Disturbance 99L more organized; record melting in Austrian Alps

By: Dr. Jeff Masters , 2:02 PM GMT on August 01, 2012

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A tropical wave (Invest 99L) near 11°N 47°W, about 1000 miles east of the Lesser Antilles Islands, is showing increasing organization, and has the potential to develop into a tropical depression today or tomorrow as it moves westward at 15 - 20 mph. Visible satellite loops show that the disturbance now has two respectable low-level spiral bands, one to the north and one to the south, and a moderate amount of heavy thunderstorms near the center. The thunderstorm activity has not changed much in intensity this morning. A well-defined surface circulation is not evident on satellite images, but last night's 8:30 pm EDT pass from the ASCAT satellite showed a broad, elongated center with light winds had formed. Water vapor satellite loops show that 99L has a reasonably moist environment, and the latest Saharan air layer analysis shows that the dry air from the Sahara is not present in large quantities over the central tropical Atlantic. WInd shear over the disturbance has increased some since Tuesday, and is now at the moderate level, 10 - 15 knots. Ocean temperatures are 28°C, (82°F) which is about 0.5°C above average for this time of year.


Figure 1. Morning satellite image of Invest 99L.


Figure 2. Vertical instability over the tropical Atlantic in 2012 (blue line) compared to average (black line.) The instability is plotted in °C, as a difference in temperature from near the surface to the upper atmosphere. Thunderstorms grow much more readily when vertical instability is high. Instability has been lower than average, due to an unusual amount of dry, sinking air in the atmosphere, reducing the potential for tropical storm formation. Image credit: NOAA/NESDIS/CIRA.

Forecast for 99L
Wind shear is expected to remain light to moderate, 5 - 15 knots, through Friday, ocean temperatures will remain near 28°C, and mid-level moisture will be a moderate 60 - 70%, according to the 8 am EDT run of the SHIPS model. The disturbance has gained a bit of latitude and is now at 11°N, which will help it leverage the Earth's spin more to acquire its own spin. These conditions are probably sufficient for 99L to become Tropical Depression Five, with Thursday being the most likely day for this to happen. However, the reliable computer models are not very eager to develop 99L, and none show it becoming a hurricane over the next five days. This is probably because the atmosphere over the tropical Atlantic is unusually stable for this time of year (Figure 2), with large-scale areas of dry, sinking air present. Climatologically, we see very few Cape Verdes-type hurricanes forming near the Lesser Antilles Islands this early in August, and I expect 99L will struggle at times over the next few days. This is particularly likely if 99L goes north of 13°N, where a band a high wind shear of 20 - 40 knots associated with the subtropical jet stream lies. At 8 am Wednesday, NHC gave 99L a 60% chance of developing into a tropical depression by Friday morning. Residents and visitors to the Lesser Antilles Islands should anticipate heavy rains and strong winds from 99L beginning to affect the islands as early as Friday morning. The long-range fate of 99L next week is uncertain, but a track west to west-northwest through the Caribbean is the most popular solution from the models.


Figure 3. Typhoon Saola (bottom) and Typhoon Damrey (top) perform a pincer maneuver on Shanghai, China in this MODIS photo from NASA's Terra satellite taken at 02 UTC August 1, 2012. Image credit: NASA.

Two typhoons headed towards China
In the Western Pacific, typhoon season is in full swing with two typhoons headed towards China. The more dangerous of the two is Category 2 Typhoon Saola, which is predicted to skirt the northern coast of Taiwan and hit mainland China 300 miles south of Shanghai on Friday as a Category 3 typhoon. Typhoon Damrey, a Category 1 storm located just south of Japan, is expected to hit China about 150 miles north of Shanghai on Thursday at Category 1 strength.

