July 22 Great Solar Eclipse PFS Bulletin No. 13

I'm about to leave now so I write it short. Generally speaking no big changes on the models. The hope for totality area between Chengdu and Wuhan is now moderate, as on 500hPa and 700hPa there are ridges on the diagram. But after all you are highly advise to check high resolution satellite image started from now. Over Sichuan Basin there are likely to have some low and mid clouds as caused by terrain, meanwhile the hope for area over eastern Yangtze Valley remains weak, but I heard that Tongling City will fire rockets to get the clouds away. On the other hand, one of my friend rang Shanghai Meteorological Bureau and confirmed that Shanghai won't send rockets for clear.

This bulletin shall be the last one before the event, I hope everyone will have the best luck over the a few minutes.

Quanzhi @ Shangri-La

July 22 Great Solar Eclipse PFS Bulletin No. 12

EDITIONAL NOTICE

The server at NAOC (National Astronomical Observatory of China) was scheduled to be offline for maintenance on July 17 at 0400 UTC to 0800 UTC. However, the server was still offline until 1520 UTC due to some technical problems, led to the cancellation of July 17's update. Meanwhile, my departure delayed from July 18 to 19 for some reasons. Thus, bulletin No. 12 would be my final bulletin in detail for the eclipse. So I include all the information available to manage to make my best guess in this bulletin. During these days, I have experienced a work with hard pressure. I would like to have my most grateful thankness to all of you for your supports. Many people (including me) have work hard for many days for the event, and I wish best of luck on July 22 for every of them.

I have made decision to a 4,100m highland in northern Shangri-La (at the edge of Tibet Plateau) for the eclipse. I will fly to Kunming later tomorrow. Internet connections should be available until July 21, so I may be able to write a few lines when possible and necessary.

OVERVIEW

This is July 22 Great Solar Eclipse PFS Bulletin No. 12, issued in both English and Chinese. The forecast reasoning has not changed since previous bulletin. There is only 4 days away from the event. The uncertainty for this forecast remains very small. The forecast diagrams mentioned below may be found at http://7timer.y234.cn/V3/product.php?language=en&product_id=2 and http://www.fnmoc.navy.mil. Precision numeric forecast for exact 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 JUL18/00Z's run depicts the following:

1. Western Pacific subtropical high is rapidly weakening from tau 72 thru tau 96 (JUL21/00Z to JUL22/00Z), with its 500hPa 5880gpm contour drifting eastward from mainland China to around 140E. However, 500hPa streamlines forecast still depicts a weak anticyclone (a splitted high) over South China at JUL22/00Z, with a northward ridge locates at about 110E.
2. A Northeast China vortex locates around 130E 46N as indicated by 500hPa geopotential heights and streamlines forecast for JUL22/00Z, with a shallow trough developing and moving from 124E at tau 72 to 133E at tau 96. At tau 96 the trough is expected to extend to northern Ryukyu Islands.
3. A westerly flow is located along 30N as indicated by 700hPa isotachs forecast around tau 96, an associated 700hPa trough is located around 120E 34N to 126E 40N with a 850hPa shearline. An associated area of positive vorticity will move across East China until tau 108.
4. The main body of Arabian Sea subtropical high remains west of 70E around tau 96, a low pressure is located in eastern India Peninsula.

ECMWF JUL18/00Z's run depicts the following:

1. 500hPa geopotential heights of JUL22/00Z also revealed a rapidly weakening subtropical high over East Asia, the situation has no significant difference with the forecast of GFS. The situations of a low pressure over India Peninsula and the westerly flow over East Asia (revealed by 850hPa wind speed) are also close to the GFS's.
2. 850hPa shearlines at 120E 32N to 127E 34N and 105E 30N to 118E 33N are expected, with a strain of low pressures along the Yangtze River.

FNMOC NOGAPS JUL18/00Z's run depicts the following:

1. Western Pacific subtropical high is rapidly weakening from tau 48 to tau 96, with no area higher than 5880gpm over mainland China at tau 84 (JUL21/12Z; for a comparasion, GFS suggests a splitted high with intensity over 5880gpm is still visible over mainland China). At tau 96, the 5880gpm contour locates around 150E, which is also more eastward comparing with the forecasts by GFS and ECMWF. In all, NOGAPS presents a faster-weaken subtropical high compare to GFS and ECMWF. However, a ridge can be identified from the 500hPa streamlines forecast for JUL22/00Z, extending from 120E 25N to 105E 31N.
2. A Northeast China vortex locates around 128E 52N as indicated by 500hPa geopotential heights and streamlines forecast for JUL22/00Z, with an insignificant trough over northern Korea Peninsula. The intensity of this trough is apparently weaker than the expectation of GFS.
3. A westerly flow is located along 30N as indicated by 700hPa isotachs forecast around tau 96, an associated 700hPa trough is located around 110E 30N to 118E 34N with 700hPa and 850hPa shearlines. An associated area of positive vorticity will lingering around Central China around tau 96.
4. The main body of Arabian Sea subtropical high remains west of 75E around tau 96, a low pressure is located in Gulf of Bengal.

For analyses of three numeric models above, we can now depict:

1. Western Pacific subtropical high will be weakening dramatically around July 21-22, this conclusion is supported by the consistency of all three models as well as the southward behaviour of Qinghai-Xizang anticyclone ridge, the occurence of an El Niño event and the declination of Southern Oscillation Index (SOI). However, the models have also suggested that a weak ridge is possible to remain around the northern part of South China.
2. A significant shearline will be located somewhere along the Yangtze Valley at July 22, with its exact position and intensity being determined; the Southwest China vortex shall be weak.
3. India Peninsula will mostly be controlled by a low pressure instead of a strong Arabian Sea subtropical high at JUL22/00Z.

