Call traders are converging on Citigroup Inc. (NYSE:C - 35.85) today, with speculators gambling on more short-term upside for the financial stock. Around midday, C has already seen roughly 97,000 calls change hands -- about four times its average intraday call volume, and nearly three times the number of C puts exchanged.

Most active have been the January 37 and weekly 36-strike calls, which have seen around 12,100 and 11,700 contracts traded, respectively. Implied volatility on the back-month call was last seen higher, and volume has exceeded open interest at the weekly call, both signs of new initiations. Plus, the majority of the calls have crossed on the ask side, suggesting they were bought.

By purchasing the calls to open, the buyers are expecting C to surmount the respective strikes within the options' lifetimes. More specifically, the volume-weighted average price (VWAP) of the January 37 calls is $1.03, meaning the buyers will profit if C topples the $38.03 marker (strike plus average premium paid) within the next couple of months. Meanwhile, the VWAP of the soon-to-expire weekly calls is $0.27, indicating that C needs to conquer the $36.27 level by the end of the week, in order for the buyers to reap a reward.

Broadening our sentiment scope, we find that today's appetite for bullish bets runs counter to the recent trend seen on the major options exchanges. On the International Securities Exchange (ISE), Chicago Board Options Exchange (CBOE), and NASDAQ OMX PHLX (PHLX), the stock's 10-day put/call volume ratio of 0.73 ranks in the 74th percentile of its annual range. In other words, option buyers have initiated bearish bets over bullish at a faster-than-usual clip during the past couple of weeks.

At last check, the shares of C have skyrocketed roughly 4.6% to wink at the $35.85 level -- in an area we're watching closely -- after the firm announced plans to cut 11,000 jobs, resulting in expected savings of as much as $1.1 billion a year. As such, C is on pace to end north of its 10-day and 20-day moving averages for the first time in nearly a month.