Extreme heat in Oklahoma
The withering heat in America's heartland continued on Tuesday, with the prize for most ridiculous heat a 113° temperature recorded in Chandler, Oklahoma. A close second: Tulsa hit 112°, just 3° below the city's all-time high of 115° set on August 10, 1936. The low temperature in Tulsa was 88° Tuesday morning, tying the record for warmest low temperature in city history set just the previous day. Six locations in Oklahoma hit 112° or hotter Tuesday, and the forecast calls for highs near 112° again today over portions of Oklahoma.

Extreme dryness in the Central U.S.
A few final tallies for July precipitation are in, and several U.S. cities in the heart of the drought region set new records for driest July:

Joplin, MO: 0.00" (ties record set in 1946)
Springfield, MO: 0.32" (previous record 0.33" in 1953)
Sioux Falls, SD: 0.24" (previous record, 0.24" in 1947, normal is 3.09")

Record early snow melt in the Austrian Alps
One of the longest meteorological data records at high altitude comes from Sonnblick, Austria, on a mountaintop in the Alps with an elevation of 3106 meters (10,200 feet.) The observatory typically sees maximum snow depths of 3 - 4 meters (10 - 13 feet) during winter. According to weather records researcher Maximiliano Herrera, the snow had never completely melted at Sonnblick until the summer of 1992. Complete snow melt did not happen again until August 12, 2003, and has happened an average of once every two years since then--but always in September. Yesterday, on July 31, the snow completely melted at Sonnblick, the earliest melting since record keeping began in 1886. It's been an exceptionally hot summer in Austria, which experienced its 6th warmest June since record keeping began in 1767. Sonnblick Observatory recorded its all-time warmest temperature of 15.3°C (60°F) on June 30. Vienna hit 37.7°C (100°F) that day--the hottest temperature ever measured in June in Austria. Note that the two mountains in the Alps with long climate records, Saentis in Switzerland and Zugspitze in Germany, beat their records for earliest melting last year in 2011 (Saentis beat the previous record of 2003, and Zugspitze tied the record set in 2003.)


Figure 4. The Sonnblick Observatory in Austria on April 26, 2010. Image credit: Michael Staudinger.

Jeff Masters

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1316. TomTaylor 5:09 PM EDT on August 01, 2012

Good anylysis on the ULL to the North as noted in the NHC discussion; the separation between it and pre-Ernesto may not be as much of an issue once the storm gets into the Western Caribbean hence the intensity increase at that point with the current official forecast.
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My god... I get wifi for the first time in days and TD 5 has formed! Wow!
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1334. Patrap
Quoting kmanislander:


You had to post those eh LOL. Hopefully it will avoid this area.


Check the Vintages, and the Ice, you know da drill well Kman.

Afternoon.
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12z CMC run reminds me a lot of Emily from last year.
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Quoting barbadosjulie:
Thanks Stormjunkie. My family and I in Barnados are watching this very closely


No problem, y'all stay safe and keep an eye on it. Things can change quickly in the tropics as I am sure you are well aware of.
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000
WTNT45 KNHC 012044
TCDAT5

TROPICAL DEPRESSION FIVE DISCUSSION NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL AL052012
500 PM AST WED AUG 01 2012

DURING THE DAY...VISIBLE SATELLITE IMAGES SHOWED THAT THE LOW-LEVEL
CIRCULATION OF THE LOW PRESSURE SYSTEM TO THE EAST OF
THE WINDWARD ISLANDS HAS BECOME BETTER DEFINED. DEEP CONVECTION
HAS PULSED A BIT...AND IS SOMEWHAT LACKING OVER THE NORTHERN PART
OF THE CIRCULATION. HOWEVER THE SYSTEM HAS NOW ACQUIRED SUFFICIENT
ORGANIZATION TO BE CLASSIFIED AS A TROPICAL DEPRESSION. THE
INITIAL WIND SPEED IS SET AT 30 KT IN ACCORDANCE WITH DVORAK
ESTIMATES FROM TAFB AND SAB. FORECASTING INTENSITY CHANGE IS
ALWAYS A CHALLENGE...AND IS PARTICULARLY TRUE IN THIS CASE.
MODERATE VERTICAL SHEAR...ASSOCIATED WITH A LARGE UPPER-LEVEL LOW
TO THE NORTH OF THE DEPRESSION...IS LIKELY TO AFFECT THE SYSTEM FOR

