TD 8 forms; 97L a potential threat to the Caribbean and U.S.

By: Dr. Jeff Masters , 3:30 PM GMT on August 19, 2011

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Tropical Depression Eight formed last night near the coast of Honduras, and is headed westwards towards a landfall in Belize on Saturday. TD 8 is a small storm, so will impact a relatively small area of northern Honduras, northern Guatemala, all of Belize, and southern portions of Mexico's Yucatan Peninsula. TD 8 has just enough room between its center and the coast of Honduras to intensify into a moderate strength tropical storm with 50 - 60 mph winds before landfall. It is very unlikely TD8 has the time or room to intensify into a hurricane; NHC gave the storm just a 7% chance of making it to hurricane strength in their 11am EDT wind probability forecast. Should TD8 make it to tropical storm strength, it would be called Harvey.


Figure 1. Morning satellite image of TD 8.

Invest 97L likely to become a tropical storm next week, could threaten the U.S.
A tropical wave near 14°N 48°W, about 800 miles east of the Lesser Antilles Islands, is moving westward near 20 mph. This wave, designated Invest 97L by NHC yesterday, has seen a marked increase in its heavy thunderstorm activity this morning, but dry air to the north and west is slowing development. An impressive amount of large-scale spin is obvious in visible satellite loops, but the storm is at least a day away from forming a well-defined surface circulation. Ocean temperatures are about 28.5°C, about 2°C above the threshold needed to support a tropical storm, and wind shear is low, 5 - 10 knots.


Figure 2. Morning satellite image of the tropical wave 97L.

The computer models have shown an unusual amount of agreement in developing 97L over the past few days, and all the ingredients seem to be in place for a tropical storm to form by Monday or Tuesday as 97L crosses the Northeast Caribbean. The atmosphere is expected to be moister over the Caribbean, wind shear will remain a low 5 - 10 knots, and sea surface temperatures will increase to near 29°C. The main impediment for development will likely be two-fold: too much dry, stable air, and proximity to land.

As seen in Figure 3, there has been an unusual amount of dry, stable air in the Atlantic this year, due to a combination of dry air from Africa, and upper-atmosphere dynamics creating large areas of sinking air that dry as they warm and approach the surface. This stable air has been largely responsible for the fact that none of our seven tropical storms so far this year has made it to hurricane strength, despite the presence of sea surface temperatures that are the 3rd warmest on record across the tropical Atlantic. Tropical Storm Emily in early August encountered problems with dry air when it crossed the Northeast Caribbean, and 97L may have similar difficulties.


Figure 3. Vertical instability of the atmosphere during 2011 in the Caribbean (left) and tropical Atlantic between the Lesser Antilles Islands and coast of Africa (right.) 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. Observed vertical instability (blue line) has been much lower than the climatological average from previous years (black line), due to an unusual amount of dry air in the atmosphere, inhibiting tropical storm development this year. Image credit: NOAA/CIRA.

Encounters with land will be another potential major problem for 97L. Most of the computer models take 97L near or over Puerto Rico Sunday night, then very close to or over mountainous Hispaniola Monday night through Tuesday. It is unlikely that 97L will be stronger than a 55 mph tropical storm when it encounters these islands, and passage over the islands could severely disrupt the storm. However, if 97L takes a path just south or north of Hispaniola, the potential exists for the storm to intensify into a hurricane.

There will be moderate wind shear of 10 - 20 knots to the north of the islands early next week, so a path just to the south of the Dominican Republic and Haiti would be more likely to let 97L intensify into a hurricane. A west-northwest motion is likely for 97L through Wednesday, which would bring the storm to the vicinity of Jamaica-Central Cuba-the Central Bahamas on Wednesday. On Wednesday and Thursday, the models agree that a trough of low pressure will dip down over the Eastern U.S., which is likely to turn 97L to the north. The exact timing and strength of this trough varies considerably from model to model, and will be critical in determining where and when 97L will turn to the north. The best model for predicting the timing and strength of such troughs over the past two years has been the ECMWF (European Center model), and this model currently brings 97L into the Florida Keys on Thursday night next week. You can view ECMWF forecasts on our wundermap with the model layer turned on. The European Center does not permit public display of tropical storm positions from their hurricane tracking module of their model, so we are unable to put ECMWF forecasts on our computer model forecast page that plots positions from the other major models.

Remember that a 7-day forecast by even our best model will be off by an average of over 700 miles, so it is too early to tell what part of the U.S. might be most at risk from a strike by 97L. This weekend would be a good time to go over your hurricane preparedness.


Figure 4. Morning satellite image of Invest 98L off the coast of Africa.

