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 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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Quoting StormTracker2K:
Deniers about gulf weakness then read post 1269

Nobody is denying the Gulf weakness. We're denying the idea that the weakeness affecting the cyclone in 2 to 3 days like you were so adamantly shoving down our throats about an hour ago.
Member Since: July 6, 2010 Posts: 113 Comments: 32292
Quoting tropicfreak:


You mean TD 5


Hurricane is forecast to be S of Jamaica where a trough would pick it up if were going to.
Member Since: August 19, 2005 Posts: 5 Comments: 5450
000
WTNT35 KNHC 012036
TCPAT5

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

...TROPICAL DEPRESSION FORMS IN THE TROPICAL ATLANTIC EAST OF THE
WINDWARD ISLANDS...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...12.2N 49.0W
ABOUT 810 MI...1305 KM E OF THE WINDWARD ISLANDS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 18 MPH...30 KM/H
MINIMUM CENTRAL PRESSURE...1008 MB...29.77 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

THE GOVERNMENT OF BARBADOS HAS ISSUED A TROPICAL STORM WATCH FOR
BARBADOS...ST. VINCENT AND THE GRENADINES...AND DOMINICA.

THE GOVERNMENT OF ST. LUCIA HAS ISSUED A TROPICAL STORM WATCH FOR
ST. LUCIA.

THE GOVERNMENT OF FRANCE HAS ISSUED A TROPICAL STORM WATCH FOR
MARTINIQUE AND GUADELOUPE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* BARBADOS...ST. VINCENT AND THE GRENADINES...AND DOMINICA
* ST. LUCIA
* MARTINIQUE AND GUADELOUPE

INTERESTS ELSEWHERE IN THE LESSER ANTILLES SHOULD MONITOR THE
PROGRESS OF THIS SYSTEM.

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 48 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


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.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1008 MB...29.77 INCHES.


HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM CONDITIONS ARE POSSIBLE WITHIN THE WATCH AREA
ON FRIDAY.


NEXT ADVISORY
-------------
NEXT INTERMEDIATE ADVISORY...800 PM AST.
NEXT COMPLETE ADVISORY...1100 PM AST.

$$
FORECASTER PASCH
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Quoting mcluvincane:
What happened to the el nino trade winds that were supposed to rip thus thing apart once it got into the Caribbean

The tropical wave ahead of TD #5 disrupted them.
Member Since: July 6, 2010 Posts: 113 Comments: 32292
Deniers about gulf weakness then read post 1269
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So we have Tropical Depression#5 that will be a concern (maybe) for next week here in South Florida if any.But looking at the satellite presentation on the Atlantic Rainbow loop,it's my imagination or I can see our old friend the so called (Puerto Rico wave) getting it's act together?,it's taking a huge area,this might be something that we have to close watch in my opinion,maybe just some nasty weather for us for the weekend let's hope not more than that.
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Quoting mcluvincane:
What happened to the el nino trade winds that were supposed to rip thus thing apart once it got into the Caribbean



I don't know. =(.
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Quoting wunderkidcayman:
TD5


huh that funny same exact cone and time frame that we had for Hurricane Dean
Hurricane Dean


That is not a good track at all for us, it's the last thing we need here, now is the time to assess our plans & prepare whether it goes north or south of us, I suspect we'll get a some weather from it!
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1276. KEEPEROFTHEGATE (Mod)
Quoting tropicfreak:
Wunderkidcayman is probably flipping out right now.
he may have the paper bag out as we type
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Quoting GeorgiaStormz:
We broke chat now
No, I was just about to join, we are too excited with TD5.
Member Since: March 16, 2012 Posts: 127 Comments: 7951
1274. Patrap

Storm Relative 16km Geostationary Water Vapor Imagery

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Quoting GeorgiaStormz:
We broke chat now
We sure did...
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Okmulgee, Oklahoma (Airport)
Clear
115 °F
Clear
Humidity: 21%
Dew Point: 66 °F
Wind: 12 mph from the SSW
Pressure: 29.77 in (Falling)
Heat Index: 121 °F


Worse track possible for an August storm....meaning dangerous path

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CMC is doing a good job so far
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What happened to the el nino trade winds that were supposed to rip thus thing apart once it got into the Caribbean
Member Since: Posts: Comments:
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.

Read more at http://www.wunderground.com/tropical/at201205.disc .html#bUMHEA8xoXdYYTQc.99
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Quoting TropicalAnalystwx13:
So much for the unfavorable wind shear and trade winds.

They're not unfavorable but they're not super conducive either... If they were then we'd see the NHC forecasting a much stronger system with all the fuel (warm waters) out there.
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Could someone please post an image of the advisory?

TIA
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1265. pcola57
Not sure if this has been posted yet..
Edit: someone must have posted it so I will remove so more blog space can be utilized..

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We broke chat now
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1263. Patrap
Someone up in the Bain tower pulled da plug for a second me tinks.

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Quoting tropicfreak:
Wunderkidcayman is probably flipping out right now.
oh yeah he probably is and if this indeed becomes a hurricane his forecast would be right.
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Quoting stormpetrol:


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


You and me both.
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Well, that was weird...
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lol
Quoting TropicalAnalystwx13:
We broke the blog. XD
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1257. Patrap
..meh'

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So much for the unfavorable wind shear and trade winds.
Member Since: July 6, 2010 Posts: 113 Comments: 32292


This will probably change, but I don't like this initial track at all :(
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lol
Quoting ProgressivePulse:
Did the blog die?
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TD5


huh that funny same exact cone and time frame that we had for Hurricane Dean
Hurricane Dean
Member Since: June 13, 2009 Posts: 2 Comments: 12168
If 05L can remain south of 18˚N before reaching 79˚W, I'd say category 2 is probable. Obviously we're still a ways away from this cyclone reaching the western Caribbean, so it's nothing but speculation at this point.
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We broke the blog. XD
Member Since: July 6, 2010 Posts: 113 Comments: 32292
1248. Grothar
Quoting KEEPEROFTHEGATE:
looks like the doc will have to do an update


I told him at least 5 times it would be a depression on Wednesday, but he never listens to me.
Member Since: July 17, 2009 Posts: 71 Comments: 26529
1247. Patrap
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Quoting HurricaneDevo:


I like the intentional misspelling! Double entendre.


I'm surprised that no one got the joke but you. :P
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THIS IS A DANGEROUS STORM
a path to the Caribbean and then to the Gulf of Mexico....
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Wunderkidcayman is probably flipping out right now.
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Quoting jeffs713:
Where were you during the recurring discussions about the farmer's almanac's predictions for this year?


LOL! It actually said C Gulf coast hurricane threat mid August. I posted that a few weeks ago. Thanks for the refresher on that.
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1242. Patrap
Everyone survived the server re-boot I see.

Cool.
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1241. bwi
Quoting CybrTeddy:
NHC is forecasting TD5 to become a Hurricane at the end of the forecast period.

About time we get a good Caribbean cruiser, haven't seen one since 2007. Though the idea of a intensifying Category 1 hurricane going through all that TCHP makes me shutter.


"shudder" or "shutter" actually, or both!
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1240. Grothar
Member Since: July 17, 2009 Posts: 71 Comments: 26529
I'm proud of me, my forecast last night
Only in the intensity fail


Member Since: June 20, 2012 Posts: 0 Comments: 2159
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
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Quoting HadesGodWyvern:
wow!

four cyclones in the world.. That sure is different for once.


I guess everyone is in shock, HGW
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Did the blog die?
Member Since: August 19, 2005 Posts: 5 Comments: 5450

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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.