The uncertainty for this forecast remains very small as the results from all three models are consistent. We shall note that many statistic studies have showed that the ECMWF model is superior than all other models for forecast within 120 hours.

By July 18 at 09Z, Typhoon Molave (07W) is located near Hong Kong and shall be dissipated overland within days. It is unlikely that Molave will affect the weather of July 22.

HUMAN FORECAST

The forecast is remains pessimistic. According to the results of the models and past studies, there seems to be only the luck few who can get the totality. The uncertainty has further reduced since the consistency of three models remains good. Local forecasts as well as advisories of usage are listed below.

Totality area over India:

• Prognostic Reasoning: the Arabian Sea subtropical high remains moderate and is unlikely to bring fine weather for India, a low pressure around the east coast may bring unstable weather.
• Forecast: mainly cloudy over western and eastern totality area, may be mostly clear around Patna.
• Advisory: to weather of India the author is not as familiar as China's. However, due to the lack of an in-control subtropical high and an occurence of a low pressure around the east coast, a clear weather over the entire zone is unlikely. GFS indicates a generally cloudless weather around Patna, while FNMOC EFS predicts a precipitation chance of 20-90% over the totality zone during the day.

Totality area over western Sichuan, China:

• Prognostic Reasoning: the Southwest China vortex is expected to be weak, however the Arabian Sea subtropical high is also moderate, thus, extreme weather over large area is not expected.
• Forecast: mostly cloudy over west, including big Shangri-La (Deqin, Derong, Daocheng), may be suitable for eclipse for some lucky area. More clouds over eastern part (Gongga Shan/Minya Konka, Ya'an, Emei Shan) with moderate precipitation chance at the morning according to FNMOC EFS.
• Advisory: weather forecast for highland is always very challenging, the author has investigated a number of weather archives for Derong and Minya Konka, the relationship between basic meteorological elements and actual weather appeared to be very complex. remarks from experienced local people or guides shall be employed seriously if any. Long term statistic data showed that northern Shangri-La area has a good possibility of being clear even in July. It is reported that the total sunshine time for Derong is 2,700-3,000 hours. For eastern area, July is the rainy season, and the forecast we have does not support a significant chance for an exception.

Totality area over Chengdu-Chongqing Plain, China

• Prognositic Reasoning: the lack of a significant Southwest China vortex suggests the weather shall not be too bad. However, as this area is at the buttom of a trough, plus a weak anti-clockwise stream in-controlled, the weather will not be too opmistic. The weather can be slightly better over east as all three models suggest something like a weak ridge or a weak high.
• Forecast: mainly cloudy with a few showers. There is a weak chance that the weather to be better over east.
• Advisory: there appears to be no significant system in-controlled. It can say with some confidence that rains or clear over large area is unlikely; however, a chance of less clouds and a few more sunshines can not be ruled out, as three models had indicated. The author should point out that minor systems like the weak ridge mentioned above is difficult to predict, so please follow the most recent weather information before you make decision.

Totality area over Hubei Province, China

• Prognositic Reasoning: all three models proposed something like a weak ridge or a weak high over west, but the most area is expected to suffer from affection of a shearline locates over the north.
• Forecast: weak chance for western area (like Enshi) to be better; mainly overcast over the entire province, but clouds may be slightly thinner (may permits a partial eclipse observation) over the south since it locates further from the shearline. Light rain is possible for some area throughout the day.
• Advisory: it can be say with some confidence that decent weather for most area is unlikely. Base on experience, a region of cloudless will locate somewhere around the shearline, however, its size is depending on the intensity of the shearline, which is hard to predict. In all, get prepared to move around and follow the most recent weather information. If possible, check the high resolution satellite image on the early morning of July 22 and make final decision.

Totality area over South Anhui Province, China

• Prognostic Reasoning: the low level shearline is expected to locate over the northern part of Anhui Province, whether or not that its associated clouds would affect sites among South Anhui depends primary on the intensity and exact location of the shearline, which the three models have not yet agree with each other.
• Forecast: since we have noted that ECMWF is more reliable than other two models, we may take ECMWF as consideration. The weather will be generally overcast with rain patches according to the forecast of ECMWF, but may be slightly cloudless over south -- like Huangshan. If NOGAPS or GFS gets it right, it will be cloudy, with much higher chances for the appearance of cloudless regions.
• Advisory: as noted above, the intensity and exact location of the low level shearline play an important role on judging the possibility for South Anhui to get a decent view. However, the southern area of South Anhui might be slightly more promising since it will keep a distance from the shearline no matter which model gets it right. In all, check the high resolution satellite image on the early morning of July 22 to make final decision if you can.

Totality area over pan-Yangtze River Delta, China

• Prognostic Reasoning: the low level shearline is expected to locate around Shanghai. Since the shearline here is close to the front lingering from East China Sea across Japan, the possibility for this shearline to be a weak one is not high.
• Forecast: generally overcast with rain.
• Advisory: weather over this area is less promising than those above. However, weather is varying from day to day, any kinds of situation cannot be ruled out.

Totality area over Ryukyu Islands, Japan

• Prognositic Reasoning: a westerly flow is lifting over this area, however the trough is well clear to the north.
• Forecast: mainly cloudy, with a few or some sunshines.
• Advisory: weather over ocean is quite dynamic. Although this area is not expected to be controlled by subtropical high as usual, cloudless regions are probable.