Invest 98L near the coast of Africa
A tropical wave near the coast of Africa, a few hundred miles southeast of the Cape Verde Islands, is moving west to west-northwestward at 10 - 15 mph. This wave, designated Invest 98L by NHC yesterday, is large and well-organized, with a modest amount of spin and heavy thunderstorm activity. 98L will bring strong, gusty winds and heavy rains to the Cape Verde Islands today and Saturday as the storm skirts to the south. So far this morning, top sustained winds measured in the islands were 24 mph at Mindelo. Water temperatures are warm, near 27 - 28°C, and wind shear is low, 5 - 10 knots, so 98L should continue to organize today. NHC gave the storm a 50% chance of developing into a tropical depression in their 8am advisory. Once 98L passes to the west of the Cape Verde Islands, it has a long stretch of ocean to cross before it could affect any other land areas. Approximately 70 - 80% of all tropical cyclones that pass this close to the Cape Verde Islands end up curving out to sea and not affecting any other land areas, according to Dr. Bob Hart's excellent historical probability of landfall charts. The latest set of long-range model runs go along with this idea, but it is too early to be confident of this.

Jeff Masters

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Quoting shadoclown45:
Taz Im sorry i have been mean to you in the past i didnt realize how much of a jerk i have been if you could forgive me i would like to forcast weather with you and the rest of this blog. Im sorry taz i have my own faults too.



thats ok whats talk weather
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2641. KEEPEROFTHEGATE (Mod)
T.C.F.W.
08L/TS/H/CX
NEARING LANDFALL



Direct Hit:
A close approach of a tropical cyclone to a particular location. For locations on the left-hand side of a tropical cyclone's track (looking in the direction of motion), a direct hit occurs when the cyclone passes to within a distance equal to the cyclone's radius of maximum wind. For locations on the right-hand side of the track, a direct hit occurs when the cyclone passes to within a distance equal to twice the radius of maximum wind. Compare indirect hit, strike.

Strike:
For any particular location, a hurricane strike occurs if that location passes within the hurricane's strike circle, a circle of 125 n mi diameter, centered 12.5 n mi to the right of the hurricane center (looking in the direction of motion). This circle is meant to depict the typical extent of hurricane force winds, which are approximately 75 n mi to the right of the center and 50 n mi to the left.

2011 Atlantic Storm Name List
Irene Jose Katia Lee Maria Nate Ophelia Philippe Rina Sean Tammy Vince Whitney



Member Since: July 15, 2006 Posts: 165 Comments: 52383
2640. Levi32
Fresh ASCAT of 97L shows nada underneath the mid-level center, which as mentioned before is obvious on satellite imagery.

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2639. Ryuujin
Quoting Tazmanian:



POOF all so larn how too spell


The EPICNESS of this quote can not be understated.

Just... Awesome Taz... Just... I'm in awe bro.


:D
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Quoting Tazmanian:
97L can i fart for you


LMAO! Wat does that mean, Taz?
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Vanishing... for the moment...

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Could be quite active in our basin (If it verifies).

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00z nam 54 hours out
Member Since: July 31, 2011 Posts: 4 Comments: 753
Quoting weatherh98:
one thing i love about weather it always changes, it is slow but obvious


Not sure about that.. it has not changed a bit here in Texas for weeks... over 100 everday for the past few weeks and no rain for months.
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Taz Im sorry i have been mean to you in the past i didnt realize how much of a jerk i have been if you could forgive me i would like to forcast weather with you and the rest of this blog. Im sorry taz i have my own faults too.
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Riddle me this,riddle me that,where will all the hurricanes scat.
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Quoting Tazmanian:
97L can i fart for you


How about for Emily?
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I'm just going to say this - I would buy gas now before we get a possible price run up. When this thing gets declared a TD/TS - this particular oil reporting service called OPIS will quote Jeff's posts. Traders on the Nymex will know something can make it into the GOMex. Prices will jump.
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2628. pottery
Quoting Tazmanian:
97L is now haveing a big blow up in the last few update loop



Getting to DMax in 6 hrs or so.
Should be fun....
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Quoting tcbob8794:
Any chance of TD 9 at 11 PM?
No, but thanks for asking....sigh
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Quoting K8eCane:


well i should clarify that. There have been storms that have hit the NE gulf and come over into NC but not likely at this point. Stay tuned though


Because I keep seeing a lot of rain being spitted out from this remnant future hurricane Irene.
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Quoting tcbob8794:
Any chance of TD 9 at 11 PM?
No. Not organized enough.
Member Since: October 9, 2008 Posts: 0 Comments: 8242
Interesting discussion
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2623. Skyepony (Mod)
Fresh ASCAT of 99L. Much less impress than the WINDSAT a few hours earlier.
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2622. Levi32
Quoting KEEPEROFTHEGATE:
we shall see don't go blind


The quest that is meteorology is finding ways to navigate through the darkness to reach the end-destination.
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2620. Grothar
Quoting Tazmanian:
97L is now haveing a big blow up in the last few update loop




Noticed that in the last few frames. I was just posting the animation of it. Looks like it could get a little stonger by tomorrow or Sunday. You can see it quite well in the animation


Link
Member Since: July 17, 2009 Posts: 64 Comments: 23749
A few days ago SOMEONE on here posted a link to comments from those researching the "pouches". I think it was in reference to P18L (what I think became 98L). The continued reference to the "beast to the east" was goosebump stuff. I'd love to read their most recent comments. So if you posted that link, or smartly bookmarked that link.. I would be cool to share again.

