TD 8 forms; 97L a potential threat to the Caribbean and U.S.
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
Reader Comments
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Yep
And I follow Picasso.
If it is, a lot of people in here wasted their money on art school.
Watch the GFS loop and note the L for the wave after 98L. GS puts it in park and leaves it right by the Canary Islands, immobile for days on end...
Approaching the Canary Islands at 108 hours:
108 hours later, it has successfully traveled across the Canary Islands and parked:
Sure there is DON'T LOOK ETHEL!!!!
Good morning.
Blog update:
Tropical Tidbit for Friday, August 19th, with Video
Thank you so much for the great update Levi. As I was pointing out yesterday it is still too early to pinpoint a landfall location especially due to the fact that this system is still in it's embrionic stages sort of speak. I concur with your analysis of how timing will affect this system. I believe that if it reaches TS status or stronger south of Puerto Rico it will cross north anywhere in the area between Hispaniola and Puerto Rico itself and become a FL coast rider and perhaps make landfall somewhere in the East Coast. As far as it recurving completely out to sea as we have previously seem, the stage will just not be set up for that to happen. Now if it stays as a wave or TD it will tend to continue a more westward movement and become a potential Central Gulf Coast to eastern Gulf Coast threat. Now this bring me to my questions. 1 Will this steering pattern become the norm for the peak of this season? and 2 What posibilities you see of this systems to form if it happen to enter the Caribean dead zone?
Indeed. With three active objects, it would be immensely helpful if posters would refer to any of the systems with a word other than the non-specific "it".
TD.8_12amGMT_ATCF : Starting 18August_12amGMT and ending 19August_12amGMT
The 4 short line-segments represent TD.8's path and
the longest line-segment is the straightline projection.
Using straightline projection of the travel-speed&heading derived from the ATCF coordinates spanning the 6hours between 6amGMT then 12amGMT :
TropicalDepression8's travel-speed was 7.2mph(11.53k/h) on a heading of 323.3degrees(NW)
TD.8 was headed toward passage over Cozumel,QuintanaRoo ~2days&1hour from now
(though I wouldn't count on TD.8 continuing to move that slowly)
Copy&paste neg, 15.3n79.4w-15.4n80.4w, 15.4n80.4w-15.4n81.5w, 15.4n81.5w-15.5n82.9w, 15.5n82.9w-16.0n83.3w, czm, 15.5n82.9w-20.345n86.9w into the GreatCircleMapper for more info
The previous mapping (for 19August_6amGMT)
These aren't forecasts, they are solutions to a very complex problem in one of the ultimate non-linear dynamical systems. They show things that might come to pass.
The fact that multiple different models are coming to essentially the same conclusion (that conclusion being that the pathway opens for a tropical cyclone to form and hit the US) indicates that such a scenario is significantly more likely than is normal. The particulars of any given run, while interesting and in some ways entertaining, are not so important.
No solution for, for instance, Emily or 93L, ever had this level of consistency (see interesting and entertaining above).
Tomorrow
I. ATLANTIC REQUIREMENTS
1. SUSPECT AREA (APPROACHING LESSER ANTILLES)
FLIGHT ONE -- TEAL 71
A. 20/1800Z
B. AFXXX 01GGA INVEST
C. 20/1615Z
D. 15.3N 57.5W
E. 20/1730Z TO 20/2130Z
F. SFC TO 10,000 FT
Eeek! Was that one long run-on sentence?
Better get your shield ready Ike
Using It is fine.
Providing that the other two systems are called Fester and Lurch...
Be ready for a weather emergency in advance and put together a basic survival kit.