Conclusion and Remark

• Generally speaking, there is no place to be better from cloud than any other places, except for places around Shanghai seems to be less opmistic according to the forecast we have.
• Weak ridges noted above may bring slightly better weather, however they are hard to be precisely predicted.
• You may better stay at the site you picked and accept whatever happened to you. If you can fly off or can drive around, keep monitoring the weather, preferably weather diagrams prior to July 21 and satellite images in the final hours, and make final decision accordingly. A fine collections of the resources by meteorolgist J. Anderson is available at http://home.cc.umanitoba.ca/%7Ejander/tot2009/fcsts.htm.

12KM MM5/GFS FORECAST

The 12km MM5/GFS model is online and is now under test. Eclipse map produced by Occult 4 has been combined with the cloud cover graph. Please download the KML file and open it with Google Earth (http://earth.google.com/). The forecast time is July 22 from 0000 UTC to 0400 UTC with 1-hour interval, the forecast region includes most of totality area over China. This model shall be updated automatically everyday at about 0200 UTC.

Warning: by using this product you have acknowledge that the product is under very first test and is only posted as an alpha version, 7Timer! is not responsible for any damages or expenses you may incur as a result of any inaccuracy. To help you better assess the products we have, you are highly advised to read the tips below before using.

• Tip 1: 7Timer! has two models now, the original GFS model of 35km and 3-hour interval, which the forecast may be found at APanel section (local forecast for 72 hours) and Weachart section (charts of global for 384 hours) which you can find at the 7Timer! website (http://7timer.y234.cn/V3/product.php?language=en); and the MM5/GFS dynamic numeric model of 12km and 1-hour interval, which uses GFS data for initialization and is under very first test and is only posted here for the eclipse. My experience is that GFS is usually more reliable, despite its resolution is far from as good as MM5/GFS. So, check GFS chart when using MM5/GFS, and assess the reliability of the situation accordingly.
• Tip 2: When there are less than 72 hours from the event, APanel can be used to assess the weather condition for an exact location. However, since APanel also uses the low resolution 35km/3h GFS data, the trick given in Tip 1 still plays -- when the forecast by MM5/GFS (the product you are using) is similar to what GFS given, you may use MM5/GFS for a more precise estimate of the weather as it has a much better resolution. Otherwise, please do not take the result MM5/GFS gives too seriously.

12km MM5/GFS Forecast KML File

NEXT UPDATE

When possible. Might be July 20 at 1600 UTC or earlier.

ACKNOWLEDGEMENT

I would like to thank Dr. Cui Chenzhou from National Astronomical Observatory of China for working with the server problem overnight. I would also like to thank Zhang Linna from Beijing Meteorolical Bureau and President Dickson Fu from Sky Observers' Association (Hong Kong) for their valuable discussion and help. I would also like to thank Cheng-Su Diandian for her support of this work.

July 22 Great Solar Eclipse PFS Bulletin No. 11

EDITIONAL NOTICE

This bulletin is revised at July 16 1730 UTC, missed tropical cyclone information is added, and the precision forecast map comes online.

OVERVIEW

This is July 22 Great Solar Eclipse PFS Bulletin No. 11, issued in both English and Chinese. The forecast reasoning has slightly changed since previous bulletin. There is only 6 days away from the event. The uncertainty for this forecast is upgraded to very small. The forecast diagrams mentioned below may be found at http://7timer.y234.cn/V3/product.php?language=en&product_id=2 and http://www.fnmoc.navy.mil. Precision 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 JUL16/00Z's forecast on 500hPa geopotential heights of JUL22/00Z revealed a weak subtropical high over western Pacific with an oblique ridge. An animation with nearby taus shows the subtropical high is weakening, with 5880gpm contour stays east of 140E at JUL22/00Z, but a weak splitted  high can still be spotted by 500hPa streamlines of JUL22/00Z although no contour is shown on the geopotential heights. On the other hand, a westerly trough is locating over Central China, and a 850hPa shearline is lifting over the Yellow Sea and Jiangsu Province (around 120E 34N). The position and the intensity of the Arabian Sea subtropical high did not suffer a major change since last run. Meanwhile, forecast for 300hPa geopotential heights revealed that the ridge of Qinghai-Xizang anticyclone locates south of 30N.

ECMWF JUL16/00Z's forecast on 500hPa geopotential heights of JUL22/00Z has retracted the claim of a strong western Pacific subtropical high to be persisted around July 22. Its situation is similar to NCEP GFS's now although the intensity of the subtropical high is still higher than the later's, with the 5880gpm contour reach west of 140E and a splitted subtropical high locates over Taiwan (as noted above, this splitted high does also appeared on GFS's forecast for JUL21/12Z for an intensity of over 5880gpm but not for JUL22/00Z). Weak 850hPa shearline is still suggested over southern Jiangsu Province with no 500hPa westerly trough visible, while the monsoon over India persisted.

FNMOC NOGAPS JUL16/00Z's forecast on 500hPa geopotential heights of JUL22/00Z also depicts a weak western Pacific subtropical high, the intensity is weaker than GFS or ECMWF suggest, with 5880gpm contour east of 150E. 500hPa streamlines analyses show a weak ridge over Ryukyu Islands extending to Central China. On the other hand, an area of 850hPa positive relative vorticity can be spotted over Jiangsu Province, an associated shearline is visible on 850hPa and 700hPa streamlines analyses. The main body of Arabian Sea subtropical high locates in Saudi Arabia, with a weaker intensity comparing with GFS's forecast. Monsoon over southern India is persisted. Forecast for 300hPa geopotential heights revealed a ridge of Qinghai-Xizang anticyclone locates south of 30N, which is consistent with GFS's.

