JQP,
Whither the weather? Thought this would cheer your weekend, and all the good SD'ers, the girl child prospers!:
CLIMATE PREDICTION CENTER/NCEP
September 10, 1999
The overall patterns of oceanic surface and subsurface temperatures in the
equatorial Pacific indicate that cold episode conditions (La Niña)
strengthened during August. This is a reversal of the weakening trend that
was observed from the beginning of the year through July. During August
negative SST anomalies strengthened in the equatorial Pacific (Fig. 1,
compare left panels), and negative anomalies more than 1°C below normal
extended from 170°W eastward to 120°W. There has also been an increase
in the strength of the anomalous low-level easterly winds during the last
two months, and a continued suppression of convection over the central and
western equatorial Pacific (Fig. 1, center and right panels, respectively).
Consistent with these features, the thermocline has been deeper than
normal in the western equatorial Pacific and shallower than normal in the
eastern equatorial Pacific. This has resulted in a dipole pattern of positive/
negative subsurface temperature anomalies in the western/ eastern
equatorial Pacific (Fig. 2), which is typically observed during the mature
phase of cold episodes. The lack of any significant eastward shift in the
positive subsurface temperature anomalies in the west-central equatorial
Pacific indicates that the cold episode is likely to continue for the next
several months. This assessment is supported by the most recent NCEP
coupled model forecasts and other available coupled model and statistical
predictions indicating cold episode conditions persisting through May 2000.
Weekly updates for SST, 850-hPa wind, and OLR are available on the Climate
Prediction Center homepage at: cpc.ncep.noaa.gov (Weekly
Update).
La Niña
Discussion updated: September 22, 1999
Cold episode (La Niña) conditions strenthened throughout the tropical Pacific during August.
Sea surface temperatures (SSTs) averaged more than 1°C below normal across the tropical
Pacific between 170°W and 120°W. Also, the oceanic thermocline shoaled across the
east-central and eastern Pacific during the month with temperatures at thermocline depth
decreasing to more than 4°C below normal in that region. Tropical convection [as inferred
from anomalous outgoing longwave radiation (OLR)] remained suppressed across the western
and central equatorial Pacific and enhanced over Indonesia and the eastern Indian Ocean
during the month. The low-level equatorial winds have remained stronger than normal over the
western and central Pacific since June 1998, and weaker than normal in the eastern Pacific.
The latest forecast models are fairly consistent in predicting cold episode conditions to
continue into March-May 2000.
Climate Prediction Center
National Centers for Environmental Prediction
NOAA/National Weather Service
W/NP52, RM 605, WWB
5200 Auth Road
Camp Springs, MD 20746-4304
e-mail: wd52vk@hp31.wwb.noaa.gov
Regards to all,
Roebear |