Food Items:
Bottled drinking water
Bread
Crackers
Cookies, snacks
Canned fruit
Canned meat, fish
Apples, bananas
Dried fruit
Canned/boxed beverages
Fruit drinks
Peanut butter
Non-Food Items:
Ice
Coolers
Plastic forks and cups
Napkins
Can opener (non-electric)
Batteries for flashlights and radio
Plastic trash bags
Charcoal
Water purifying tablets
Flashlights
Candles and matches
Clothing and bedding
Extra socks and underwear
Pillows
Sleeping bag and blankets
Washcloth and towel for each person
Soap, toothbrushes, toothpaste
Deodorant
Shaving kit
Contact lens solution
Hair care items and mirror
Dentures
Sanitary napkins and tampons
Paper towels, toilet paper
Hearing aid batteries
Watch or clock
Portable radio with fresh batteries
Chlorine tablets
Spare pair of eyeglasses
Cash
Prescription medicines
Important papers (drivers licenses, insurance policies, social security cards)
Toolbox with hammer, nails, screws, screwdrivers and wrenches (to use after the storm to make your home livable again)
Cell phone (take an extra battery or a means to power or charge it)
list of people to contact for emergencies
First Aid Kit:
Keep contents of first aid kit in a waterproof metal or plastic box.
Prescription medicines (four-week supply)
Bandages and Band-Aids
Antiseptic
Adhesive tape rolls
Aspirin
Insect repellent
First aid handbook
Scissors
Antibacterial soap
Safety pins
Thermometer
Needle (for splinters)
Items for Infants:
Small toys include favorite stuffed animals
Clothes
Diapers and baby wipes
Milk or formula
Powders, creams or ointments
Bottles and nipples
Baby food
Sheets, blankets, rubber pads
Portable crib
Plastic bags
Pacifiers
Andy Whorhol Grammar art?
ECMWF is up the East Coast, GFS up the West Coast. 200 mile difference that far out is pretty darn close to me. Early tracks, the ones that matter most, are relatively similar.
we have as good a shot as anywhere else...or not....
Tha High pressure ridge will serve as a barrier protecting West of the Mississippi River. What this means is that depending on the steering patterns and how they pan out you could make a cone that would have East of the Mississippi Delta as the outliers and the area in the eastern Gulf coast between Tallahasee and Tampa FL as the middle of the cone. This is in no way official due to the fact that this system have not even formed and I would absolutely not rule an East Coast rider with a potential landfall somewhere on the East Coast. As a Matter of fact that seems to be the preffered scenario right now and the models if not by now should start pointing that out soon.
The models pretty much mean nothing at this time.. imo
lol
For an exact landfall location and intensity, yes, for a pattern that is being shown consistently and by multiple models, not so much.
The 00z ECMWF was showing a Gulf threat in yesterday%u2019s 12z cycle, but the 00z is further east again showing a landfall in southeast Florida and then a close pass off the southeast coast and what looks to be a turn to the north at the very end as a trough dives in from the Midwest that would threaten the mid-Atlantic coast possibly after day 10. The 00z GGEM shows a similar track to the 00z ECMWF. The 6z GFS showed a track into the eastern Gulf and then the trough capturing it and turning it NE into the FL panhandle and across the southeast US and the 12z GFS shows a similar track with landfall in Pensacola.
All and all not a lot has changed since yesterday. I still expect this to develop later than sooner and probably threaten the US. Florida seems to stand the highest chance of a hit, but I am not so confident on west vs. east coast of Florida. Stay tuned over the weekend. My feeling is that I have a hard time seeing this going any further west than Mobile Bay with the progged upper air pattern.
ty
And here is the second element, not so unanticipated. When we were talking about the strength and location of the AB high back in July, we were thinking about the impact on forward speed. It does add to an interesting equation...
Where r u located, Tpig?
Hey P451, I gave this a plus, because it gives a good explanation of how long-range models should and should not be used in language most of us can understand [i.e. no excuses about it not being clear]. I also think that graphic is the best I've seen in a while.... can't remember who it was a few years back that had the "stupid" circle, which illustrated that the basin is wide open for business. But this does an excellent job of showing what to expect track-wise over the next while, and reminds us that just about anybody could be the next recepient of a tropical cyclone, determined only by the steering at the time. This is much appreciated.
It isn't attached to the ITCZ?
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