For analyses of three well-known numeric models above, we can now depict:

1. Western Pacific subtropical high is likely to be weaker than long term mean (for a long term mean graph, please refer to bulletin No. 6), all three models have depicted a highly similar result on this conclusion. A southward Qinghai-Xizang anticyclone ridge and a development of El Niño event also suggest a similar trend. However, the models have also suggested a splitted high or a weak ridge is possible to turn up around East China Sea.
2. A low level shearline can be located around 115E 33N (i.e. in Jiangsu Province), this is also suggested by all three models. The intensity of this shearline remains in question but shall not be strong. There is also a chance for a drifted southwest vortex located over Central China (suggested by GFS).
3. India Peninsula is unlikely to be controlled by the Arabian Sea subtropical high, but a monsoon will run in at that time.

The uncertainty for this forecast is upgraded to very small as the results from all three models are consistent.

By July 16 at 18Z, tropical storm Molave (07W) locates over east of Luzon and is expected to move into South China Sea in the coming days. It is likely that Molave will affect the weather of July 22.

FORECAST

The forecast is much more pessimistic than the previous bulletin since ECMWF and NOGAPS have both retract their expectation of normal-to-strong western Pacific subtropical high. The uncertainty has reduced since there is no significant divergence between the models. Local forecasts are listed below. Please be aware that these forecasts may change as there is still 6 days to go for the event.

• In India: mainly cloudy over most totality area but may have more sunshine over east (suggested by GFS). Showers are likely during the day. 
• In Sichuan and Chongqing, China: cloudy to overcast, may have a few sunshines. FNMOC EFS suggests a precipitation probability of >90% on the mountainous area west of Chengdu, but for Chengdu-Chongqing plain the probability is less than 10%. However, GFS proposes a possibility of heavy rain at Sichuan Basin produced by the developed southwest vortex.
• Around Wuhan, China: cloudy to overcast with precipitation probability of >40% according to EFS.
• Around Tongling, China: cloudy to overcast with precipitation probability of >50% according to EFS.
• Pan-Yangtze River Delta, China: cloudy to overcast. 
• Ryukyu Islands, Japan: cloudy as the subtropical high is weak.

The 12km MM5/GFS model is coming online and it is now under test, initialization for this run is at JUL14/18Z. Eclipse map produced by Occult 4 has been combined with the cloud cover graph. Please download the KML file and open it with Google Earth (http://earth.google.com/). The forecast time is July 22 from 0100 UTC to 0400 UTC with 1-hour interval, the forecast region includes most of totality area over China. Warning: by reading this message you have acknowledged that this is a service that still under test! My experience is that sometimes it is not better than the original GFS, although resolution of the later is much lower than this service. For GFS forecast maps, please refer to http://7timer.y234.cn/V3/product.php?language=en&product_id=2.

Download the KML file

NEXT UPDATE

July 17 at 1500 UTC or earlier.

July 22 Great Solar Eclipse PFS Bulletin No. 10

OVERVIEW

This is July 22 Great Solar Eclipse PFS Bulletin No. 10, issued in both English and Chinese. The forecast reasoning has slightly changed since previous bulletin. Although there is only 7 days away from the event, the divergent results given by difference models make the uncertainty for this forecast remains moderate. The GFS forecast diagrams mentioned below may be found at http://7timer.y234.cn/V3/product.php?language=en&product_id=2. Precision numeric forecast for various locations may be found at http://7timer.y234.cn/V3/product.php?language=en&product_id=1.

ANALYSIS

GFS JUL14/18Z's forecast on 500hPa geopotential height of JUL22/00Z revealed a weak subtropical high in western Pacific. On the other hand, there is an northeast vortex over Northeast China, with a 850hPa shearline over northern Bohai Sea, but there is no significant westerly trough over North China. The position and the intensity of the Arabian Sea subtropical high did not suffer a major change since last run. In all, the positions of the major systems had not been revised significantly but instead of their intensities. Meanwhile, the ridge of Qinghai-Xizang high is near 30N as spotted from 100hPa geopotential height diagram, which is nearly the same as that of last run.

ECMWF JUL14/12Z's forecast on 500hPa geopotential height of JUL22/00Z still suggested a strong western Pacific subtropical high with its 5880gpm contour reach 110E. A weak 850hPa shearline is purposed around Bohai Sea with no 500hPa westerly trough visible, while the monsoon over India persisted.

FNMOC NOGAPS JUL14/12Z's forecast on 500hPa streamlines suggested a situation similar to ECMWF's, with a splitted subtropical high centred around Wuhan. Again, no significant westerly trough can be seen around North China; but FNMOC EFS JUL14/12Z's forecast on 5640gpm contour probability of JUL21/12Z suggested a deeper-than-usual East Asia Major Trough with 90% probability that the 5640gpm to be located near 45N, and this is consistent with what GFS suggested.

By July 15 at 00Z, good disturbance 91W is activing over west of Palau while poor disturbance 94W is centred over northern South China Sea, but the probability for them to affect the weather of July 22 is low. However, we shall note that NOGAPS did suggest two weak tropical cyclones activing over western Pacific Ocean around July 22.

FORECAST

The divergent results available make it difficult to figure a confident prediction. It is encouraging to see both ECMWF and NOGAPS have suggest something promising. Local forecasts are listed below. Please be aware that they are rough due to the moderate uncertainty of enviromental forecast and may suffer major changes.

