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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Quoting LargoFl:
..I still say we need to watch that wave down by PR
Agree, with you skirting Puerto Rico, or over, then towards the Mona Canal and eastern,DR, very flat lands , wont do any harm to the circulation.
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Quoting TropicalAnalystwx13:
Significant?



Right now is tracking a CMC and NOGAPS believe it or not
Member Since: June 20, 2012 Posts: 0 Comments: 2150
Member Since: August 6, 2011 Posts: 4 Comments: 36847
Quoting TropicalAnalystwx13:
Significant?



Wow excellent graphic it illustrate its climb in latitude over the last couple of hours.
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......................................Saturday 2pm
Member Since: August 6, 2011 Posts: 4 Comments: 36847
Quoting Stormchaser2007:


Thats from 7am lol

ok can you post a newer version

can any post some microwave data for 99L as current as possible thanks
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Quoting nofailsafe:
Current 500mbar steering currents:



Of note: the ridge over Texas is in full force at the moment but is further west than in earlier analyses. It will be crucial to monitor its position over the next few days as this will play a deciding factor in what direction 99L ends up going. The highest likelihood of a strike I feel would be along the eastern coast of Mexico somewhere between Brownsville, TX and Tampico.


That ridge is what the GFS and Euro must be seeing and why they do not turn Ernesto north. This is not an uncommon track at all- we saw it in 2009. Florida is protected with this set up.
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yeah I was wondering how strong the Bermuda High is supposed to be in respect to the trough. One thing for sure is the water temps are warm!
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99L Short Floater - RGB Color Imagery Loop
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A clear WNW movement over the past six hours:

Link
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Quoting TropicalAnalystwx13:
Significant?



In addition to what SouthDade said, it also did detach from the ITCZ today.
Member Since: June 9, 2007 Posts: 4 Comments: 15776
Quoting Houstonweathergrl:
Nofail...thanks for that extensive explanation. I think I understand. I suppose timing is critical.


Yeah, timing is going to be critical here as it always is. Someone's gonna catch this thing, it's odd that the Gulf is shaped like a baseball glove...
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Quoting floridaboy14:
Folks! the EURO model finally develops 99L into a looks like a TD! it takes it into TEXAS :O


Can you post the 500mbar height charts for the two days before landfall?
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Quoting jeffs713:
I just don't see the CMC's solution. It is an outlier track-wise, and I don't see enough of a weakness early enough to pull it north of the Islands for that kind of a track. Later on, yes, but 2-3 days from now, not so much.
I think TD/TS will skirt south or over Puerto Rico,continuing WNW, towards the mona Canal ,,, and heading over flat land of Eastern Hispaniola towards the Southern Caicos...Why, because the weakness in the high in 2 0r 3 days when the system reaches the area...South Florida is at risk..
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Quoting TropicalAnalystwx13:
Significant?

I'm not sure that it has really turned to the North that much, but rather that bend is a reflection of estimating the center too far to the South over the past 24-36 hours.
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Quoting kshipre1:
maybe a wrong assumption on my part but I think some in here think 99L (possible future Ernesto) might recurve due to the trough?


Hard for me to ignore the Euro and GFS that take this West through the Caribbbean and all the way to Northern Mexico or Southern Texas.
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Current 500mbar steering currents:



Of note: the ridge over Texas is in full force at the moment but is further west than in earlier analyses. It will be crucial to monitor its position over the next few days as this will play a deciding factor in what direction 99L ends up going. The highest likelihood of a strike I feel would be along the eastern coast of Mexico somewhere between Brownsville, TX and Tampico.
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Expect 99L to cross 60W around between 14 and 15 degrees North.
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If it starts blowing up by 9-10pm...

Bag it and tag it.

Member Since: June 9, 2007 Posts: 4 Comments: 15776
Quoting TropicalAnalystwx13:
Significant?



No! Expected if you look at the steering pattern in the vicinity of 99L, and models are seeing this as well.
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...............................remember this morning, almost all of these models put it going into the gulf?...now look closely, is that 2 now making a turn over cuba
Member Since: August 6, 2011 Posts: 4 Comments: 36847
I'm late on this as I was caught by surprise by a storm that just came through here. But it's worth posting again anyway:

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 15N45W 13N47W...
TO A 1009 MB LOW PRESSURE CENTER THAT IS NEAR 11N47W.
NUMEROUS STRONG CONVECTIVE PRECIPITATION IS FROM 10N TO 12N BETWEEN 47W AND 51W.

BROKEN TO OVERCAST MULTILAYERED CLOUDS AND OTHER POSSIBLE RAINSHOWERS COVER THE AREA ELSEWHERE FROM 6N TO 16N BETWEEN 43W AND 52W.