THE NEXT COUPLE OF DAYS. THUS ONLY SLOW STRENGTHENING IS
ANTICIPATED DURING THE FIRST HALF OF THE FORECAST PERIOD. LATER
ON...THE INTENSITY FORECAST UNCERTAINTY INCREASES. OUR BEST TWO
GLOBAL MODELS ARE AT ODDS AS TO HOW THE SYSTEM WILL EVOLVE AS IT

MOVES OVER THE CARIBBEAN. THE GFS FORECASTS THE UPPER-LEVEL
ENVIRONMENT TO BECOME QUITE CONDUCIVE FOR STRENGTHENING BY THE END
OF THE FORECAST PERIOD...WHEREAS THE ECMWF MODEL SHOWS THE SYSTEM
DEGENERATING INTO A TROPICAL WAVE. THE OFFICIAL FORECAST LEANS
TOWARD TO THE GFS...BUT TIME WILL TELL.


THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 285/16. GLOBAL MODELS
DEPICT A STRONG MID-TROPOSPHERIC ANTICYCLONE TO THE NORTH OF THE
TROPICAL CYCLONE FOR THE NEXT SEVERAL DAYS. THIS STEERING PATTERN
SHOULD CAUSE A WEST-NORTHWESTWARD TO WESTWARD MOTION AT ABOUT THE
SAME SPEED THROUGH MUCH OF THE FORECAST PERIOD. A WEAKNESS OVER
THE GULF OF MEXICO COULD CAUSE SOME SLOWING AND BIT OF A
NORTHWESTWARD TURN LATE IN THE PERIOD. THE COMPUTER MODELS ARE IN
GOOD AGREEMENT...AND THE NHC TRACK FORECAST IS NOT FAR FROM THE
MODEL CONSENSUS.



FORECAST POSITIONS AND MAX WINDS

INIT 01/2100Z 12.2N 49.0W 30 KT 35 MPH
12H 02/0600Z 12.7N 51.3W 40 KT 45 MPH
24H 02/1800Z 13.3N 54.5W 45 KT 50 MPH
36H 03/0600Z 13.8N 57.7W 50 KT 60 MPH
48H 03/1800Z 14.4N 60.9W 55 KT 65 MPH
72H 04/1800Z 15.5N 67.0W 55 KT 65 MPH
96H 05/1800Z 16.5N 73.0W 60 KT 70 MPH
120H 06/1800Z 17.5N 78.0W 65 KT 75 MPH

$$
FORECASTER PASCH/BLAKE

This is a special System, even the noaa has lot uncertain in the intensity.......with this system everything can happen
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1330. Patrap
RainbowTop show's the shear impingement well.



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Quoting Patrap:





You had to post those eh LOL. Hopefully it will avoid this area.
Member Since: August 19, 2006 Posts: 0 Comments: 15847
Quoting ackee:
poll TD#5 GFS VS THE ECMWF which model soltion do u think have a better handle on TD#5 right now ?


They looked pretty similar to me except at the end?
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Quoting nofailsafe:
The CPC forecasts above average probabilities for rainfall during the 8-14 day period over the north and northwestern gulf coast. Sure hope that's just from the ridge backing down...



That aint good
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Link
Quoting 19N81W:
where did you see that they have called it td 5?
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Quoting ackee:
poll TD#5 GFS VS THE ECMWF which model soltion do u think have a better handle on TD#5 right now ?