• In India: cloudy and rainy over most totality area as a monsoon run in. May be have some sunshine over Patna and further east. 
• In Sichuan and Chongqing, China: overcast and rainy as a southwest vortex is centred over Sichuan Basin according to GFS; but can be partly clear if ECMWF and NOGAPS get it right. 
• Around Wuhan, China: shall be cloudy with showers according to GFS, but can be mostly clear according to ECMWF and NOGAPS.
• Pan-Yangtze River Delta, China: situation close to Wuhan. 
• Ryukyu Islands, Japan: shall be cloudy with a few heavy showers according to GFS, but can be mostly to partly clear according to ECMWF and NOGAPS.

NEXT UPDATE

July 16 at 1500 UTC or earlier. Precision forecast for mainland China with a resolution up to 12km might be available for test by that time.

ACKNOWLEDGEMENT

I would like to thank President Dickson Fu from Sky Observers' Association (Hong Kong) for his valuable contribution to this work.

July 22 Great Solar Eclipse PFS Bulletin No. 9

OVERVIEW

This is July 22 Great Solar Eclipse PFS Bulletin No. 9, issued in both English and Chinese. The forecast reasoning has slightly changed since previous bulletin. Please note that the local forecast given here will be rough as there is still 8 days away. Uncertainty for this forecast is downgrade to fair.

ANALYSIS

GFS JUL14/00Z's forecast on July 22 at 00 UTC's 500hPa geopotential height  (Fig. 1) revealed a subtropical high in western Pacific area with an oblique (NE-SW) ridge. The shape of this subtropical high is nearly the same comparing with that of last run, with its intensity further pull up. On the other hand, the intensity of the westerly trough over Bohai Sea is further reduced than the last bulletin. The position and the intensity of the Arabian Sea subtropical high did not suffer a major change since last run, but a weak low appears over India Peninsula. In all, the positions of the major systems had not been revised significantly but instead of their intensities. Meanwhile, the shape and intensity of Qinghai-Xizang high is near the long term mean and is nearly the same as that of last run.

Figure 1: GFS JUL14/00Z's forecast on 500hPa geopotential height of July 22's 00h UTC

ECMWF JUL14/00Z's forecast on July 22 at 00 UTC's 500hPa geopotential height is significantly revised since last bulletin. A strong subtropical high over western Pacific area can be seen, with 5880gpm contour extends to around 110E, and the ridge is only slightly oblique. There is only a very weak westerly trough over Northeast China. Generally speaking, the solution for East Asia offer by both GFS and ECMWF is again different with each other, hence, the uncertainty for this forecast is downgrade to fair.

By July 14 at 09Z, good disturbance 91W is activing over west of Palau, Tropical Cyclone Formation Alert has been issued, but the probability for 91W to affect the weather of July 22 is low. 

FORECAST

The dramatically revision of ECMWF's forecast makes it difficult to figure a solid prediction. However, as GFS also raise its expectation of the intensity of western Pacific subtropical high, it can be suggested that we might get something more promising. Local forecasts are listed below. Please be aware that they are rough and may suffer major changes since the event is still 8 days away.

• In India: cloudy and rainy over most totality area as a monsoon run in, suggested by both GFS and ECMWF forecast. May be have some sunshine over Patna and further east. 
• In Sichuan and Chongqing, China: can be partly clear over high lands, a weak southwest cyclone may bring heavy clouds to Sichuan Basin. 
• Around Wuhan, China: shall be mostly cloudy with a few sunshine according to GFS, but can be mostly clear according to ECMWF.
• Pan-Yangtze River Delta, China: partly clear according to GFS, but GFS also suggests there will be cumulus that may block the sun. But shall be mostly clear according to ECMWF.
• Ryukyu Islands, Japan: shall be mostly cloudy according to GFS but mostly clear suggested by ECMWF. 

A total cloud cover graph of July 22's 00Z is shown as Fig. 2. You are warned that any precision forecasts for over a period of 3-5 days are unreliable.

Figure 2: GFS's total cloud cover prediction on July 22's 00Z, with the central line manually marked.

NEXT UPDATE

July 15 at 0300 UTC or earlier since I will be on the train tomorrow afternoon. Precision forecast for mainland China with a resolution up to 12km might be available for test by that time. I would like to thank Johnson Lau for pointing an error in this bulletin.

July 22 Great Solar Eclipse PFS Bulletin No. 8

OVERVIEW

This is July 22 Great Solar Eclipse PFS Bulletin No. 8, issued in both English and Chinese. The forecast reasoning has slightly changed since previous bulletin. Please note that the local forecast given here will be very rough as there is still 9 days away. Uncertainty for this forecast remains small.

ANALYSIS

GFS JUL13/00Z's forecast on July 22 at 00 UTC's 500hPa geopotential height  (Fig. 1) revealed a subtropical high in western Pacific area with an oblique (NE-SW) ridge. The intensity and shape of this subtropical high has been revised since last run. On the other hand, the intensity of the westerly trough is significantly reduced, with no 850hPa shear line observable, but still located near the Bohai Sea. The position and the intensity of the Arabian Sea subtropical high did not suffer a major change since last run. In all, the positions of the major systems had not been revised significantly but instead of their intensities. Meanwhile, the shape and intensity of Qinghai-Xizang high had also been revised and is now stronger and more northward than that of last run.

Figure 1: GFS JUL13/00Z's forecast on 500hPa geopotential height of July 22's 00h UTC

ECMWF JUL13/00Z's forecast on July 22 at 00 UTC's 500hPa geopotential height revealed a subtropical high over western Pacific area with an oblique ridge, its intensity has been slightly revised and is now near long term mean. A westerly trough is lifting over Bohai Sea. Generally speaking, the solution for East Asia offer by both GFS and ECMWF meets better than that of the previous bulletin.

