January 11th, 2010

2010 Annular Solar Eclipse PFS Bulletin No. 3

Published at 0:29. Filed under Precision Forecast Service; no comment so far.

FOREWORD

This is 2010 Annular Solar Eclipse PFS Bulletin No. 3, issued in both English and Chinese. There are some changes on the forecast philosophy. The forecast diagrams mentioned below may be found at http://7timer.y234.cn/V3/product.php?language=en&product_id=2, https://www.fnmoc.navy.mil and http://www.ecmwf.int. Numeric forecast for various locations may be found at http://7timer.y234.cn/V3/product.php?language=en&product_id=1. RSS feed of this service is available at http://7timer.y234.cn/V3/wordpress/?feed=rss2&cat=46.

ANALYSIS

NCEP GFS JAN10/06Z's forecast shows a significant westerly trough over 105-107E at 25N-35N, the associated wet area reaches 116E over the annularity path. Over the east, the 1030hPa contour reaches 30N, but the near-surface wind forecast suggests the winter monsoon has weaken at that time.

ECMWF JAN10/00Z's forecast shows the same westerly trough over western China, but is about 5 degrees west of GFS's forecast. Meanwhile, ECMWF gives a slightly stronger winter monsoon persisting over East China.

FNMOC NOGAPS JAN10/06Z's forecast gives an even more westward westerly trough, centred at 95E, 25N and extend to West Sichuan Plateau. NOGAPS also expect a strong but weakening winter monsoon persisted over east, with 1030hPa contour reaches as south as 25N. NOGAPS also notes low visibility (<10km) may be applied at Sichuan Basin and Zhengzhou nearby area. FNMOC EFS JAN10/06Z's forecast suggests a chance for significant rainfall at 0-20% is expected along the annularity path over Yunnan, Sichuan and Chongqing.

For analyses of the models above, we can depict: a westerly trough lies at somewhere over the northern Indo-China Peninsula, and a winter monsoon is weakening over mainland China; however there is significant divergence over the location and strength of the westerly trough between the models.

FORECAST

Since the divergence between the models is significant, the uncertainty of this forecast increases to moderate to large. The situation varies over the models. If GFS gets it right (on an eastward trough and a weak winter monsoon), then we can expect a fair weather over the west of Yunnan, but generally poor sky around Sichuan Basin and along the annularity path over east. However, statistically ECMWF has a better performance, and what is more, NOGAPS also suggests a slow moving trough, so in this forecast the author consider the situation of a slow moving trough versus a slow weaken monsoon. It should point out that many weather websites employ GFS, which is somehow against the philosophy of this forecast, as their numeric model, so there can be significant difference between this forecast and the weather information from the internet.

Local forecasts are listed below.

• In Myanmar: partly cloudy, with some haze in valley. More clouds to the northeast.
• In Yunnan, China: mainly cloudy or overcast along the annularity path, may be a few rain patches. Rains more likely over east of 102E.
• Around Chongqing, China: foggy with drizzles.
• Around Shiyan and Nanyang, China: sunny or less cloudy weather possible with fair visibility for solar observation at low elevation.
• In Shandong, China: sunny weather possible, but the visibility may be low for solar observation at low elevation.

NEXT UPDATE

January 12 at 1600 UTC or when changes apply on forecast philosophy.