91L near tropical depression status

By: Dr. Jeff Masters , 2:08 PM GMT on August 02, 2010

Share this Blog
2
+

A tropical wave near 12N 41W, midway between Africa and the Lesser Antilles Islands, is very close to being a tropical depression. NHC labeled this system Invest 91L yesterday, and is giving it a 90% chance of developing into a tropical depression by 8am Wednesday. Wind shear is a low 5 - 10 knots, sea surface temperatures are at record highs, and the dust and dry air of the Saharan Air Layer (SAL) are far enough to the north of 91L to potentially allow further development. The main negative for development appears to be the storm's small size, which makes it vulnerable to modest increases in wind shear or dry air entrainment. A Windsat pass from 5am EDT this morning did not show a closed circulation. Satellite imagery shows that the intensity and areal extent of 91L's heavy thunderstorms is very limited, but that a closed surface circulation may be close to forming. Low-level spiral bands and upper-level outflow are not apparent yet.


Figure 1. Morning satellite image of Invest 91L.

Forecast for 91L
There is modest model support for 91L developing into a tropical depression. Three out of six of our reliable models for forecasting tropical cyclone genesis predict 91L will develop into a tropical depression by Tuesday or Wednesday. A west-northwest motion at 10 -15 mph is predicted, which should carry 91L a few hundred miles northeast of the northernmost Lesser Antilles Islands. However, it is possible that 91L would track over the northernmost Lesser Antilles Islands, as predicted by the Canadian model. Squalls from the outer rainbands of 91L may affect islands such as Antigua and Barbuda as early as Wednesday afternoon. As 91L makes its closest approach to the Lesser Antilles on Wednesday, the storm will begin to encounter strong upper-level westerly winds associated with the counter-clockwise flow of air around an upper-level low pressure system centered between Bermuda and Puerto Rico. The latest SHIPS model forecast predicts that these winds will cause wind shear to rise to the moderate level, 10 - 20 knots, by Tuesday night, and to the high level, 20 - 30 knots, by Wednesday. There is also a great deal of dry air associated with the upper level low that may cause problems for 91L. The high wind shear and dry air should weaken and possibly destroy 91L late this week.

A trough of low pressure is expected to move off the U.S. East Coast on Friday, and this trough may be strong enough to recurve 91L far enough to the northwest that the storm will threaten Bermuda. The HWRF and ECMWF models predict 91L could pass very near to Bermuda on Saturday. It is uncertain at this time if the trough will be strong enough to recurve 91L all the way out to sea early next week, as predicted by the GFS model, or leave 91L behind to potentially move westward again into the U.S. East Coast, as predicted by the Canadian model. The amount of wind shear that might be present early next week is also highly uncertain.

Cyprus records its hottest temperature in history yesterday
The island of Cyprus recorded its hottest temperature in its history on August 1, 2010 when the mercury hit 46.6°C (115.9°F) at Lefconica. The old record for Cyprus was 44.4°C (111.9°F) at Lefkosia in August 1956. An older record of 46.6°C from July 1888 was reported from Nicosia, but is of questionable reliability.

The year 2010 is now tied with 2007 as the year with the most national extreme heat records--fifteen. There has been one country that has recorded its coldest temperature on record in 2010; see my post last week for a list of the 2010 records. My source for extreme weather records is the excellent book Extreme Weather by Chris Burt. His new updates (not yet published) remove a number of old disputed records. Keep in mind that the matter of determining extreme records is very difficult, and it is often a judgment call as to whether an old record is reliable or not. For example, one of 2007's fifteen extreme hottest temperature records is for the U.S.--the 129°F recorded at Death Valley that year. Most weather record books list 1913 as the year the hottest temperature in the U.S. occurred, when Greenland Ranch in Death Valley hit 134°F. However, as explained in a recent Weatherwise article, that record is questionable, since it occurred during a sandstorm when hot sand may have wedged against the thermometer, artificially inflating the temperature. Mr. Burt's list of 225 countries with extreme heat records includes islands that are not independent countries, such as Puerto Rico and Greenland. Seventy four extreme hottest temperature records have been set in the past ten years (33% of all countries.) For comparison, 14 countries set extreme coldest temperature records over the past ten years (6% of all countries). I thank Mr. Burt and weather record researchers Maximiliano Herrera and Howard Rainford for their assistance identifying this year's new extreme temperature records.

Next update
I'll have an update later today if 91L develops into a TD.

