Sept 10 (Reuters) -Spot basis bids for corn and soybeans shipped by barge to the U.S. Gulf Coast weakened on Tuesday, while nearby FOB offers were scarce.

* Shippers are monitoring Tropical Storm Francine along the Gulf Coast, while low Mississippi River water levels continue to hamper barge shipments at the start of the corn and soy harvesting season.

* The U.S. Department of Agriculture is expected to report its first national update on the soy harvest in a weekly report on Sept. 16. Some states already reported progress, with harvest 24% complete in Arkansas and 2% complete in Missouri, according to USDA data released on Monday.

* China imported a record 12.14 million metric tons of soybeans in August, up 29% from a year earlier. The large arrivals swell an oversupply in the world's top soy buyer as a struggling economy weakens consumption of meat and dairy.

* FOB export offers for U.S. soy and corn at the Gulf are thin and hard to come into October and early November, a trader said.

* CIF bids for corn barges loaded in September were about 79 cents over Chicago Board of Trade December CZ24 futures, down 4 cents from Monday. October barges were bid at about 81 cents over futures, down a penny.

* FOB Gulf export premiums for corn shipped in November were about 110 cents over CBOT December futures, up 3 cents.

* CIF soy barges loaded in September were bid at 72 cents over CBOT November soybean SX24 futures, down 4 cents. October CIF soy barges were bid at 77 cents over futures, also down 4 cents.

* FOB export premiums for Gulf soybeans loaded in November, the earliest available slot, were about 117 cents over futures, up 2 cents.

Reporting by Tom Polansek; Editing by Krishna Chandra Eluri

For displays of CIF basis, click on the codes in brackets: U.S. CIF Gulf soybeans GRYM U.S. CIF Gulf corn GRYN U.S. CIF Gulf SRW wheat GRYO U.S. CIF Gulf HRW wheat GRYP
For displays of FOB basis, please click on the following codes in brackets: U.S. FOB Gulf corn GRZC U.S. FOB Gulf soybeans GRZD U.S. FOB Gulf SRW wheat GRZE U.S. FOB Gulf HRW wheat GRZF LINKS Corn prices page: cpurl://apps.cp./cms/?pageid=corn-cash-market
Wheat prices page: cpurl://apps.cp./cms/?pageid=wheat-cash-market
U.S. barge freight BG/US
U.S. export sales estimates USDA/EST
U.S. grain export summary GRA/U
Brazil soybean export prices SYBS
Brazil corn export prices SYBX
Argentina grain prices GRA/ARG
Russia grain prices GRA/RU