It's Labor Day weekend, the unofficial end of summer.

That is always hard to accept. Somehow, September isn't the same. Before I accept the reality of cooler temperatures and longer nights, I want to savor the memory of the Jaguar XKR100 Convertible.

This slinky slab of automotive sex is a celebration of sorts. Jaguar has released 500 XKR100 coupes and 500 XKR100 convertibles worldwide to celebrate the centennial of the birth of Sir William Lyons, Jaguar's founder.

One feels he would approve of the XKR100 convertible, that purrs proudly with more than a hint of menace.

The V-8-powered, rear-wheel-drive XK8 debuted in 1996, with its super-charged stablemate, the XKR, debuting in 1998.

The XKR100 starts as an XKR. This is no bad thing.

There's no need for superlatives, as one look at an XKR is enough to set any enthusiast's heart aflutter. The XKR100, like the Model T, comes in only one color. But that's the extension of the Ford influence here.

The XKR100 can be distinguished from lesser kitties by its mammoth 20-inch BBS performance alloy wheels, red wheel centers with a ''growler'' Jaguar emblem, Brembo brakes and, of course, a mesh grille and louvered hood. A special red, black and silver bonnet badge completes the exterior differences.

Inside, aluminum trim is used for the foot pedals, door handles, instrument gauge accent and transmission selector. A Momo gear knob and steering wheel are leather-covered.

Leather Recaro seats grace the interior both front and rear. The wood trim completes the special touches with gray-stained bird's-eye maple trim. That little dose of performance enhances what is already an incredible motoring experience.

The engine is the same one used in the XKR, a supercharged version of Jaguar's AJ-V8. It produces 370 horsepower and is good for 0-60 mph in a mere 5.3 seconds in the convertible and 5.2 in the coupe. According to Jaguar, this is the fastest production car the company has ever built.

Needless to say, power from this little feline is ferocious, but ever so mannered in the Jaguar idiom. Like any classic Jaguar, the car feels better the harder you drive it. A five-speed automatic with Jaguar's J-gate shifter is the only transmission.

The automatic delivers instant shifts with a velvety smoothness, but purists will miss having a manual transmission option. Despite that, this Jag handles with the grace and agility one expects of a fine Grand Tourer. The ride is a bit firmer than the standard Jag, but this is due not only to the big wheels, but also a revised suspension.

Jaguar refined its Computer Active Technology Suspension (or CATS) to deliver a firmer ride and more direct ride feel. Springs and anti-roll bars were upgraded and the steering was recalibrated to be more taut.

The result is a ride fit for a truly memorable holiday weekend, even when it isn't one. The ability of this car is astounding, as enormously illegal speeds are too easy to enjoy.

If that should put you in over your head, Jaguar has you covered.

Anti-lock brakes, stability control, traction control and front and side airbags are all standard.

The Recaro seats seem larger than the ones Jaguar uses as standard fare, but they're also much more supportive, with aggressive side bolsters that do a great job of holding you in place during fast maneuvers. The leather-covered rear seat is best used for parcels.

While the cabin is tight, just as it is in every XK-Series Jaguar, it still has the same opulent feel. Sumptuous leather, fine wood and lots of buttons accent the interior. The buttons come from the fact that the car comes fully loaded.

A somewhat distracting DVD navigation system is standard. Ditto the premium sound system with changer, automatic climate control, trip computer, heated windshield and door mirrors, elec rochromatic rear-view mirrors, central locking, fog lamps and rain-sensing windshield wipers. The buttons on the audio system double as a car-phone keypad.

The convertible top lowers at the touch of a button. It is fully lined and has a glass rear window with defogger.

The XKR100 is a blast, pure and simple, yet one that only 250 Americans will have the chance to experience. At a retail price of $98,330, you won't find one on every corner.

But the XKR100 convertible is an incredible way to experience summer and its delights, even if it is at obscene rates of speed.