By July 13 at 09Z, tropical depression 06W locates to the east of Taiwan and is expected to dissipate overland in a few days. Meanwhile, tropical disturbance 93W is activing near Yap, and there is a chance that it can affect the weather of July 22. ECMWF has proposed two weak tropical cyclones activing over western Pacific around July 22.

FORECAST

Examing the most recent analyses, we could find these similarities:

1. The western Pacific subtropical high is unlikely to be strong, and the appearance of an oblique ridge is quite certain (for an explication for the effect of an oblique ridge of western Pacific subtropical high, please refer to bulletin No. 4). Considering an El Niño event is now appeared to be developing, this conclusion is consistent with the correlation found by statistical studies (Zhao, 1996).
2. For mid latitute trough, it appears to locate slightly east of the long term mean, and forecast of its intensity varies from time to time.
3. Totality zone area over western India is not likely to be controlled by the ridge of Arabian Sea subtropical high.

Weather forecast over totality zone appears to be more promising than previous bulletin, since both the models had reduced their expectation of the intensity of westerly trough, plus a weak ridge may extent into mainland China. Local forecasts are listed below. Please be aware that they are very rough and may not be accurate since the event is still 9 days away.

• In India: could be mainly cloudy along the totality area since no obvious ridge and several weak lows moving around, but GFS suggest the area near Patna may be partly clear. Still uncertain.
• In Sichuan and Chongqing, China: mainly cloudy since no significant southwest cyclone is presented in this forecast. Can be partly clear at times over east and on some highlands. 
• Around Wuhan, China: shall be mostly cloudy as there is a shallow trough associated the low pressure near Bohai Sea near surface.
• Pan-Yangtze River Delta, China: mostly cloudy, slightly better than Wuhan as it would be placed further from the shallow trough. GFS has also suggest a similar situation.
• Ryukyu Islands, Japan: controlled by a weak ridge and shall be partly cloudy.

A total cloud cover graph and a high cloud cover (for clouds over a height of  6,000m) of July 22's 00Z is shown as Fig. 2 and Fig. 3, respectively. You are warned that any precision forecasts for over a period of 3-5 days are unreliable.

Figure 2: GFS's total cloud cover prediction on July 22's 00Z, with the central line manually marked.

Figure 3: GFS's high cloud cover prediction on July 22's 00Z.

NEXT UPDATE

July 14 at 1000 UTC or earlier. I would like to thank President Dickson Fu from Sky Observers' Association (Hong Kong) for contribution of the correlation between El Niño and subtropical high.

July 22 Great Solar Eclipse PFS Bulletin No. 7

OVERVIEW

This is July 22 Great Solar Eclipse PFS Bulletin No. 7, issued in both English and Chinese. The event has entered the forecast range of some numeric models such as ECMWF. The forecast reasoning has not changed since previous bulletin. Please note that the local forecast given here will be very rough as there is still 10 days away. Uncertainty for this forecast is upgrade to small.

ANALYSIS

GFS JUL12/00Z's forecast on July 22 at 00 UTC's 500hPa geopotential height  (Fig. 1) revealed a subtropical high in western Pacific area with an oblique (NE-SW) ridge. The intensity of this subtropical high is near the long term mean. Trough of low pressure associated with the northeast low is lifting across Jiangsu Province into Bohai Sea. On the other hand, a subtropical high can be seen around the Arabian Sea area. This situation is similar to the previous run, with the position and intensity of the major systems slightly revised.

Figure 1: GFS JUL12/00Z's forecast on East Asia 500hPa geopotential height of July 22's 00h UTC

Further to the 500hPa geopotential height chart, the 100hPa geopotential height forecast is shown as Fig. 2, indicating a Qinghai-Xizang high (a.k.a. the 100hPa anticyclone over South Asia) with a NW-SE ridge over mainland China comparing with the long term mean (Fig. 3, trough in solid while ridge in dot). The major westerly trough is around 120E, which is also different from long term mean. 

Figure 2: GFS JUL12/00Z's forecast on 100hPa geopotential height of July 22's 00h UTC

Figure 3: Long term mean of 100hPa geopotential height, generated by NCEP-NCAR Reanalysis products

According to the taxonomic method presented by Luo et al. (1982), the features of the anticyclone (NE-SW ridge over mainland China and a deep westerly trough near 120E) matchs the a "western style" one. Statistically, a western Qinghai-Xizang high would come with rainy weather over Yangtze Valley, eastern Sichuan, and Northern China.

ECMWF JUL12/00Z's forecast on July 22 at 00 UTC's 500hPa geopotential height revealed a weak subtropical high over western Pacific area, but an oblique ridge can be observed. Although ECMWF's forecast gives a somewhat different solution over southern Asia comparing with GFS's, a feature in common is a shear line over Eastern China on 850hPa wind chart.

By July 12 at 09Z, tropical depression Soudelor is activing over Beibu Wan and is expected to dissipate very soon. Meanwhile, the Joint Typhoon Warning Center has issued a Tropical Cyclone Formation Alert for tropical disturbance 92W. However, the chance for 92W to affect the weather of July 22 is low.

FORECAST

Examing all analyses we have, although one may varies largely from another, we found these similarities: 1) for western Pacific subtropical high, although the intensity varies from time to time, an unusual "oblique" feature is in common (for an explication for the effect of an oblique ridge of western Pacific subtropical high, please refer to bulletin No. 4). 2) for mid latitute trough, it appears to locate east of the long term mean. 3) totality zone area over western India is not likely to be controlled by the ridge of Arabian Sea subtropical high.

