Highlights - June 2001
Near-normal conditions prevailed across the
tropical Pacific during June 2001. Sea surface temperatures (SSTs) across the tropical
Pacific were again near normal during the month (Fig. T18),
with the Niņo 3, Niņo 3.4, and Niņo 4 region indices all within 0.2°C of 0°C (Table T2). The Niņo 3.4 and Niņo 4 values were positive for
the first time since the end of the 1997/98 warm episode (Fig. T5).
The equatorial oceanic thermocline remained deeper than normal in the western Pacific,
deepened in the central Pacific, and remained shallower than normal in the extreme eastern
Pacific during the month (Fig. T15). Consistent with this
pattern, oceanic temperatures at thermocline depth were above normal throughout the
western and central Pacific and below normal in the extreme eastern Pacific (Fig. T17). Over the past few months, the region of above
normal ocean temperatures has shifted east, with positive anomalies at thermocline depth
observed across the equatorial Pacific west of 120°W (Fig. T17).
Tropical convection during June was near normal over the west-central and central
Pacific and slightly enhanced over the western Pacific and Indonesia (Fig.
T25). Over the past few months, the pattern of tropical convection over the
western and central Pacific, which has persisted since mid-1998 has weakened (Fig. T11). Elsewhere, convection was enhanced over India and
the southern part of the Sahel, implying a good start to the rainy seasons in these two
The low-level (850 hPa) winds across the Pacific basin featured near-normal easterlies
across the entire equatorial Pacific (Fig. T20). Enhanced
equatorial easterlies had persisted across the western Pacific since the onset of cold
episode conditions in mid-1998 (Fig. T7). The West Pacific
850-mb wind index value of 0.1 is the smallest value observed since March 1998 (Fig. T4). At upper levels, near normal winds were observed
over the equatorial Pacific, while easterly anomalies were observed throughout the global
subtropics of both hemispheres (Fig. T21). These easterly
anomalies were associated with enhanced subtropical ridges (Fig.
T22), which are typically observed during the mature phase of a cold episode.
The sea level pressure (SLP) pattern during June featured negative SLP anomalies
throughout much of the western and central tropical Pacific and small positive anomalies
over the extreme eastern Pacific and South America (Fig. T19).
This pattern was associated with small values of both the Southern Oscillation Index (SOI)
(-0.1) and the equatorial SOI (0.7) (Table T1, Fig. T2).