Not that we don't have enough to watch at the moment. (yeah I'm in Florida (west coast)). But still like to be clued in on what else is coming down the pike.
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one thing i love about weather it always changes, it is slow but obvious
Member Since: June 17, 2011 Posts: 11 Comments: 6439
Quoting Tazmanian:




how about now

LOLOL
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Quoting tropicfreak:


Can't remember, though I have fished down in south central VA, in Nottoway County, Ft Pickett.
Mountain Streams are hurting because the aquifers and the biomass didn't get it's winter replentishment and the late spring rains meant that the trees sucked the water table down. We are not showing up on the drought charts but we are still at a stress level here. Nothing like the Texas situation but a couple of weeks without rain and we could be in trouble, especially as fall approaches with the leaf fall the forest could turn to tinder PDQ.
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I thought the steering would change with Harvey is the pressure dropped below 1000 MB. Is this not correct, and if not at what pressure does the steering change at? TIA
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Quoting muddertracker:

LOL! Sure...why not?



sweet
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2611. KEEPEROFTHEGATE (Mod)
Quoting Levi32:


I think they got a little too excited over the mid-level circulation, when the surface winds flowing underneath of it have been all out of the northeast. They are also very confident due to the model support, but they might be pushing the 48-hour window a little bit. We'll see.
we shall see don't go blind
Member Since: July 15, 2006 Posts: 165 Comments: 52383
Quoting bigeasystormcaster:


THAT WAS NOT YESTERDAY'S. IT IS THE MOSTRECENT BECAUSE THIS MODEL HAS NEVER HAD IT GOING THIS FAR WEST UNTIL THIS MOST RECENT RUN I OBSERVED!

Check out this link!!! This IS the latest GFS at 18Z on 8/19/2011!!!
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2608. nigel20

99L
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97L is now haveing a big blow up in the last few update loop


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Quoting xtremeweathertracker:

My friend that is yesterday's 18Z i believe i just checked today's 18z which targets the NE Gulf Coast near Florida!!!Link


HOPE YOU'RE RIGHT!!!
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Quoting Tazmanian:




how about now

LOL! Sure...why not?
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Quoting tcbob8794:
Any chance of TD 9 at 11 PM?




sorry but ahahahahahahhahahhahaha its mid level but in all seriousness it will take a day at least
Member Since: June 17, 2011 Posts: 11 Comments: 6439
2603. K8eCane
Quoting WeafhermanNimmy:


Even weakening strong tropical storm?


well i should clarify that. There have been storms that have hit the NE gulf and come over into NC but not likely at this point. Stay tuned though
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2602. Thrawst
Quoting tcbob8794:
Any chance of TD 9 at 11 PM?


No surface circulation in 97L, centers of 98L and 99L are may merge fairly soon, with 98L having little change in organization since earlier today. I believe no. Correct me if i'm wrong, NHC :D
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Quoting tcbob8794:
Any chance of TD 9 at 11 PM?


No, thats too early
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2600. gugi182
i got 2 question can someone answer me I'm just curious

1. What is a troll, i see everybody writing Trolls?
2. What is DMAX?
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Quoting tcbob8794:
Any chance of TD 9 at 11 PM?



nop not tonight
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Quoting tcbob8794:
Any chance of TD 9 at 11 PM?


No.
Member Since: July 6, 2010 Posts: 109 Comments: 30291
2597. nigel20
Quoting TropicalAnalystwx13:

WOW!
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Quoting TropicalAnalystwx13:


WOAH!! Firing some really cold cloud tops.
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Quoting BiloxiGirl:
Back in the 70's and 80's when I was a kid, they didn't even mention storms for our area until they started to enter the GOM. These days I am not sure it does any more good to talk about them, bc none of us will get serious about preparation until like 48 hrs out. I mean we'll do basic stuff, but not board up windows or make hotel reservations to evacuate. Kind of a bunch of hype if you stop and think about it. Glad for the technology but it is more entertainment than effective for real preparation. These storms go where they want.


Wrongo!!! I make reservations at least a week out as I have animals to travel with, plus it takes me several days to prep my house. I watch every minute VERY carefully!
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As a precaution if you live in Florida - DO NOT buy a lot of perishable groceries beyond this weekend. Try to cook some of the food you have in the freezer this week in case a hurricane does affect your area.
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Quoting TropicalAnalystwx13:


big clouds
Member Since: June 17, 2011 Posts: 11 Comments: 6439
2592. Thrawst
Quoting TropicalAnalystwx13:


That's some solid convection right there... if it sustains itself and continues to organize further, RI is indeed a possibility given it's small nature.
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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.