NEW YORK (

TheStreet

) -- Shares of

Fortinet

(FTNT) - Get Report

are soaring, after the company's initial public offering priced higher than expected.

The network security provider offered 12.5 million shares for $12.50, to rake in about $156.3 million. Fortinet previously expected for shares to price between $9 and $11 each.

Shares spiked up to 40% in their first morning of trading, and are currently changing hands at $16.48. Fortinet is on track to be the strongest IPO debut in 2009.

Existing shareholders are selling about 6.7 million shares, while the company is offering 5.8 million, leaving Fortinet with proceeds of $75.5 million.

Earlier in the week the company increased the size of the deal by 500,000 shares to meet the strong demand.

Also coming to market this week are

Archipelago Learning

and

Cloud Peak Energy

.

Archipelago provides Web-based educational testing and study aid to students in kindergarten through 12th grade. The deal could garner as much as $106.3 million or more if underwriters exercise their overallotment options.

The company expects the offering to price between$15 and $17.

Cloud Peak Energy, which oversees mines out West, is looking for shares to price in the range of $16 and $18 a share. It will offer 35.2 million shares and expects to raise $491.6 million after expenses.

Last week, two retailers,

Dollar General

(DG) - Get Report

and

rue21

(RUE)

,

completed their IPOs

.

So far the

fourth quarter has been the biggest for IPOs

since the first quarter last year. The fourth quarter has already seen IPOs from

Banco Santander Brasil

(BSBR) - Get Report

,

Verisk Analytics

(VRSK) - Get Report

,

Hyatt Hotels

(H) - Get Report

,

Vitamin Shoppe

(VSI) - Get Report

and

Dole Foods

(DOLE)

, among others.

-- Reported by Jeanine Poggi in New York

Follow TheStreet.com on

Twitter

and become a fan on

Facebook.

Copyright 2009 TheStreet.com Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed. AP contributed to this report.