Jeff Masters

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 509 - 459

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22Blog Index

Quoting Hurricanes101:


but to say that now when it just formed and is still 1350 miles from any landmass is even more nuts
At least half on here will Poof you, Ignore you, yell about your comment, call you a Troll, call you a Downcaster, but whatever, as long as you are making educated guesses or following the most reliable tools we have, which are not perfect, then you have the right to post comments. The real loosers here, are those that state ridiculous predictions that use no common sense and defy logic. Those people should go poof themselves, afind a psychic site to visit.
Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
I'll be updating it in the evening

your blog header should say

"FISH TALES OF THE ATLANTIC"

that sounds about right for now
Member Since: July 15, 2006 Posts: 171 Comments: 53827
Quoting FloridaHeat:
is a fish storm just a storm that stays over water???


Yup.
Member Since: Posts: Comments:
is a fish storm just a storm that stays over water???
Member Since: Posts: Comments:
Quoting StadiumEffect:
Large outflow boundaries moving towards the north/ northwest can be seen on the visible loop, but convection is increasing else where. The mass is should already be far enough behind the depression that development wouldn't be hindered too much. Currently there is nothing at the 850mb level and the heavy thunderstorms will need to persist to get anything going.


It should get going more and more as it approaches the 30+Celsius (SST) to the west. In addition, there is another additional batch of 30+Celsius water another 300 miles west of the first batch.
Member Since: September 30, 2005 Posts: 0 Comments: 1606
503. Prgal
Wow, I leave for a few hours and when I come back the blog is full of fishcasters! I miss the days when you could actually learn from the things posted here. We still have those kind of posts...but...sigh...not all the time.
Member Since: Posts: Comments:
Quoting Drakoen:
One hour and a half after TD4 is official and bloggers are ripping the storm that they declared TD 4 hours before the NHC lol. Much more entertaining to not post and sit back and watch.


rofllmao, Drak. Thought I'd pop in and see the latest, but...

Guess I'll take a look now and then at radar and wait for StormW's update tonight or tomorrow morning.

Relatively cool and drizzly here - what a welcome relief from the massive heat indices of July. I think we have another day or so before the high builds back in and we join the rest of the South in suffering with heat and humidity. (my weather so I stay on topic, LOL)
Member Since: Posts: Comments:
Quoting stevenshsjay1:
TD 4 will develop into TS Colin but no more. The wave east of Colin is the one to watch.

Depends on how much TD4/"future Colin" influences it. It could hinder development since they are fairly close
Member Since: Posts: Comments:
Quoting stevenshsjay1:
TD 4 will develop into TS Colin but no more. The wave east of Colin is the one to watch.

Yeah. I said that the wave to the east of 92L is the one I am betting on, since it was on the African coast.
Looks very potent to me, and has done for a while.
92L is an enigma though....... it could do a number of different things in the next 3-4 days.
Member Since: October 24, 2005 Posts: 0 Comments: 24307
Quoting WeatherMSK:


It's not a waste of time when you look at the pattern that invests and storms have taken this year. I think it's crazy to call this a fish storm so early. There's alot of time to see what will happen.


You don't think that all these sophisticated models take these things into consideration!? - I mean come-on!! Every storm will behave given the pattern it will see NOW and NOT how other storms behaved last week, month, year etc!
However, i am of course not stopping anyone voicing their opinion, it's just that this blog would be better served if bloggers are a little more learned about tropical weather!!
Member Since: Posts: Comments:
Quoting NASA101:
What I have learned in the past few years that when you have 80% of models, both statistical and dynamical agreeing on a similar track then 99% of the time it's Game, Set & Match!!

So, the bloggers who cites "their gut-feeling", "wishcasting", "moving West syndrome" is just a waste of time!

Potential Colin will most likely be out to the sea as a tropical storm - models say this and so does the NHC!



And you do realize models can change in 24 hours and so can the NHC track, if that was the case as you say Ike should of hit South Florida and not Tx. Today's outlook on TD4 is bleak and the track yes can take it out to sea away from land lets hope it does, but things can and do change and the conditions could improve for TD4 or worsen. This has alot of real estate to go lets be realistic that conditions can change and not limit ourselves to one NHC official track and one day of model runs.
Member Since: Posts: Comments:
493. Skyepony (Mod)
TD04 on RGB loop.
Looking better than it did before.
Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
I'll be updating it in the evening.


