report.200108081933.climate

EPIC WEATHER/CLIMATE SYNOPSIS

Date(UTC): 2001/08/08 19:33
Author: John Bates
Submitted at(UTC): 20010808:19:45
Revised at(UTC): 20010817:20:36

CLIMATE CONDITIONS:

Near normal climate conditions prevailed across the tropical Pacific and east Pacific areas in Spring and early summer. SST anomalies were near zero and surface easterly winds were also near normal. There have, however, been more frequent episodes of westerly wind in the far western Pacific than is usual for this time of the year. These westerly winds have been associated with easterly Kelvin wave episodes in the atmosphere and also the generation of easterly Kelvin waves in the ocean. The oceanic Kelvin waves have helped push positive subsurface thermal anomalies from the western and central Pacific to the east Pacific over the past several months. The most recent oceanic equatorial Kelvin wave continues to propagate eastward along the equator and is currently located at about 120 W (this shows up nicely in the TAO data display product ^� assorted plots ^� 5day EQ UWND SST 20C anoms). This wave will effect conditions at the start of EPIC operations. The wave before this produced 1-2C SST anomalies upon reaching the coast of South America. Because subsurface anomalies are increasing, we expect at least a similar warming from the Galapagos to the coast of South America during the last two weeks of August. These, however, are transient events. Some ocean models suggest that upon hitting the west coast of South America, the equatorial Kelvin wave propagates poleward in each hemisphere as a coastally-trapped wave. A MJO is currently moving into the far western Pacific and this may generate additional westerly wind activity and may effect convection in the east Pacific ITCZ by late September

SYNOPTIC CONDITIONS:

The equatorial SST front in the east Pacific is well developed. At 95W, the front is located at about 3N and at about 1N at 85W. Instability waves are evident on the front only to the west of 100W. South of the equator, stratus is abundant east of 85W but west of 85W it transitions into open cellular cumulus. Skies are mostly clear over the cold tongue water near the equator. North of the equator, we have mixed stratus-cellular cumulus cloudiness just north of the SST front and continuing north to the ITCZ near 8N. A significant SST anomaly of +0.5-1.5 is found from about 5-15N and extending from the coast of central American west to about 110W. This may enhance convection in the EPAC ITCZ and produce convection over a wider latitudinal range than normal. This may also effect aircraft operations along 95W in that there may be more widespread convection along the 95W transects than normal.