ENVIRONMENTAL CONDITIONS ARE CONDUCIVE FOR TROPICAL CYCLONE FORMATION. IT IS POSSIBLE THAT THIS LOW PRESSURE CENTER MAY BECOME A TROPICAL DEPRESSION LATER TODAY OR TONIGHT.

THIS SYSTEM HAS A HIGH CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES WEST-NORTHWESTWARD 17 KT.

ANYONE WHO LIVES IN THE WINDWARD ISLANDS AND/OR WHO HAS INTERESTS IN THE WINDWARD ISLANDS SHOULD MONITOR THE PROGRESS OF THIS SYSTEM.

99L's gaining in latitude and attitude for the time being.
Member Since: July 11, 2006 Posts: 14 Comments: 11168
Quoting TropicalAnalystwx13:

Not attached.



You are right. It has detached itself over the past few hours.
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Quoting nigel20:
..I still say we need to watch that wave down by PR
Member Since: August 6, 2011 Posts: 4 Comments: 36847
Folks! the EURO model finally develops 99L into a looks like a TD! it takes it into TEXAS :O
Member Since: July 25, 2011 Posts: 0 Comments: 1102
Significant?

Member Since: July 6, 2010 Posts: 113 Comments: 31430
Quoting Drakoen:
Satellite imagery shows a well defined circulation, on the verge of becoming a tropical depression.

01/1745 UTC 12.0N 48.3W T2.0/2.0 99L -- Atlantic


Whats up dude, this is on the verge of being classified
however the path remains uncertain. It continues its climb up in latitude it might go straight over PR and north of the islands into the Bahamas and the SE US.
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maybe a wrong assumption on my part but I think some in here think 99L (possible future Ernesto) might recurve due to the trough?
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Quoting Stormchaser2007:


Thats from 7am lol

This is the new SSMI pass



Still stand by it.
Member Since: July 15, 2006 Posts: 17 Comments: 10159
Good to see you Drak!

Hope everythings well.
Member Since: June 9, 2007 Posts: 4 Comments: 15776
952. BDAwx
Quoting jeffs713:

In theory, yes, but the topography of Taiwan in relation to Saola doesn't lend itself much to that - Taiwan is to the SW of the center, meaning the circulation is piling up on the NW side of the island, with the mountains between to potentially negate the effect.

It is an interesting thought, though, and not one I'd personally dismiss.


Thanks for your thoughts :)
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So is this storm going to the west or to the east of FL 0.0?
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Quoting Drakoen:
Satellite imagery shows a well defined circulation, on the verge of becoming a tropical depression.

01/1745 UTC 12.0N 48.3W T2.0/2.0 99L -- Atlantic
Greetings.
Member Since: September 27, 2007 Posts: 1 Comments: 20489
Quoting robert88:
I have to admit 99L's presentation looks a lot better over the last couple of hours. They may wait to classify until recon gets in there tomorrow.


Its quickly organizing as we speak it already have good banding features and a ball of convection right over the center to lower pressures this could be a TD by 5pm.
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Nofail...thanks for that extensive explanation. I think I understand. I suppose timing is critical.
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Satellite imagery shows a well defined circulation, on the verge of becoming a tropical depression.

01/1745 UTC 12.0N 48.3W T2.0/2.0 99L -- Atlantic
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Quoting Tropicsweatherpr:
So far no renumber. I think they will wait to see how it does at dimin.

its goin get renumbered within 2-3 hours
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Quoting MississippiWx:
This is a tropical cyclone.



Thats from 7am lol

This is the new SSMI pass

Member Since: June 9, 2007 Posts: 4 Comments: 15776
Quoting jrweatherman:


Close but still attached to the ITCZ. Think we'll have a TD in the morning.

Not attached.

Member Since: July 6, 2010 Posts: 113 Comments: 31430
If and When things become more interesting, I would like to request bloggers to look at the other posts at least on the first page to avoid posting repeats of model-run charts. Don't think anyone wants to see the same charts 10 times and it also speeds up the webpage.
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I have to admit 99L's presentation looks a lot better over the last couple of hours. They may wait to classify until recon gets in there tomorrow.
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This is a tropical cyclone.

Member Since: July 15, 2006 Posts: 17 Comments: 10159
Quoting allancalderini:
this is a td imo looks better than some ts like danny and henri of 2009.


Close but still attached to the ITCZ. Think we'll have a TD in the morning.
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Quoting Hurricanes305:


Looks like its ready to explode with all that energy concealed in a ball of intense convection. TD by 11pm.

Agreed.
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Quoting nigel20:



Looks like its ready to explode with all that energy concealed in a ball of intense convection. TD by 11pm.
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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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