looking forward to it :)
Member Since: July 3, 2010 Posts: 0 Comments: 427
Quoting Dropsonde:
I know, this has really gotten ridiculous. I don't mind the RIP posts as much as I mind the posters who jeer at or attempt to shame people who do like watching development and want it to happen because it is amazing and beautiful. This is a blog by a meteorologist, which is frequented by meteorologists, meteorologists-in-training, and people who like watching interesting weather for its own sake, not because it is "cool" to see houses destroyed. Anyone who cannot understand that extreme weather is fascinating for its own sake and thinks that anyone who enjoys it just wants to see human dwellings get destroyed needs to find another blog, IMO! Nature will do what the laws of physics dictate it must do, and if human settlements are in the way, that's unfortunate, but it doesn't make the weather phenomena any less amazing and it certainly does not make them evil or horrible. I truly believe that attacking people for enjoying the development of a system is nothing more than trolling, and there is way too much tolerance for it. It is severely decreasing the fun of the blog.
Great Point! I much more enjoy watching storms that only affect maritime interest (at least those interest can adjust their heading).
Member Since: September 1, 2007 Posts: 0 Comments: 1316
It's not wishcasting, nobody in their right minds wants to be struck by a Hurricane. What Im saying is it's a fact that the initial track you see from the time a system develops into a Depression are 80-90% different until 5-6 days out. Adjustments on the tracks are always made throughout that time period. In other words the track in 144hrs from now will be different from what the track is today. And as TD 4 continues a W-WNW track you will see the track start to bend to the left through time.
Member Since: Posts: Comments:
Quoting smuldy:
It WONT track westward it WILL die or go out to sea sad to say


"Sad to Say"??????

If it tracks to LAND then it's "Sad to Say!"
Member Since: Posts: Comments:
34West just increased areal coverage and intensity in the last 30 minutes. They need to place a floater on it also since it is in a better environment than TD4.
Member Since: September 30, 2005 Posts: 0 Comments: 1606
To be honest, I see alot more wishcasting on the fish side of things than I do people saying its going west to land. Most that say it's going west are not completely downplaying a potential recurvature. There's alot of time left. No need to rush forecasts right now.
Member Since: Posts: Comments:
Quoting sarahjola:
mh09- will you be updating your blog soon. i like your blog and would like to see your side of things. i'm off, but i will check back later and give your blog a look before coming here. have a good day everyone:)
I'll be updating it in the evening.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting cirrocumulus:
34West needs to stop diving south into the ITCZ. It is putting distance between TD4 and itself however.
Large outflow boundaries moving towards the north/ northwest can be seen on the visible loop, but convection is increasing else where. The mass is should already be far enough behind the depression that development wouldn't be hindered too much. Currently there is nothing at the 850mb level and the heavy thunderstorms will need to persist to get anything going.
Member Since: Posts: Comments:
One thing I have noticed is the relative lack of support from the GFS ensemble members. Only about 1/3 hold a long term track.


Member Since: Posts: Comments:
Quoting StormChaser81:


Don't ya think it could change if upper level conditions change, its still a ways out there. I guess I'm out in left field. I hope your right.
Quoting pcola57:

Hey Tampa...I usually listen to what you got to say but your off the wall today!!! NOBODY knows where this one is going...on topic now...Pensacol Naval Air Station
95°F
Feels Like: 108°
Wind Chill: 95° Ceiling: Unl
Heat Index: 108° Visibility: 10mi
Dew Point: 76° Wind: 6mph
Humidity: 54% Direction: 290° (WNW)
Pressure: 29.97" Gusts: NA
Report Text: KPNS 021553Z 29005KT 10SM CLR 35/24 A2998 RMK AO2 SLP152 T03500244
Quoting TampaSpin:
ANYONE AND I DO MEAN ANYONE, that does not Currently have this as a Storm for the fishes is truly out in left field with nobody else to throw too....a lot of non-sense being posted now.


Read what i said.......i said CURRENTLY.....24hrs things could change, but as of now nearly every model has this as a fish storm CURRENTLY ...the word currently is the key word....



Member Since: September 2, 2007 Posts: 178 Comments: 20439
mh09- will you be updating your blog soon. i like your blog and would like to see your side of things. i'm off, but i will check back later and give your blog a look before coming here. have a good day everyone:)
Member Since: Posts: Comments:
Reply #451- Great article MH09. Right on the money!
Member Since: Posts: Comments:
Quoting stevenshsjay1:

The problem is, calling it "34W" makes it sound like it's a Chinese invest or something...might as well call it "the African wave" or "pre-92L"
There isn't even a tropical wave there and 850mb vorticity is nearly non-existent.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Levi posted a stat yesterday that 1/2 of all August storms were fishes; that is actually a good thing if it comes to pass.
Member Since: August 8, 2006 Posts: 0 Comments: 9134
Quoting pcola57:

I think you mean the heat index...and yes thats hot...i'm in myrtle grove and the heat index from Naval Air Station 15 minutes ago was 111 degrees...went for a swim in the pool and pool temp was 92 degrees...not much relief
OC I meant the HIndex. Sitting at 95t/84dp at the moment, which puts our heat index at 124. Storms brewing about 20 miles east. Our pool water is currently 96'. BLECH.
Member Since: Posts: Comments:
474. unf97
I would think that after all of these years of studying the weather and the tropics that people should definitely understand that patterns and conditions in the atmosphere can change daily. This applies in all facets of studying the weather.

