African tropical wave 99L has potential to develop

By: Dr. Jeff Masters , 3:10 PM GMT on July 30, 2012

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The first African tropical wave of 2012 with a potential to develop is Invest 99L, located in the Eastern Atlantic near 9°N 36°W, midway between the Lesser Antilles Islands and the coast of Africa. Visible satellite loops show a large area of the surrounding atmosphere has a pronounced counter-clockwise spin, though there is no surface circulation. The disturbance's heavy thunderstorm activity is pretty sparse, but appears to be slowly increasing. 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 lies well to the north of 99L. WInd shear over the disturbance is a light 5 - 10 knots, and ocean temperatures are 28°C, (82°F) which is well above the 26.5°C (80°F) threshold typically needed to allow formation of a tropical depression.


Figure 1. Morning satellite image of Invest 99L.

Forecast for 99L
Wind shear is expected to remain light for the next five days, and ocean temperatures will remain near 28°C, according to the 8 am EDT run of the SHIPS model. The disturbance is at 9°N, which is close enough to the Equator that the storm will have some difficultly getting spinning. Most of the models are showing some slow development of 99L, with the storm reaching the Lesser Antilles Islands on Saturday, August 3. NHC gave 99L a 20% chance of developing into a tropical depression by Wednesday morning. I expect the storm will have trouble with dry air at times this week as it crosses the Atlantic, but I give 99L a 50% chance of eventually developing into Tropical Storm Ernesto sometime in the next ten days. 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 night. The long-range fate of 99L is uncertain, but a trough of low pressure is expected to be present over the Eastern U.S. early next week, which would be capable of turning 99L more to the northwest.

Hot in the Central U.S.
The heat in America's heartland continued on Sunday, with Wichita, KS hitting 111°F, just 3° short of their all-time hottest temperature of 114° set on 8/12/1936. Other notable highs on Sunday:

111° Coffeyville, KS
111° Winfield, KS
110° Chanute, KS
110° Parsons, KS
109° Joplin, MO (all-time record is 115° on July 14, 1954)

The low temperature in Tulsa, Oklahoma this Monday morning dropped to only 88°F. This is the all-time warmest low temperature in the city since record keeping began in 1905. The previous record warmest minimum temperature was 87°F set on August 2, 2011 and July 16, 1980. The high in Tulsa Monday - Wednesday is expected to reach 110° - 111°, close to the city's all-time hottest temperature of 115° set on August 10, 1936.

Jeff Masters

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Member Since: March 16, 2012 Posts: 127 Comments: 7927
Maybe is the heat of all those lights what's keeping the rain away....

Member Since: August 2, 2010 Posts: 21 Comments: 9693
Quoting JLPR2:


It's dissipating, new convection is forming south of PR.



Is that your way of saying "I want rain"? :P
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Member Since: August 2, 2010 Posts: 21 Comments: 9693
Quoting sunlinepr:


this storm reminds me of Dean
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1565. JLPR2
Quoting LostTomorrows:
99L looks to have gained in organization... slightly. What's interesting me now is the convective mass above the Lesser Antilles, it's starting to look pretty sharp, and it's kind of been persisting all day. I say that if I wake up to a new circle on the NHC page, I would not be surprised.


It's dissipating, new convection is forming south of PR.

Member Since: September 4, 2007 Posts: 7 Comments: 8499

mesoscale discussion
Member Since: March 16, 2012 Posts: 127 Comments: 7927
Member Since: August 2, 2010 Posts: 21 Comments: 9693
99L looks to have gained in organization... slightly. What's interesting me now is the convective mass above the Lesser Antilles, it's starting to look pretty sharp, and it's kind of been persisting all day. I say that if I wake up to a new circle on the NHC page, I would not be surprised.
Member Since: Posts: Comments:
1561. Bonz
Quoting wunderkidcayman:

yellow monkey B******
Japan should be red flaged
don't know why my Grand Uncle calls them yellow monkey he always said that him and his buddys was always pissed off by them back in WW2


That wasn't a bribe. Evidently, a team has to pay to file an investigation. If the investigation is accepted, as happened in this case, the money is refunded.

I assume the requirement to pay to file is to keep frivolous appeals from being filed.
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1560. JLPR2
One thing to note is the size of the circle, at least that changed.



99L is big, seems like only half the circulation has convection.
Member Since: September 4, 2007 Posts: 7 Comments: 8499
Quoting KoritheMan:
Still 20%. Can't say I agree with Richard.


he didn't sharpen the orange crayon...
Member Since: Posts: Comments:
Quoting KoritheMan:


It is, but given the convection I would have went with 30%. Nothing drastic, but a little upward push would do fine.


