It could literally boil/vaporise meters of water.
This is rough partial translation of article from member magazine of Finnish astronomical association. (I did it for one other forum)
Asteroid cuts huge hole through atmosphere and moment later strikes to ocean and bedrock under it. Hundred thousands cubic kilometers of rock
vaporises, melts or is blown away instantly. Part of vaporised material escapes to space before hole in atmosphere closes.
Shockwave causes extremely powerfull earthquakes all around the world and in atmosphere it "flattens" everything to distance of thousand kilometer.
Explosion also rises huge tsunamis with height about one kilometer.
Vaporised material creates huge fireball which rises/spreads to atmosphere and fireball's heat radiation burns everything within line of sight. Part
of fireball's material rises above atmosphere and rains down in following days all over the world in form of small meteorites. This fiery meteorite
shower heats up atmosphere causing ignition of everything which is compustible. Heat also vaporizes one meter layer of water from all oceans and boils
couple meters more. Nitrogen and oxygen combines in heated atmosphere causing world wide acid rains.
Ash from world wide fires and dust from impact prevents sun light and heat from getting to surface causing dark and cold ice age. After dust settles
carbon oxides produced by fires, methane and water vaporized in impact start extreme greenhouse effect wich in turn raises temperature much higher
than it was before impact.
Actually some years ago Astronomy magazine had an article in which there was about this hypercane-theory.
It said that air pressure in those could get as low as 500 millibars, compare that to lowest air pressures in hurricanes and other storms.
Well this one is from 1995:
Wind speeds 300 m/s... that makes even tornadoes look like gentle breeze.
Hurricane From Hell
There is ample evidence of a global firestorm at the time of the Chicxulub impact. Iridium-bearing clay in the boundary layer between the
Cretaceous Period (a time when dinosaurs roamed) and Tertiary Period (the subsequent geologic time frame when dinosaurs seem to have disappeared)
contains soot. www.space.com...
The quantity and composition of the soot corresponds to the burning of at least 50 percent of the world's forests. Although Hurdle's idea that
methane fires were responsible for this firestorm is plausible, there is another simpler explanation.
The Chicxulub impact would have launched millions of tons of rock into ballistic space flight. Over the following hour this debris would have
re-entered the Earth's atmosphere at high speed, causing millions of brilliant "shooting stars." The radiant heat from these meteors alone would
have been sufficient to ignite the trees around the world.
This idea is supported by the discovery of charcoal in tsunami deposits near the impact site. The best explanation may be that the trees were ignited
by radiant heat, then swamped soon after by the waves.
The shock wave from the impact would indeed have triggered massive earthquakes in the region and indirectly triggered other earthquakes around the
globe. A tsunami would have formed from the impact, which occurred in a shallow sea. The giant waves would also have been generated by the earthquakes
and undersea landslides triggered by the shock wave.
"Megawaves emanating from an impact site would circuit the earth at high speeds and cause worldwide disruption in the entire ocean in a single day,"
Hurdle and his colleagues wrote.
So dinosaurs, if they were not consumed in a firestorm, would have had to live through a torturous sequence of events -- from the barbecue to the
freezer, to a dip in acid and then a hothouse baking.
The debate continues on whether the Chicxulub impact caused the mass extinction at the end of the Cretaceous Period or whether it was one of a
sequence of disasters. The Deccan Traps of India are the remnants of a massive upwelling of molten rock from deep within the Earth 65 million years
ago. The toxic fumes and dust from the eruption have been put forward as a possible alternative cause of climate change that led to the extinction of
the dinosaurs. How an Asteroid Impact Causes
A possible link between impacts and volcanism became evident in 1974 when the Mariner 10 spacecraft flew past the innermost planet Mercury. The planet
was found to be covered with impact craters like the moon. One giant impact crater on Mercury was particularly interesting. Directly opposite the
impact point, on the other side of the planet (called the "antipodal point") was a region of highly disrupted terrain with no evidence of an impact.
The shock waves from the impact on one side of Mercury had traveled around the surface and met simultaneously at the antipodal point to create the
chaotic features. Similar features have since been detected on several moons of the giant planets.
Astronomer Duncan Steel has suggested that the same occurred with the Chicxulub impact and that the shock waves caused the Deccan Traps. Taking into
account millions of years of continental drift, this region would have been at the antipodal point to Mexico at the time of the impact. Although the
eruption may have contributed to the suffering, it now seems more likely that the Deccan Traps were just a consequence of the catastrophic initial
event, the Chicxulub impact.
Hunt for Oil Leads to Crater Linked to 'Great Dying'
Distance from Impact: 1000.00 km = 621.00 miles
Projectile Diameter: 20000.00 m = 65600.00 ft = 12.42 miles
Projectile Density: 3000 kg/m3
Impact Velocity: 20.00 km/s = 12.42 miles/s
Impact Angle: 70 degrees
Target Density: 2750 kg/m3
Target Type: Crystalline Rock
Energy: Energy before atmospheric entry: 2.51e+24 Joules = 6.00e+8 MegaTons TNT
Major Global Changes:
The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the Earth's rotation period or the tilt of its axis.
The impact does not shift the Earth's orbit noticeably.
Transient Crater Diameter: 125 km = 77.8 miles
Transient Crater Depth: 44.3 km = 27.5 miles
Final Crater Diameter: 236 km = 147 miles
Final Crater Depth: 1.53 km = 0.952 miles
The crater formed is a complex crater.
The volume of the target melted or vaporized is 22400 km3 = 5360 miles3
Roughly half the melt remains in the crater , where its average thickness is 1.82 km = 1.13 miles
Time for maximum radiation: 13.6 seconds after impact
Visible fireball radius: 194 km = 120 miles
The fireball appears 44 times larger than the sun
Thermal Exposure: 7.65e+7 Joules/m2
Duration of Irradiation: 353 seconds
Radiant flux (relative to the sun): 217
Effects of Thermal Radiation:
Much of the body suffers third degree burns
Deciduous trees ignite
The major seismic shaking will arrive at approximately 200 seconds.
Richter Scale Magnitude: 10.5 (This is greater than any earthquake in recorded history)
Mercalli Scale Intensity at a distance of 1000 km:
VI. Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.
VII. Damage negligible in buildings of good design and construction; slight to moderate in well-build ordinary structures; considerable damage in
poorly built or badly designed structures; some chimneys broken.
The ejecta will arrive approximately 494 seconds after the impact.
Average Ejecta Thickness: 2.56 m = 8.4 ft
Mean Fragment Diameter: 3.67 mm = 0.144 inches
The air blast will arrive at approximately 3030 seconds.
Peak Overpressure: 486000 Pa = 4.86 bars = 69 psi
Max wind velocity: 504 m/s = 1130 mph
Sound Intensity: 114 dB (May cause ear pain)
Multistory wall-bearing buildings will collapse.
Wood frame buildings will almost completely collapse.
Multistory steel-framed office-type buildings will suffer extreme frame distortion, incipient collapse.
Highway truss bridges will collapse.
Highway girder bridges will collapse.
Glass windows will shatter.
Cars and trucks will be largely displaced and grossly distorted and will require rebuilding before use.
Up to 90 percent of trees blown down; remainder stripped of branches and leaves.
(crater size is still too small)