I will never understand some people on this blog who simply don't apply this fact into their thinking and presume go on into their wishcasting mode. But, this is just how things are with some folks on Dr. Masters' blog.
Member Since: Posts: Comments:
Quoting NASA101:
What I have learned in the past few years that when you have 80% of models, both statistical and dynamical agreeing on a similar track then 99% of the time it's Game, Set & Match!!

So, the bloggers who cites "their gut-feeling", "wishcasting", "moving West syndrome" is just a waste of time!

Potential Colin will most likely be out to the sea as a tropical storm - models say this and so does the NHC!



BINGO
Member Since: July 25, 2008 Posts: 0 Comments: 596
Quoting NASA101:
What I have learned in the past few years that when you have 80% of models, both statistical and dynamical agreeing on a similar track then 99% of the time it's Game, Set & Match!!

So, the bloggers who cites "their gut-feeling", "wishcasting", "moving West syndrome" is just a waste of time!

Potential Colin will most likely be out to the sea as a tropical storm - models say this and so does the NHC!



It's not a waste of time when you look at the pattern that invests and storms have taken this year. I think it's crazy to call this a fish storm so early. There's alot of time to see what will happen.
Member Since: Posts: Comments:
What I have learned in the past few years that when you have 80% of models, both statistical and dynamical agreeing on a similar track then 99% of the time it's Game, Set & Match!!

So, the bloggers who cites "their gut-feeling", "wishcasting", "moving West syndrome" is just a waste of time!

Potential Colin will most likely be out to the sea as a tropical storm - models say this and so does the NHC!

Member Since: Posts: Comments:
469. Bonz
Sure looks like another storm trying to form behind it.
Member Since: Posts: Comments:
Quoting reedzone:


I never mentioned anything about it becoming a Hurricane. I know there are factors inhibiting strengthening. I'm talking about the track, it's too early to tell if this recurves or not.


I meant it to mean that it has plenty of obstacles to overcome and it is a small compact system. We'll have to wait and see.
Member Since: Posts: Comments:
Quoting oracle28:


Personally, I think the hyping of "storms" like Bonnie, numb people to the real threats of major hurricanes. People were saying it's (91L) already a tropical storm, which is nuts.

1) It's not expected to reach hurricane strength.
2) The closest landmass in the 'expected' path is Bermuda.

If a recurving TS fascinates you, enjoy it. But don't get angry for being reminded it's a fish TS.
I didn't say one word about fish storms. That is a matter of track, not development of the system itself. There are quite a few people who think that anyone who wants to see a storm develop are somehow "bad" people, and that by RIPing systems they are the "good" people. But it is interesting that you thought of fish spinners! That shows that it really is all about the human impact, not the meteorology, and this is a meteorology blog, NOT a disaster relief or humanitarian blog!
Member Since: Posts: Comments:
Quoting kuppenskup:
Honestly as TD 4 continues it's Westward motion over the next few days I think your gonna see that forecast track move to the left over a period of time. The original track that first comes out by the NHC is very seldom correct, they always have to adjust it in some way.


I would agree with ya on that one. Thats where I stand with this whole situation. Recurvature is not set in stone.
Member Since: Posts: Comments:
34West needs to stop diving south into the ITCZ. It is putting distance between TD4 and itself however.
Member Since: September 30, 2005 Posts: 0 Comments: 1606
Quoting sammywammybamy:


Notice little to no steering north of the islands, the interaction between the high and trough should slow the progress of TD4, it's not a guarantee it recurves, sorry, just looking at the big picture.
Member Since: July 1, 2008 Posts: 13 Comments: 7387
Quoting Drakoen:
One hour and a half after TD4 is official and bloggers are ripping the storm that they declared TD 4 hours before the NHC lol. Much more entertaining to not post and sit back and watch.


some were ripping it before it was even a TD.
Member Since: Posts: Comments:
Quoting Hurricanes101:


but to say that now when it just formed and is still 1350 miles from any landmass is even more nuts


Just to be clear, I'm saying calling TD4 a TS this morning is the "nuts" part, not the path.
Member Since: July 25, 2008 Posts: 0 Comments: 596
Honestly as TD 4 continues it's Westward motion over the next few days I think your gonna see that forecast track move to the left over a period of time. The original track that first comes out by the NHC is very seldom correct, they always have to adjust it in some way.
Member Since: Posts: Comments:
Quoting Hurricanes12:


It's already receiving dry air and it's going to be sheared quite a bit in a day or two.


I never mentioned anything about it becoming a Hurricane. I know there are factors inhibiting strengthening. I'm talking about the track, it's too early to tell if this recurves or not.
Member Since: July 1, 2008 Posts: 13 Comments: 7387

Viewing: 509 - 459

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Scattered Clouds
67 °F
Scattered Clouds