PDA

View Full Version : Possible Good News - Rain-Wise


ijsouth
05-24-2007, 08:03 PM
I tend to be a bit of a weather geek, and I like checking out the long-range forecasts, particularly as I get closer to another trip to the Smokies. Lately, with the lack of rain in the Southeast and these fires, I think we're all a bit concerned. Here is the latest national long-range forecast discussion:

http://www.cpc.ncep.noaa.gov/products/predictions/610day/fxus06.html

Here is a bit from that report, concerning the 6-10 day forecast:

THE GFS FORECAST WOULD BENEFIT THE
SOUTHEAST US GREATLY... USHERING IN MOIST AIR AND COOLER TEMPERATURES. THIS
WOULD CERTAINLY HELP MITIGATE THE DROUGHT AND WILD FIRE ISSUES OVER THE REGION.
THE OFFICIAL FORECAST WILL BE SOMEWHAT OF A COMPROMISE... MODERATING THE GFS
PATTERN SOMEWHAT... BUT AGREEING ON THE BELOW NORMAL TEMPERATURES AND ABOVE
NORMAL PRECIPITATION AMOUNTS FOR THE SOUTHEAST


The 8-14 day forecast is also calling for above-average chances for rain for the Southeast. While this is a long-term forecast, and thus subject to change, it is the first piece of encouraging news concerning the drought I've seen. We've been getting rain the last few days down here - very much the typical summertime pattern, so the moisture isn't far away from the mountains. We just need that stubborn high to pull out to sea, and then the moisture from the gulf will spread northward.

Giantfish
05-24-2007, 10:42 PM
Does that mean rain or no rain?? You seem to know alot about weather, so how do you find out about the weather if your in the middle of a stream fishin? Any signs? I know alot but I don't know that. I hope, I love the GSMNP, and all this warming is slowing it down. Come Rain Come! But with little acid please!

Giantfish

ijsouth
05-24-2007, 10:58 PM
All it means is that the computer models are pointing to a change in the pattern. Right now, the Southeast is dominated by high pressure centered over the Atlantic. In the warmer months, high pressure compresses and heats the air, forcing it downwards; as it sinks, it continues to warm and, most significantly, dry out. This supresses thunderstorm formation, which is what we're seeing now.

Here in Louisiana, we are beyond the western edge of this high pressure; therefore, we've had rain the past few days, along with persistent southeast winds, from around the perimeter of the high. Lake Ponchartrain is very high right now, with all the water being piled in from the gulf. The models are predicting this high to shift to the east, to be replaced with a trough of low pressure over the Southeast. Lower pressures will permit convection (the lifting of water vapor to higher altitudes, where it can cool and condense as rain). Now, does that mean it will rain all day, everywhere, on a specific day? No, it doesn't...it's just the overall trend. If I had to place a bet, I would say that there will be more scattered thunderstorms, particularly in the mountains, which tend to uplift air anyway. It also doesn't mean that the drought is over; but it might mean at least a break in these dry conditions.

And yes, I was a meteorology student at one time...;)

russ
05-25-2007, 08:15 AM
Giantfish remember this little rhyme the next time you are getting ready to go fishing early n the morning. "Red sky at night, sailor's delight; red sky in morning, sailors take warning." It means if the sun set looks really red, then you're going to have 12 hours of clear weather (if you can see the sun set until it is really red, then there aren't alot of clouds over the horizin. If you see a lot of red clouds in the morning then it is going to rain in the next 12 hours.

Rog 1
05-25-2007, 08:51 AM
That usually works unless you're under a cloud of smoke from forest fires to the east and the sun stays red all day long....

russ
05-25-2007, 09:02 AM
You've got a good point there.