Weather over totality zone is generally less promising than previous bulletin, since the westerly trough over Eastern China appeared to be stronger than we had expected and the two models available (GFS and ECMWF) suggest something in common, if not exactly the same. Local forecasts are listed below. Please be aware that they are very rough and may not be accurate since the event is still 10 days away.

• In India: could be mainly cloudy along the totality area since no obvious ridge and several weak lows moving around, but GFS suggest the area near Patna may be partly clear. Still highly uncertain.
• In Sichuan and Chongqing, China: will be controlled by a southwest cyclone and shall be rainy.
• Around Wuhan, China: at the buttom of a westerly trough and shall be cloudy with a few rain.
• Pan-Yangtze River Delta, China: near a 850hPa shear line and could be cloudy with a few rain. However there shall be slightly less cloudy over the south part, GFS has also suggest a similar situation.
• Ryukyu Islands, Japan: near a deep 500hPa minor trough and shall be mostly cloudy.

A MSL pressure graph and a cloud cover graph of July 22's 00Z is shown as Fig. 4 and Fig. 5, respectively. You are warned that any precision forecasts for over a period of 3-5 days are unreliable.

Figure 4: GFS JUL12/00Z's forecast on MSL pressure of July 22's 00h UTC

Figure 5: GFS's total cloud cover prediction on July 22's 00Z, with the central line manually marked.

NEXT UPDATE

July 13 at 1000 UTC or earlier. Sorry for take it quite a while to process and analyse all the materials today. I would like to thank Zhang Linna from Beijing Meteorological Bureau and Zhou Linjiong for fruitful discussions. Thankness also goes to Shi Liaoshan and Chen Sisi for their valuable helps.

July 22 Great Solar Eclipse PFS Bulletin No. 6

OVERVIEW

This is July 22 Great Solar Eclipse PFS Bulletin No. 6, issued in both English and Chinese. The forecast reasoning has not changed since previous bulletin. No local forecast will be issued since the event is still 11 days away. Uncertainty for this forecast remains fair.

ANALYSIS

GFS JUL11/00Z's forecast on East Asia 500hPa geopotential height of July 22's 00h UTC (Fig. 1) revealed a subtropical high in western Pacific area with an oblique (NE-SW) ridge. The intensity of this subtropical high is near the long term mean. A trough of low pressure is lifting around Bohai Sea, a southwest low pressure is also lifting over the east of Tibet. On the other hand, a subtropical high can be seen around the Arabian Sea area. This situation is similar to the previous run, with the position and intensity of the major systems slightly revised.

Figure 1: GFS JUL10/00Z's forecast on East Asia 500hPa geopotential height of July 22's 00h UTC

ECMWF's JUL11/00Z's forecast on 500hPa geopotential height of July 21's 00 UTC shows a western Pacific subtropical high with a much reduced intensity and a unusual shape comparing with GFS's. A trough of low pressure is visible over the east of Yellow Sea.

By July 11 at 06Z, tropical storm 05W is activing in northern South China Sea and is expect to dissipate within days. Fair disturbance 91W and poor disturbance 92W are activing over western Pacific and may affect the weather of July 22.

FORECAST

Examing all analyses we have, although one may varies largely from another, we found these similarities: 1) for western Pacific subtropical high, although the intensity varies from time to time, an unusual "oblique" feature is in common (for an explication for the effect of an oblique ridge of western Pacific subtropical high, please refer to bulletin No. 4). 2) for mid latitute trough, it appears to locate east of the long term mean (Fig. 2). 3) totality zone area over western India is not likely to be controlled by the ridge of Arabian Sea subtropical high.

Figure 2: Long term mean of 500hPa geopotential height, generated by NCEP-NCAR Reanalysis products

Since the similarities with the result of last run, the forecast is similar to the previous bulletin. The difference is that the cloud cover is slightly increased since the intensity of the western Pacific subtropical high has reduced. The weather is expected to be partly to mostly cloudy among the Yangtze Valley, the weather around Wuhan may be slightly better than further eastern cities since it lies between the two trough. The totality area over west of Chongqing will be controlled by a mild southwest low and is likely to be cloudy with a few rain. A MSL-reduced pressure chart is shown as Fig. 3.

Figure 3: GFS JUL11/00Z's forecast on East Asia MSL-reduced pressure of July 22's 00h UTC

The totality area over western India is likely to be controlled by a saddle field and may has a mostly cloudy weather. Northern part of Ryukyu Island may be affected by a front over Japan and maybe cloudy. The weather over Pacific shall generally be fine since a subtropical high is in-control.

A total cloud cover chart made by GFS for July 22's 00Z is shown as Fig. 4, with the central line manually marked. The resolution is 2.5 x 2.5 (deg). Please note that cloud cover forecasts for over 3-5 days are generally highly unreliable.

Figure 4: GFS's total cloud cover prediction on July 22's 00Z, with the central line manually marked.

We shall note that the similarities between this and the previous forecast is quite interesting. However, since there are still some differences between GFS and other models, plus the chance for a tropical cyclone to run in, we regret to downgrade the uncertainty.

NEXT UPDATE

July 12 at 1000 UTC or earlier.

July 22 Great Solar Eclipse PFS Bulletin No. 5

OVERVIEW

This is July 22 Great Solar Eclipse PFS Bulletin No. 5, issued in both English and Chinese. The forecast philosophy has not changed significantly since last bulletin. No local forecast will be given since the event is still 12 days away. Uncertainty for this forecast is fair.

