Gulf of Mexico.
     
Updates on the progress of ENSO can be found on our home page:

NOAA Climate Prediction Center Home Page

Subject: El Nino and 1998 eclipse
Author:  Jay Anderson
         Environment Canada
Date:    29 Sep 97

Recent information I've come across suggests that the effects of el Nino 
are somewhat more pronounced than we've indicated so far. An analysis of 
rainfall for the past 20 ENSO events shows that northern South America 
has never had above normal rainfall in the months from July to March 
inclusive. Eighty percent of el Nino years had rainfall amounts which 
fell in the driest third of the climatological record - on average, 
about 30 mm less water that normal. This is a very powerful indication 
that the weather is very likely to be drier than usual for the eclipse. 

Having said this, it is only a small leap of faith to suggest that the 
weather will also be sunnier than usual. There is, after all, a fairly 
large correlation between the presence of rainfall and clouds (though 
not a perfect one...).

The area of this study encompasses the entire northern third of South 
America, so the fine scale details of the weather on the eclipse track 
are somewhat obscured. A slightly more focussed study indicates that the 
most likely weather for the upcoming el Nino event, from the Columbian 
border to the Caribbean islands is "warm and dry" from July to March. 
The signal is somewhat less distinct over northwest Columbia and the 
Panama border, where the same dry and warm conditions are suggested only 
until October 1997.

A complete discussion of these el Nino impacts for eclipse chasers can 
be found at International Research Institute for Climate Prediction.

More information can be found at NOAA Office of Global Programs.

This is too good an eclipse to let a little global topsyturvey weather 
disturb...

From: Michael L. Branick
      National Weather Service Forecast Office 
      Norman, OK 73069
Date: 30 Sep 1997

     
Everyone seems to be going El Nino crazy.  US News & World Report has 
it plastered on the cover of their current issue, and discusses what 
amounts to paranoia in California (roofers price-gouging concerned 
homeowners, sales of parkas and winter coats way up, etc etc).  I even 
have word that Colorado car dealers are advertizing El Nino will make 
it such a bad winter there that you should go out now and get a 4x4.  
We're being inundated with calls and inquiries from both a concerned 
public and a sensationalistic media that wants to blame virtually 
every current and future weather anomaly on El Nino.  Once again, we 
are dealing with a scientifically-ignorant public and finding 
ourselves having to tiptoe through the tulips to avoid fanning the 
flames that the media gladly will flame for their own benefit.
     
Yes, it's fully developing and yes, it's arguably the strongest one by 
far in recent history - at least at this point in time.  It could be 
peaking now (earlier than its usual early- to mid-winter peak), and 
could begin to weaken over the next several months.  Or it could 
continue to increase toward a wintertime peak, in which case we would 
be looking at an event of unprecedented magnitude.  In either case, we 
are dealing with something basically that we've never seen before in 
terms of its timing and magnitude, so there's virtually no way we can 
know for sure how it will affect general weather patterns.  We can 
make an educated guess based on patterns observed during previous 
strong events, but each event is different.  And since this one is SO 
different, we may see anomalies very different from prior analog 
seasons.  
     
As far as the Caribbean in late winter, all that we care about is a 
3-4 minute period on the afternoon of 26 February.  I look at 
climatological patterns as a sort of handicapper's tool, providing 
odds on the chances of success (i.e. clear skies), but you always have 
to consider the longshot as well as the favorite.  If in fact the 
Caribbean has shown a dry bias in past events, it may mean the odds 
are better than average for clear skies on a given day.  But if one 
cloud passes by the right place at the wrong time during an otherwise 
clear period, the odds wouldn't mean squat even if they did nail the 
general trend.
     
Of more concern may be Soufriere Hills, the volcano on Monserrat that 
probably will drive quite a few eclipse chasers away from the 
Guadeloupe/Monserrat area (and add to the crowd at other places like 
Aruba, Curacao, Venezuela, etc.).  It still threatens to blow big 
time, as far as I know, and whether it does or not, there will be a 
continuing risk of obscuration by the ever-present ash cloud 
throughout the immediate area of the volcano.  I'm working on 
obtaining some climatology on prevailing winds in that area, but once 
again climatology may be of limited use in this anomalous situation as 
this El Nino probably will throw prevailing winds out of kilter over a 
large part of the tropics.  Whatever the case, I have serious doubts 
that viewing in the Aruba/Curacao area would be affected at all by 
volcanic ash.  In fact, wouldn't a thin high-altitude ash layer make 
totality even more spectacular (a la the persistently-vivid sunrises 
and sunsets for a year or more after Mt. Pinatubo erupted in '91)?  
   

WebMaster: Fred Espenak Planetary Systems Branch - Code 693 e-mail: espenak@lepvax.gsfc.nasa.gov NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771 USA