Giantfish, here's the only reliable weather forecast for on stream that you need. If you see a wall of water coming from up stream towards you, then it is raining higher up on the mountain. If you see thunderclouds over your head, then it may start raining soon. And if you are catching a bunch of fish then the lightning will start and run you off the water but if you're not catching anything but trees then it will be a blue bird day all day long.

ijsouth
05-25-2007, 11:20 PM
Update on the long range forecast:

DOWNSTREAM THE MODELS GENERALLY AGREE MORE
ON THE 500 MB HEIGHT PATTERN THAN YESTERDAY. THE GFS PREDICTS THAT THE
NORTHERN AND SOUTHERN STREAMS WILL PHASE... WITH A MODERATE TROUGH AXIS
CENTERED OVER THE MISSISSIPPI RIVER VALLEY. THE ECMWF MEANWHILE FORECASTS MORE
PHASING OF THE NORTHERN AND SOUTHERN STREAMS THAN IT DID YESTERDAY... AND A
MORE AMPLIFIED RIDGE-TROUGH PATTERN OVER THE CONUS. THESE FORECASTS WOULD
BENEFIT THE SOUTHEAST US GREATLY... USHERING IN MOIST AIR AND COOLER
TEMPERATURES. THIS WOULD CERTAINLY HELP MITIGATE THE DROUGHT AND WILD FIRE
ISSUES OVER THE REGION. THE OFFICIAL FORECAST WILL STILL MODERATE THE GFS
PATTERN SOMEWHAT... BUT LEANING EVEN MORE TOWARDS THE GFS ENSEMBLE MEAN
FORECASTS. BELOW NORMAL TEMPERATURES AND ABOVE NORMAL PRECIPITATION AMOUNTS
ARE FORECAST FOR MUCH OF THE EASTERN CONUS… INCLUDING THE GREAT PLAINS… THE
MISSISSIPPI VALLEY… THE EASTERN GREAT LAKES AND THE ATLANTIC COAST REGIONS.

What does this mean? It means that the two computer models mentioned, which yesterday were a bit at odds with one another, now tend to agree - the high will move out, and there will be a trough over the eastern U.S.; now, how much rain will fall is an open question, but it certainly will be better odds than now.

This weekend will be very dry - it noticably dried up around here today, but it looks like relief may be on the way.

ijsouth
05-26-2007, 06:46 PM
Another update...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
306 PM EDT SAT MAY 26 2007

.SHORT TERM (TONIGHT AND TOMORROW)...
A FEW SHOWERS HAVE DEVELOPED IN THE HIGHER ELEVATIONS OF NE TN...SW
VA...AND THE SMOKIES. THEIR MOVEMENT DOES APPEAR TO BE SLOWLY TO THE
EAST IN A WEAK STEERING FLOW...SO EXPECT THAT THEY WILL REMAIN
CONFINED TO THE MOUNTAINS. WILL INCLUDE A MENTION OF ISOLATED
SHOWERS AND THUNDERSTORMS IN THESE AREAS AND IN THE NORTHERN
PLATEAU. THE RIDGE OF HIGH PRESSURE OVER THE AREA TODAY WILL SHIFT
SLIGHTLY TO THE EAST. THIS MAY HELP CREATE A MORE SOUTHWESTERLY FLOW
AND ALLOW HIGHER DEWPOINTS TO ADVECT INTO THE AREA. MODELS SHOW A
LITTLE MORE INSTABILITY TOMORROW AS WELL...SO WILL INCLUDE A SLIGHT
CHANCE POP IN THE MOUNTAINS...NE TN...SW VA...AND NORTHERN PLATEAU
IN THE AFTERNOON. HIGH TEMPERATURES FOR THE PAST FEW DAYS HAVE
VERIFIED HIGHER THAN MOS GUIDANCE...LIKELY DUE TO THE DRY
CONDITIONS...SO WENT WITH HIGHS TOMORROW ABOVE MOS...BETWEEN 85 AND
90 OUTSIDE THE HIGHER ELEVATIONS.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)...THROUGH THE MIDDLE OF
NEXT WEEK SURFACE AND UPPER RIDGE WILL REMAIN FIRM ACROSS THE
SOUTHEAST UNITED STATES. AN UPPER TROUGH MOVING ACROSS THE NORTHERN
GREAT LAKES INTO FAR NORTHEAST UNITED STATES SUNDAY AND MONDAY WILL
PULL A COLD FRONT INTO THE SOUTHERN OHIO VALLEY/CENTRAL
APPALACHIANS. DUE TO THE PROXIMITY OF THE FRONT AND ASSOCIATED
HIGHER LOW LEVEL MOISTURE-CAPES...ISOLATED TO SCATTERED DIURNAL
CONVECTION IS POSSIBLE FOR SOUTHWEST VIRGINIA-NORTHEAST TENNESSEE-
NORTHERN PLATEAU BOTH MONDAY AND TUESDAY. ELSEWHERE...LITTLE TO NO
CHANCE OF CONVECTION.