No reason to up the percentage really. Even if it had departed or started departing the ITCZ, they would want to see it persist for another day or so. It still has no northward movement whatsoever. To top it off, the circulation is very broad and weak. It's a nice disturbance, yes, but unimpressive on the tropical development end so far.
Member Since: July 15, 2006 Posts: 17 Comments: 10159
Quoting wunderkidcayman:
ok now I sleep 20% though it should be higher anyway I'll check back in the early morn like maybe 6 or so I'm out
Good night Wunderkid.
Member Since: March 16, 2012 Posts: 127 Comments: 7927
Quoting allancalderini:
I can`t find the one of Linda 1997 want to read the discussion when she became the strongest eastern pacific.


I've always wanted to browse through Linda's as well, for the sole reason the forecast track literally had her going into southern California.
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Quoting MississippiWx:
Ha...I got it right for once.

However, as I've said already several times, the NHC won't be impressed until it separates from the ITCZ and persists. That problem is still valid.


It is, but given the convection I would have went with 30%. Nothing drastic, but a little upward push would do fine.
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1554. JLPR2
20% seems about right, at least for the moment.

Member Since: September 4, 2007 Posts: 7 Comments: 8499
Quoting KoritheMan:
Still browsing through the archives, I found a certain advisory on Fabian (22) rather interesting:

ZCZC MIATCDAT5 ALL
TTAA00 KNHC DDHHMM
HURRICANE FABIAN DISCUSSION NUMBER 22
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT MON SEP 01 2003

THERE HAS BEEN LITTLE CHANGE IN THE SATELLITE APPEARANCE OF FABIAN
SINCE THE LAST RECON FIX AT 01/1917Z. THE INITIAL INTENSITY IS
BEING MAINTAINED AT 125 KT BASED ON DVORAK SATELLITE INTENSITY
ESTIMATES OF 127 KT FROM TAFB AND AFWA. OUTFLOW CONTINUES TO EXPAND
IN ALL QUADRANTS AND HAS ALSO BECOME QUITE SYMMETRIC.

THE INITIAL MOTION IS 285/09. THIS GENERAL MOTION HAS BEEN
MAINTAINED FOR MORE THAN 72 HOURS AND SHOULD CONTINUE FOR AT LEAST
ANOTHER 24 HOURS OR SO. OTHERWISE...THERE IS NO SIGNIFICANT CHANGE
TO THE PREVIOUS FORECAST TRACK OR REASONING. THE GLOBAL AND GFDL
MODELS HAVE DONE AN EXCELLENT JOB SO FAR WITH FABIAN...AND THE
OFFICIAL FORECAST TRACK IS JUST AN EXTENSION OF THE PREVIOUS TRACK.

SOME FLUCTUATIONS IN INTENSITY CAN BE EXPECTED DURING THE NEXT 36
HOURS OR SO...BUT OVERALL NO MAJOR INTENSITY CHANGES ARE EXPECTED
SINCE FABIAN WILL REMAIN OVER WARM SSTS OF AROUND 29C AND UNDER
WEAK SHEAR. HOWEVER...BY 72-96 HOURS...INCREASING SOUTHWESTERLY
SHEAR SHOULD INDUCE SOME FASTER WEAKENING...ESPECIALLY BY 120 HOURS
WHEN SSTS ARE EXPECTED TO DECREASE 24C.

FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS

INITIAL 02/0300Z 19.4N 58.6W 125 KT
12HR VT 02/1200Z 19.8N 60.1W 125 KT
24HR VT 03/0000Z 20.8N 62.1W 125 KT
36HR VT 03/1200Z 22.1N 63.6W 120 KT
48HR VT 04/0000Z 23.3N 64.7W 115 KT
72HR VT 05/0000Z 27.0N 67.2W 105 KT
96HR VT 06/0000Z 33.0N 68.5W 95 KT
120HR VT 07/0000Z 40.5N 67.0W 85 KT


NNNN

This has to be one of Stewart's shortest discussions.
I can`t find the one of Linda 1997 want to read the discussion when she became the strongest eastern pacific.
Member Since: Posts: Comments:
Quoting KEEPEROFTHEGATE:
iam outta here see ya around 8am or so

night everyone
Good night Keeper, hopefully you don't get any bad storms.
Member Since: March 16, 2012 Posts: 127 Comments: 7927
ok now I sleep 20% though it should be higher anyway I'll check back in the early morn like maybe 6 or so I'm out
Member Since: Posts: Comments:
1550. KEEPEROFTHEGATE (Mod)
iam outta here see ya around 8am or so

night everyone
Member Since: Posts: Comments:
Ha...I got it right for once.

