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
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In an area of greatest TCHP no less... could get interesting.
This does seem to be the middle most area of the models so far. I am curious if the ECMWF sticks to that run in the furture. Or if it will have it flop back and fourth in the future.
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.3
Tropical Cyclone Intensity Algorithm
----- Current Analysis -----
Date : 19 AUG 2011 Time : 174500 UTC
Lat : 16:10:01 N Lon : 84:05:06 W
CI# /Pressure/ Vmax
3.2 / 998.0mb/ 49.0kt
Final T# Adj T# Raw T#
3.2 3.5 3.6
000
NOUS42 KNHC 191555
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1155 AM EDT FRI 19 AUGUST 2011
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 20/1100Z TO 21/1100Z AUGUST 2011
TCPOD NUMBER.....11-080
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
2. TROPICAL DERESSION EIGHT
FLIGHT ONE -- TEAL 76
A. 21/0000Z
B. AFXXX 0608A CYCLONE
C. 20/2015Z
D. 17.0N 88.00W
E. 20/2330Z TO 21/0300Z
F. SFC TO 10,000 FT
3. OUTLOOK FOR SUCCEEDING DAY:
A. BEGIN 6-HRLY FIXES ON WHAT IS NOW THE SUSPECT
AREA IF IT DEVELOPS AT 21/1200Z.
B. POSSIBLE G-IV SURVEILANCE MISSION FOR THE
SAME SYSTEM AT 22/0000Z.
II. PACIFIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. SUCCEEDING DAY OUTLOOK.....NEGATIVE.
JWP
thank you
1. SUSPECT AREA (CARIBBEAN)
FLIGHT ONE -- TEAL 74
A. 20/0000Z
B. AFXXX 0408A CYCLONE
C. 19/2030Z (August 19/4:30 PM EDT)
D. 16.4N 85.0W
E. 19/2330Z TO 20/0300Z
F. SFC TO 10,000 FT
FLIGHT TWO -- TEAL 75
A. 20/1200Z,1800Z
B. AFXXX 0508A CYCLONE
C. 20/0830Z (August 20/4:30 AM EDT)
D. 16.6N 86.80W
E. 20/1130Z TO 20/1730Z
F. SFC TO 10,000 FT
2. OUTLOOK FOR SUCCEEDING DAY:
A. CONTINUE 6-HRLY FIXES ON CARIBBEAN SYSTEM
UNTIL LANDFALL.
B. POSSIBLE LOW LEVEL INVEST AT 20/1800Z NEAR
15.0N 53.0W
3. REMARK: TASKING FOR 19/1800Z ON TCPOD 11-078 HAS
BEEN SLIPPED TO 20/0000Z AS SHOWN ABOVE.
C. 20/1615Z = 12:15 EST (is this right?)
I don't think this is for 97L
First post and I give an instant poof.
Bahamas is definitely not out of the hunt, just yet.
1. SUSPECT AREA (CARIBBEAN)
FLIGHT ONE -- TEAL 74
A. 20/0000Z
B. AFXXX 0408A CYCLONE
C. 19/2030Z
D. 16.4N 85.0W
E. 19/2330Z TO 20/0300Z
F. SFC TO 10,000 FT
The plane is scheduled to take off at 4:30 PM EDT (C)
The plane is scheduled to arrive in the vacinity of the storm at 7:30 PM EDT and stay untill 11:00 PM EDT (E)
The plane is scheduled to do a center fix at 8:00 PM EDT (A)
Where is Florida in that run?
I cant see it because of some sort of dart board thingy in the way.
Oh its going to be a long week.
Forgive me folks,If I cant find humor in things I start to worry.
Other than proximity to land, what are any other road blocks that should keep him from becoming a hurricane?
They changed A. but forgot to change C. C is the time the mission ENDS. A is the time the mission is to start. So next one starts at 0000z or 8pmET and should end 2 1/2 hours later. Typo on their part. See remark 3.
like: "holy mackerel"?
As Keeper keeps posting, best guide this far out is 500 mb vorticity.
Now to just lock on to landfall...
Swift intensification?
been wunderin' 'bout dis all day....Anybody have any insight?
What are your thoughts on the results of a "Computer Model" predicting a storm with the pressure at 970 MB?
The fact that the model is lowering the pressure to that level doesn't actually show that the actual "pressure" at landfall will probably be lower.
Oh I give up. Now I'm confused. Guess we'll find out in a few hours lol
What are the T numders like the 3.5 in one of the posts above?
my gut has been telling me that 98L will be a "Monster" but that few land areas will probably be effected (Unless you count Bermuda and the Azores). However, I have been wondering if the computer models might be wrong and it winds up going firther west than they are saying.
50 too 60KT storm
yup
CMC phase diagram interesting. East coast development shows some subtropical characteristics.
Link
Really has it strengthening after going over hispaniola.
(knots) (mph) (km/h) Atlantic NW Pacific
1.0 - 1.5 25 29 46 TD ---- ----
2.0 30 35 56 TD 1009 1000
2.5 35 40 65 TS 1005 997
3.0 45 52 83 TS 1000 991
3.5 55 63 102 TS 994 984
4.0 65 75 120 Cat 1 987 976
4.5 77 89 143 Cat 1–2 979 966
5.0 90 104 167 Cat 2–3 970 954
5.5 102 117 189 Cat 3 960 941
6.0 115 132 213 Cat 4 948 927
6.5 127 146 235 Cat 4 935 914
7.0 140 161 260 Cat 5 921 898
7.5 155 178 287 Cat 5 906 879
8.0 170 196 315 Cat 5 890 858
Note: The pressures shown for the NW Pacific are lower as the pressure of that whole environment is lower as well.
Link
It's probably RI.
3.5 Dvorak=55kts or 65mph(or 100kph)
"SEE SPECIAL FEATURES SECTION FOR DETAILS ON THE TROPICAL WAVES.
...THE ITCZ/THE MONSOON TROUGH...
THE ACTIVE TRPCL WAVE OVER THE FAR ERN TRPCL ATLC HAS SPLIT
THE MONSOON TROUGH. ONE SECTION REMAINS INLAND OVER
AFRICA...WHILE THE OTHER CONTINUES ON THE W SIDE OF THE TRPCL
WAVE ALONG 13N22W 11N35W TO THE TRPCL WAVE IN THE CENTRAL TRPCL
ATLC NEAR 13N48W. CONVECTION NEAR THE MONSOON TROUGH HAS BEEN
ASSOCIATED WITH THE TROPICAL WAVES AND IS DISCUSSED IN THE
SPECIAL FEATURES SECTION."
Don't worry... enjoy this weekend! Come Monday, it'll be alright. They will have more of an idea by Tuesday where this will end up, I am sure. It is just so hard to tell right now with this not even being a developed system yet.
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