I have found more support for F3 Landspouts:
"From: "Jonathan Triggs" <jtriggs@USWCL.ARS.AG.GOV>
To: <WX-CHASE@listserv.uiuc.edu>
Sent: Friday, July 13, 2001 12:25 PM
Subject: Re: [WX-CHASE] Landspout Winds
> The discussion on landspouts v. tornadoes reminded me of an article
> written by a man that worked closely with Ted Fujita...
>
> Wakimoto, R.M., and J.W. Wilson, 1989: Non-supercell tornadoes. Monthly
> Weather Review, 117, 1113-1140.
>
> The article discussed how small areas of pre-existing circulations can
> be stretched and picked up by convective updrafts to form "non-supercell
> tornadoes." A big example of these conditions is the Denver and Front
> Range areas where there is a nearly persistent convergence boundary.
> When a tight area of positive vorticity becomes collocated with an
> updraft (e.g. cumulus cloud), the results can be explosive...
>
> The article also points out that landspouts can cause damage up to the
> F3 level. Also to note...they referred to the term "landspout" as the
> common expression, but they defined them as tornadoes not associated
> with a supercell.
>
> Jonathan Triggs"
http://ams.allenpress.com/perlserv/...175/1520-0493(1989)117<1113:NST>2.0.CO;2&ct=1
I checked the article and it says capabilities up to F2, but mentions two tornadoes they found matching the landspout definition and one was F3.