However, as I've said already several times, the NHC won't be impressed until it separates from the ITCZ and persists. That problem is still valid.
Member Since: July 15, 2006 Posts: 17 Comments: 10159
Member Since: Posts: Comments:
Still 20%. Can't say I agree with Richard.
Member Since: Posts: Comments:
Still 20%

1. A WEAK AREA OF LOW PRESSURE ASSOCIATED WITH A TROPICAL WAVE LOCATED
ABOUT 1100 MILES WEST-SOUTHWEST OF THE CAPE VERDE ISLANDS CONTINUES
TO PRODUCE DISORGANIZED SHOWER AND THUNDERSTORM ACTIVITY.
ENVIRONMENTAL CONDITIONS APPEAR CONDUCIVE FOR SOME GRADUAL
DEVELOPMENT OVER THE NEXT FEW DAYS...AND THIS SYSTEM HAS A LOW
CHANCE...20 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS AS IT MOVES WESTWARD AT 10 TO 15 MPH.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
Member Since: March 16, 2012 Posts: 127 Comments: 7927
Staying with 20%. Might be 30% due to increased thunderstorm activity, but final answer is 20%. Still embedded within ITCZ. Still not its own entity.
Member Since: July 15, 2006 Posts: 17 Comments: 10159
1544. KEEPEROFTHEGATE (Mod)
ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT TUE JUL 31 2012

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

1. A WEAK AREA OF LOW PRESSURE ASSOCIATED WITH A TROPICAL WAVE LOCATED
ABOUT 1100 MILES WEST-SOUTHWEST OF THE CAPE VERDE ISLANDS CONTINUES
TO PRODUCE DISORGANIZED SHOWER AND THUNDERSTORM ACTIVITY.
ENVIRONMENTAL CONDITIONS APPEAR CONDUCIVE FOR SOME GRADUAL
DEVELOPMENT OVER THE NEXT FEW DAYS...AND THIS SYSTEM HAS A LOW
CHANCE...20 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS AS IT MOVES WESTWARD AT 10 TO 15 MPH.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER PASCH
NNNN
Member Since: Posts: Comments:
Still browsing through the archives, I found a certain advisory on Fabian (22) rather interesting:

ZCZC MIATCDAT5 ALL
TTAA00 KNHC DDHHMM
HURRICANE FABIAN DISCUSSION NUMBER 22
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT MON SEP 01 2003

THERE HAS BEEN LITTLE CHANGE IN THE SATELLITE APPEARANCE OF FABIAN
SINCE THE LAST RECON FIX AT 01/1917Z. THE INITIAL INTENSITY IS
BEING MAINTAINED AT 125 KT BASED ON DVORAK SATELLITE INTENSITY
ESTIMATES OF 127 KT FROM TAFB AND AFWA. OUTFLOW CONTINUES TO EXPAND
IN ALL QUADRANTS AND HAS ALSO BECOME QUITE SYMMETRIC.

THE INITIAL MOTION IS 285/09. THIS GENERAL MOTION HAS BEEN
MAINTAINED FOR MORE THAN 72 HOURS AND SHOULD CONTINUE FOR AT LEAST
ANOTHER 24 HOURS OR SO. OTHERWISE...THERE IS NO SIGNIFICANT CHANGE
TO THE PREVIOUS FORECAST TRACK OR REASONING. THE GLOBAL AND GFDL
MODELS HAVE DONE AN EXCELLENT JOB SO FAR WITH FABIAN...AND THE
OFFICIAL FORECAST TRACK IS JUST AN EXTENSION OF THE PREVIOUS TRACK.

SOME FLUCTUATIONS IN INTENSITY CAN BE EXPECTED DURING THE NEXT 36
HOURS OR SO...BUT OVERALL NO MAJOR INTENSITY CHANGES ARE EXPECTED
SINCE FABIAN WILL REMAIN OVER WARM SSTS OF AROUND 29C AND UNDER
WEAK SHEAR. HOWEVER...BY 72-96 HOURS...INCREASING SOUTHWESTERLY
SHEAR SHOULD INDUCE SOME FASTER WEAKENING...ESPECIALLY BY 120 HOURS
WHEN SSTS ARE EXPECTED TO DECREASE 24C.

FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS

INITIAL 02/0300Z 19.4N 58.6W 125 KT
12HR VT 02/1200Z 19.8N 60.1W 125 KT
24HR VT 03/0000Z 20.8N 62.1W 125 KT
36HR VT 03/1200Z 22.1N 63.6W 120 KT
48HR VT 04/0000Z 23.3N 64.7W 115 KT
72HR VT 05/0000Z 27.0N 67.2W 105 KT
96HR VT 06/0000Z 33.0N 68.5W 95 KT
120HR VT 07/0000Z 40.5N 67.0W 85 KT


NNNN

This has to be one of Stewart's shortest discussions.
Member Since: Posts: Comments:
Quoting KEEPEROFTHEGATE:
waitin on TWO then off to sleep for me

same here darn I wish it would come now I want to sleep
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Quoting KEEPEROFTHEGATE:
waitin on TWO then off to sleep for me
Pretty much the same for me unless storms look really threatening and are definitely coming my way.
Member Since: March 16, 2012 Posts: 127 Comments: 7927
1540. KEEPEROFTHEGATE (Mod)
waitin on TWO then off to sleep for me
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Quoting MississippiWx:


Then why did you say they look cooler? Just an observation?

cause it does on that image

Quoting ilovehurricanes13:
30% at 2am for invest 99L


I say orange 40% or 50% at 2am
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Trees and power lines being downed in W MI. I'll stay up to see if storms head my way.
Member Since: March 16, 2012 Posts: 127 Comments: 7927
Quoting wunderkidcayman:

yes I know


Then why did you say they look cooler? Just an observation?
Member Since: July 15, 2006 Posts: 17 Comments: 10159
Quoting MississippiWx:


You don't go by actual sea surface temperature readings. ENSO states are determined through anomalies, which are the highest they have been in Nino 3.4.

yes I know
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Grand Rapids severe warned
he National Weather Service in Grand Rapids has issued a * Severe Thunderstorm Warning for... Kent County in southwest Michigan... * until 200 am EDT * at 102 am EDT... National Weather Service meteorologists were tracking a line of severe thunderstorms capable of producing damaging winds in excess of 60 mph. These storms were located along a line extending from Howard City to 7 miles northwest of Sparta..and moving southeast at 40 mph. Small hail may also accompany these damaging winds. * Locations impacted include... Grand Rapids... Sparta... Cedar Springs... Rockford... Lowell... Spencer TWP... Solon TWP... Grattan TWP... Oakfield TWP... Fallassburg... Cutlerville... alpine... Comstock Park... Alaska... Alto... Grandville... Belmont... Dutton... Precautionary/preparedness actions... Severe thunderstorms can produce damaging wind in excess of 60 miles per hour... destructive hail... deadly lightning... and very heavy rain. For your protection move to an interior room on the lowest floor of your home or business. Heavy rains flood roads quickly so do not drive into areas where water covers the Road. Lat... Lon 4329 8579 4329 8531 4277 8531 4277 8578 time... Mot... loc 0504z 332deg 36kt 4336 8538 4319 8582 wind... hail 60mph <1.00in Duke
Member Since: March 16, 2012 Posts: 127 Comments: 7927
Quoting KEEPEROFTHEGATE:
nino/nina regions compare map jun july 2012



Quoting wunderkidcayman:


huh? looks...cooler than Jun


You don't go by actual sea surface temperature readings. ENSO states are determined through anomalies, which are the highest they have been in Nino 3.4.
Member Since: July 15, 2006 Posts: 17 Comments: 10159
1529. KEEPEROFTHEGATE (Mod)
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Quoting KEEPEROFTHEGATE:
heading my way later as well
They are severe with 60mph winds and they are headed for me.
Member Since: March 16, 2012 Posts: 127 Comments: 7927
1527. KEEPEROFTHEGATE (Mod)
Quoting wxchaser97:
Strong storms in MI tonight.
heading my way later as well
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1525. KEEPEROFTHEGATE (Mod)
Quoting wunderkidcayman:


huh? looks...cooler than Jun
notice that too huh
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Strong storms in MI tonight.
Member Since: March 16, 2012 Posts: 127 Comments: 7927
1523. JLPR2
Quoting wunderkidcayman:


huh? looks...cooler than Jun


This should give you a better idea.

Member Since: September 4, 2007 Posts: 7 Comments: 8499
Quoting KEEPEROFTHEGATE:
nino/nina regions compare map jun july 2012





huh? looks...cooler than Jun
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Quoting TropicalAnalystwx13:

The graveyard...scientifically called the John Hope rule...only applies to systems that have not developed. 99L should be a moderate to intense tropical storm by that time.



There is no guarantee 99L develops into a TS. The Atlantic is in the early stages of becoming favorable. I believe mid August is when the real fireworks should start and could end up being the most active month of hurricane season. September and October might be more quiet than usual.
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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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