DFW AFD very interesting..

[djtil]

Implied questioning of NW turn, along with the chance of getting cutoff among the better points.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
401 PM CDT WED SEP 21 2005

.DISCUSSION...
400 PM CDT

500MB HEIGHTS ON NEW 18Z SOUNDING VIRTUALLY UNCHANGED FROM 12Z.
TEMPS MAY REACH 100F SOME AREAS THIS AFTERNOON AS RIDGE REMAINS
STRONGEST OF THE SEASON. DESPITE PREDICTED WEAKENING OF RIDGE...
HIGH TEMPS MAY BE EVEN HIGHER THURSDAY AS RITA SUBSIDENCE ZONE
APPROACHES. EXPECT RECORD HIGHS THURSDAY...AS RECORD HIGHS ARE
ONLY 98F BOTH DFW AND WACO.

HURRICANE RITA NOW CATEGORY 5...165MPH...AMONG THE STRONGEST GULF
HURRICANES EVER RECORDED. APPEARS TO BE MAKING JOG TO NORTH...BUT
LIKELY ONLY TYPICAL WOBBLE OF EXTREME HURRICANES. SHOULD BOUNCE
BACK SOUTH WITH STRENGTH OF RIDGE...AND EXPECT GENERAL WESTWARD
MOVEMENT TO CONTINUE AS RIDGE REMAINS STRONG. MODELS STILL IN
REMARKABLE AGREEMENT WITH RAPID HEIGHT FALLS OVER TEXAS...BREAKING
RIDGE DOWN AND SHUNTING IT EAST...BUT THIS APPEARS TO BE HAPPENING
MORE SLOWLY THAN ADVERTISED. EVENTUAL TURN NORTH PER TPC FORECAST
WILL REQUIRE SUCH A RAPID WEAKENING...AND CURRENT FORECAST PACKAGE
WILL REMAIN IN AGREEMENT WITH MODELS AND TPC PROJECTIONS.

EVEN SLIGHT CHANGES TO POINT OF LANDFALL AND TRACK NORTH ACROSS
TEXAS WILL HAVE ENORMOUS EFFECT ON FORECAST FOR THE WEEKEND.
KEEPING LIKELY POPS CENTRAL AND EAST...AS WEST SIDE OF STORM WILL
SUFFER FROM ENTRAINMENT OF DRY AIR FROM THE NORTH. EAST-WEST
PRECIP GRADIENT COULD BE VERY DRAMATIC...BUT WILL SHOW
UNCERTAINTY WITH CHANCE POPS.

CURRENT FORECAST TRACK WILL ALLOW FOR SUSTAINED TROPICAL STORM
FORCE WINDS IN SOUTHERN ZONES SATURDAY AFTERNOON AND EVENING.
STRENGTH AND SPEED OF RITA MAY ALLOW SUSTAINED WINDS TO PENETRATE
FURTHER INLAND THAN IS USUALLY OBSERVED...BUT FRICTION WILL REDUCE
PEAK WINDS AND AREAL EXTENT. THUS...EXPECT WINDS TO BE 40 MPH AND
UNDER FROM I-20 CORRIDOR NORTHWARD IF DEPRESSION TRAVERSES CWA PER
TPC FORECAST. REGARDLESS...HIGHER WINDS WILL BE POSSIBLE IN
SQUALLS AND EMBEDDED THUNDERSTORMS.

EXTENDED MODELS NOW IN FRIGHTENINGLY GOOD AGREEMENT WITH CUTTING
OFF LOW ALONG WEST COAST. THIS WOULD CONFINE WESTERLIES TO
NORTHERN STATES...EFFECTIVELY CUTTING OFF RITA ESCAPE ROUTE TO THE
NORTHEAST. IF THIS SCENARIO PLAYS OUT...REMNANTS OF RITA MAY
LINGER IN NORTH TEXAS THROUGH TUESDAY. PWATS WOULD REMAIN
EXTRAORDINARY...AND TREMENDOUS STORM TOTALS COULD RESULT. TPC
FORECAST HOWEVER FAVORS EJECTING RITA NORTH QUICKLY. TOO MUCH
UNCERTAINTY NOW...BUT WILL KEEP POPS IN THROUGH TUESDAY NIGHT.

[canegrl04]

Being A North texan,this is very worrisome

[djtil]

based on the discussion and notes about the strong high...id be more worried if i was a corpus christian!!

but if it does turn....could be real rainy for a couple days.

[gboudx]

What I get from that discussion is that they have just about no clue what's going to happen in the next 3-6 days. There's an implied, "Stay tuned."

[TexasStooge]

I know we needed the rain, but dang!!!

[djtil]

What I get from that discussion is that they have just about no clue what's going to happen in the next 3-6 days

what i get is that they have an idea/clue....but its different than the NHCs.

[rainstorm]

many models indicate a stall over east central tx

[TexasStooge]

The NWS said North Texas will be expecting 4-6 inches of rain now. This is not good!!!!

[BReb]

Can someone tell me what this "500 mb heights" he's referring to is? I take it it's a barometric pressure reading of some kind. Is there a map online where I can follow what the "heights" are?

[gboudx]

The NWS said North Texas will be expecting 4-6 inches of rain now. This is not good!!!!

Actually, that's just what we need. Aren't we like 7-9 inches below normal so far this year?

[snoopj]

Yeah, but not all of it in a 48 hour period. Ground isn't going to absorb it that fast.

--snoopj

[gboudx]

Yeah, but not all of it in a 48 hour period. Ground isn't going to absorb it that fast.

--snoopj

Yeah, I know. But I'll take what we can get at this point. Some of it will get absorbed, the lakes will get a fresh supply of water, hopefully kill off some of the nasty algae that makes the water stink and taste bad.

[BReb]

This link would appear to answer my question about 500 mb heights- it's the height in feet or meters at which the air thins out enough to go down to 500 mb pressure.

http://www.atmo.arizona.edu/students/co ... 500mb.html

On a hot, high pressure day the air heats up and thus the height at which the pressure goes down to 500 mb is higher than on a cold day in which a low pressure trough is prevailing.

[Wthrman13]

This link would appear to answer my question about 500 mb heights- it's the height in feet or meters at which the air thins out enough to go down to 500 mb pressure.

http://www.atmo.arizona.edu/students/co ... 500mb.html

On a hot, high pressure day the air heats up and thus the height at which the pressure goes down to 500 mb is higher than on a cold day in which a low pressure trough is prevailing.

More or less correct when you consider cold-core lows, and warm-core highs, but in the case of a warm core low, such as a hurricane, the surface pressure and 500 mb heights in the center of the vortex are very low, yet the temperature at both levels is also warmer than the surroundings. The reason for this apparent paradox is that a warm core vortex contains a column of air in the center that is overall warmer than the surrounding air at all (or at least most) levels, all the way to the top of the troposphere. Because the whole column is warmer, particularly in the low-levels, it is also less dense, meaning that there is less mass in that column of air, than in columns of air surrounding the center, so the surface pressure is lower, and also the heights of various pressure surfaces, such as the 500 mb height.