They are actually very similar right now if I am not mistaken. The ECMWF just runs out further.
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1324. KEEPEROFTHEGATE (Mod)
Quoting Grothar:


I told him at least 5 times it would be a depression on Wednesday, but he never listens to me.


more will follow
this is not the only one
we may have 3 for the price of one
things are going to get a little intense
over the next week or so
moms got a lot to do over the next 44 days
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hmm I am not the only one to say it people
(WEST-NORTHWESTWARD TO WESTWARD MOTION)

DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 500 PM AST...2100 UTC...THE CENTER OF TROPICAL DEPRESSION FIVE
WAS LOCATED NEAR LATITUDE 12.2 NORTH...LONGITUDE 49.0 WEST. THE
DEPRESSION IS MOVING TOWARD THE WEST-NORTHWEST NEAR 18 MPH...30
KM/H...AND A WEST-NORTHWESTWARD TO WESTWARD MOTION AT ABOUT THE SAME
FORWARD SPEED IS EXPECTED OVER THE NEXT 48
HOURS.
ON THE FORECAST
TRACK...THE CENTER OF THE TROPICAL CYCLONE SHOULD BE NEAR THE
WINDWARD ISLANDS ON FRIDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/H...WITH HIGHER
GUSTS. SOME STRENGTHENING IS FORECAST DURING THE NEXT 48 HOURS...
AND THE DEPRESSION COULD BECOME A TROPICAL STORM TONIGHT OR ON
THURSDAY.
Member Since: June 13, 2009 Posts: 2 Comments: 12372
Quoting ackee:
poll TD#5 GFS VS THE ECMWF which model soltion do u think have a better handle on TD#5 right now ?

GFS
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The CPC forecasts above average probabilities for rainfall during the 8-14 day period over the north and northwestern gulf coast. Sure hope that's just from the ridge backing down...

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Thanks Stormjunkie. My family and I in Barnados are watching this very closely
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Quoting StormTracker2K:



Read post 1269 from the NHC. This is what I was trying to tell people on this blog but nobody was understanding I guess.


Your preaching to the choir here.

1169. ProgressivePulse 8:36 PM GMT on August 01, 2012 +1
Pretty confident myself in a track somewhere around Jamaica. From that point either the trough gets it and TD5 turns NW to N or it misses and TD5 continues off to the WNW.
Action: Quote | Modify Comment
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1317. Patrap
We look for model trends the next 48, then Consensus downstream.


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Satellite imagery and CIMSS analysis also shows the mid level circulation and low level circulation are slightly tilted with height, as a result of the convective mass being displaced to the SE. The ULL/TUTT feature to the north is limiting divergence/outflow to the NW and providing some shear out of the NW. There is also drier and dustier air to the north and out ahead of the storm. Both of these features are acting to limit convection to the NW, favor it to the SE, and is also why we are seeing parts of the circulation exposed in this area. These issues will follow the storm west, however, they are not significantly detrimental so we could see a moderate TS by the time this reaches the Caribbean...so long as the ULL keeps it's distance so shear remains light and the storm can become better stacked. If the ULL stays nearby inflicting stronger shear and further limiting upper divergence to the NW, then don't expect anything more than a weak TS.


Total Precipitable Water




ECMWF Dust Analysis at 42hrs (0z run from yesterday is shown)




Intensity after entering the Caribbean is hard to predict. The upper level environment arguably plays the largest role in determining intensification of a storm and unfortunately the models we have now are very poor at predicting the upper level environment. However a stronger low level pressure gradient in the east Caribbean should weaken or at least keep the storm weak until it reaches the western Caribbean.
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Quoting barbadosjulie:
Can anyone tell me how big TD5 is?


Right now, and what the models are calling for down the road is a fairly small storm in size.
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1314. ncstorm
I can count on one hand how many of yall have been right on this storm so far..

trade winds
its going south
tropical storm
its dying
NHC should classify it



the path will continue to shift guys with each suite of model runs..just sit back and enjoy the ride..
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1313. ackee
poll TD#5 GFS VS THE ECMWF which model soltion do u think have a better handle on TD#5 right now ?
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1312. Patrap
Curtain Level is

Chartreuse
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Quoting StormTracker2K:


I think you guys may want to watch this closely as I really feel A New Orleans to FL Panhandle threat is possible.