THE GFS AND ECMWF MODELS AGREE WITH A MORE SUBSTANTIAL UPPER TROUGH
MOVING INTO THE EASTERN HALF OF THE NATION FOR LATE NEXT WEEK. COLD
FRONT IS PROGGED TO MOVE INTO THE FORECAST AREA FOR FRIDAY...SO HAVE
INCREASED POPS TO CHANCE AREA-WIDE. LATER SHIFTS WOULD NEED TO UP
POPS ONCE TIMING OF FROPA IS MORE CERTAIN.

Looking better and better for rain late next week - there's even a chance of a stray shower this weekend.

ijsouth
05-27-2007, 06:07 PM
And yet another update:

FOR THURSDAY AND FRIDAY...UPPER RIDGE BEGINS TO BREAK DOWN AHEAD OF
UPPER TROUGH MOVING ACROSS THE NORTHERN PLAINS TOWARD THE GREAT
LAKES. HAVE INCLUDE A SLIGHT POPS FOR THE WESTERN AREAS THURSDAY AND
AREA-WIDE FRIDAY.

FOR SATURDAY AND SUNDAY..UPPER TROUGH MOVES ACROSS THE GREAT LAKES
INTO THE NORTHEAST UNITED STATES WITH ASSOCIATED COLD FRONT TRAILING
SOUTHWEST TOWARD THE TENNESSEE VALLEY. WILL INCLUDE CHANCE POPS FOR
THE WEEKEND AS FRONT MOVES SLOWLY EAST ACROSS THE TENNESSEE VALLEY.

ijsouth
05-28-2007, 07:45 PM
The latest...not quite as optimistic:

.LONG TERM (TUESDAY NIGHT THROUGH MONDAY)...A BERMUDA HIGH ALONG THE
ATLANTIC COAST WILL COMBINE WITH A STRENGTHENING UPPER-LEVEL RIDGE
TO PRODUCE DRY CONDITIONS ACROSS THE FORECAST AREA THROUGH MOST OF
THE WEEK. SOME ISOLATED CONVECTION MAY BE POSSIBLE ACROSS THE
MOUNTAINS LATER THIS WEEK AS MOISTURE SLOWLY INCREASES. HOWEVER...
LAYER OF MOISTURE APPEARS RATHER SHALLOW ON MODEL SOUNDINGS...SO AM
NOT TOO OPTIMISTIC ABOUT RAIN CHANCES UNTIL THE WEEKEND WHEN A WEAK
COLD FRONT APPROACHES. LATEST GFS MODEL RUN CONTINUES TO SLOW DOWN
THE EASTWARD PROGRESSION OF THIS COLD FRONT...AND AM LEFT WONDERING
IF THE FRONT WILL EVER ARRIVE. WILL PLAN TO KEEP SLIGHTLY HIGHER
POPS IN THE FORECAST FOR THE WEEKEND...AS THE UPPER RIDGE IS PROGGED
TO WEAKEN WHICH SHOULD ALLOW THE COLD FRONT TO SLOWLY APPROACH THE
FORECAST AREA. AS FOR TEMPS...WILL CONTINUE WITH A PERSISTENCE
FORECAST THROUGH FRIDAY...WITH SLIGHTLY LOWER TEMPS FOR THE WEEKEND
DUE TO AN EXPECTED INCREASE IN MOISTURE AND CLOUD COVER.

I did take a look at the radar, and the storm totals approached .6 of an inch in places in the park, including the area of that fire. Most of the rain was to the north and east.