ANALYSIS

GFS JUL10/00Z's forecast on East Asia 500hPa geopotential height of July 22's 00h UTC (Fig. 1) revealed a subtropical high in western Pacific area with an oblique ridge. The intensity of this subtropical high is near the long term mean. We shall note that the oblique (NE-SW) feature of the ridge has appeared in all analyses so far we have. A trough of low pressure is lifting around Bohai Sea, a southwest low pressure is also lifting in Sichuan. On the other hand, a subtropical high can be seen around the Arabian Sea area, with the east point of 5880gpm contour locating near eastern Pakistan.

Figure 1: GFS JUL10/00Z's forecast on East Asia 500hPa geopotential height of July 22's 00h UTC

 ECMWF's JUL10/00Z's forecast on 500hPa geopotential height of July 20's 00 UTC shows a similar western Pacific subtropical high as GFS's but its intensity is reduced, with a trough of low pressure presented around the Yellow Sea. The pressure over the Arabian Sea is low. GDAPS's JUL10/00Z's forecast on 500hPa geopotential height of July 20's 00 UTC is similar to ECMWF's, with the intensity of western Pacific subtropical high further reduced.

By July 9 at 06Z, tropical depression 05W is activing near Luzon Strait and is expect to dissipate in a week. Fair disturbance 90W is activing near Chuuk Island and may affect the weather of July 22. ECMWF's JUL10/00Z run has proposed a weak tropical cyclone to the east of Hainan Dao.

FORECAST

For an explication for the effect of an oblique ridge of western Pacific subtropical high, please refer to bulletin No. 4.

The weak ridge and trough suggested by all three available models are not likely to bring very clear or cloudy weather to most totality area. The weather is expected to be partly cloudy among Yangtze Valley, except the area west of Chongqing will be controlled by the southwest low and is likely to be cloudy and rainy.

The models differ on the situation of western India, as GFS suggests a subtropical high of Arabian Sea will be in-control while ECMWF suggests a low. The weather may be acceptable for eclipse observing for some coast areas if GFS gets it right. The weather over Pacific shall generally be fine since a subtropical high is in-control.

A total cloud cover chart made by GFS for July 22's 00Z is shown as Fig. 2, with the central line manually marked. The resolution is 2.5 x 2.5 (deg).

Figure 2: GFS's total cloud cover prediction on July 22's 00Z, with the central line manually marked.

NEXT UPDATE

July 11 at 1000 UTC or earlier.

July 22 Great Solar Eclipse PFS Bulletin No. 4

OVERVIEW

This is July 22 Great Solar Eclipse PFS Bulletin No. 4, issued in both English and Chinese. The forecast philosophy has not changed significantly since last bulletin. No local forecast will be given since the event is still 13 days away from now and the forecast uncertainty is large.

ANALYSIS

GFS JUL09/00Z's forecast on East Asia 500hPa geopotential height of July 22's 00h UTC (Fig. 1) revealed a normal subtropical high in western Pacific area. The intensity of the subtropical high is further reduced compare with previous run, but the ridge is still oblique (NE-SW). This feature has appeared in all analysis so far we have. Similar to the JUL08/00Z run, a trough of low pressure appeared again in northern part of Eastern China, with a much stronger intensity than the previous run. Across the most part of central China there is a weak ridge.

Figure 1: GFS JUL09/00Z's forecast on East Asia 500hPa geopotential height of July 22's 00h UTC

Since today we will consider the forecast from ECMWF. The ECMWF's 500hPa geopotential height forecast (chart will not redistribute according to usage term) on July 19's 00Z shows a similar oblique ridge. However, a tropical cyclone is located in the northern part of South China Sea, forcing the ridge over the mainland China moving north. The deep trough of low pressure is also presented in the Yellow Sea.

By July 9 at 1200Z, fair disturbance 90W is active over western Pacific Ocean and may influence the weather of July 22. Meanwhile, good disturbance 99W is located in the east of Luzon and is expected to dissipate before July 22.

FORECAST

Before give forecast based on today's analysis, we shall first explict the situation of an oblique ridge, since this feature has appeared in all analysis and is possible to due around July 22. Generally, the ridge of western Pacific subtropical high lies horizontally near 26N in July, pushing the Meiyu front north of Yangtze Valley. The Meiyu front is not exactly horizontally since the 500hPa trough of low pressure is generally lying NE-SW (sometimes N-S), but under the effect of a horizontal ridge of the south, the front is usually lying ENE-SSW. However, when the ridge is also oblique, the slope of the front will become larger, making the Yangtze Valley not exactly entirely placing in the front. Thus, if the ridge is oblique in July 22, there will certainly causing some (most) places in the totality zone to be covered by clouds. This situation can be broke by a strong tropical cyclone in the south, such as ECMWF suggests. The downward current of air outside the tropical cyclone can keep those areas away from cloud.

According to the forecast of GFS, we can expect large areas over Eastern China -- generally east of 115E 30N (i.e. east of the trough) -- are being covered by heavy cloud. Rains are likely, since a clear shear line is presented on the 850hPa wind chart. On the other hand, the weak ridge over central China are possible to bring an acceptable weather to the totality area between Chongqing and Wuhan. However, if a tropical cyclone can turn up in the South China Sea as ECMWF suggests (we shall note that tropical cyclones are highly unpredictable over a week or so), this situation can be changed as noted above.

The totality area over India are possible to be under clouds produced by a 500hPa low pressure over northern Gulf of Bengal. Areas over east of Ryukyu Islands are possible to share a cloudless weather granted by the western Pacific subtropical high.

We shall note that there are still 13 days from the event, the uncertainty remains high.

NEXT UPDATE

July 10 at 1000 UTC or earlier.