Lol. I hope you're wrong. :-)
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Quoting Patrap:





Basically untouched for several years now. Not good folks.
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1309. Patrap
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THE OFFICIAL FORECAST LEANS TOWARD TO THE GFS...BUT TIME WILL TELL.

Best comment in the discussion; as Dr. M noted several weeks ago with Debby, "The models are not gospel". Nice to see NHC acknowlege the current model divergence and end it on a human note..... :)
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I think we all on the blog agree this will stay south or an extreme case graze the main island chains and stay in the Caribbean. Exactly where nobody knows. All interests in Caribbean are now in high alert first and foremost.
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Quoting MississippiWx:


It slowed in the models as well and turned a bit to the northwest only to keep going WNW until landfall because of the westerlies never breaking down completely.


I think you guys may want to watch this closely as I really feel A New Orleans to FL Panhandle threat is possible.
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Can anyone tell me how big TD5 is?
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1304. LargoFl
..and the wave down by PR..........................Tropical wave moving toward Florida
A tropical wave is also moving toward the state near Hispaniola. The wave is expected to move over the state this weekend.
"It's a very vigorous system and flares up from time to time. It will very likely head toward Florida," Clay said.
The wave will bring increased rain chances through the weekend, but is not expected to become a tropical system.
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1303. Patrap



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1302. KEEPEROFTHEGATE (Mod)
Quoting Patrap:
rocket fuel for the rocket to come
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Quoting tropicfreak:
Wunderkidcayman is probably flipping out right now.


Probably had to change his underwear five times in the past 20 minutes.
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Quoting StormTracker2K:



Read post 1269 from the NHC. This is what I was trying to tell people on this blog but nobody was understanding I guess.


You're using that to your advantage a little too much. Unlike you, the NHC is not predicting a landfall in Eastern Gulf.
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1299. Patrap
But sometimes, u get what you need, aahhh, yeah
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Quoting TropicalAnalystwx13:

Nobody is denying the Gulf weakness. We're denying the weakeness affecting the cyclone in 2 to 3 days like you were so adamantly pushing on us about an hour ago.


No where did I say in 2 to 3 days.
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Quoting allancalderini:
oh yeah he probably is and if this indeed becomes a hurricane his forecast would be right.

I have no idea what the hell you two are talking about

Quoting stormpetrol:


This will probably change, but I don't like this initial track at all :(

yeah further west don't really like that either
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Quoting RitaEvac:
NWS offices along the gulf coast will be scrambling to see what weakness or ridging is forecasted long term as this will have dire consequences down the road


You can bet the Gulfstream's will be flying the Gulf soon.
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Quoting Patrap:

Storm Relative 16km Geostationary Water Vapor Imagery



Hey Pat, you guys might want to watch this one. I think this is going to be big.
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Quoting StormTracker2K:
Deniers about gulf weakness then read post 1269


It slowed in the models as well and turned a bit to the northwest only to keep going WNW until landfall because of the westerlies never breaking down completely.
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1293. WxLogic
TD#5 came together rather quickly.
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WHO!!!! broke chat now!!!!!!!!!!!!!! lol
and is it going to FL????
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Blog overload???
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NWS offices along the gulf coast will be scrambling to see what weakness or ridging is forecasted long term as this will have dire consequences down the road
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1289. LargoFl
...Cat1 by monday
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Quoting ProgressivePulse:


Hurricane is forecast to be S of Jamaica where a trough would pick it up if were going to.



Read post 1269 from the NHC. This is what I was trying to tell people on this blog but nobody was understanding I guess.
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1287. wpb
Quoting Patrap:

Storm Relative 16km Geostationary Water Vapor Imagery

upper low to north will be problematic
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Quoting Grothar:


I told him at least 5 times it would be a depression on Wednesday, but he never listens to me.
you actually did Grothar good job XD :)
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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