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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Those trolls don't know sarcasm, they don't know who are the well respected and reliable, so they just go about causing trouble.
It is feeding time for the trolls, don't you know? The 5pm advisory came out and new model runs had come out... e.g. time to feed off of those of us who actually talk with interest (and intellect) about this stuff. The trick to losing them is not to feed them by quoting them or engaging in their worthless information that has no meteorological support or backing.
Good!
It is... if it verifies with GFS/ECMWF as an example, then a track through the Islands or a bit north of them will be a bit more in order than a track south of the Islands.
Yeah, 97L actually looks like something formidable at this stage. Look out below!
1306. thewildhourlychanges 8:54 PM GMT on August 19, 2011 +0
Quoting pottery:
And I was kidding about the Doom part.emily was rasing alot of eyebrows and gonna hit florida but nope to much dry air all around the atlantic and wind shear
but all models brought Emily out to sea,this time has been all consencus hitting USA
been a while that I have not seen those red block last time it was one small red block
post 1317
My teacher has a program where he can see everyone's laptop screen from his desk.. : /
FM FWC-N
BT
UNCLAS
MSGID/FWC-N/OVLY2/0087/AUG
OVLY/ATL STORM 08L/191200Z3/AUG/1OF1/TROP DEPRESSION 08L(08L)/METOC
TEXT/12//G/160000N7/0834200W7/D
TEXT/12//G/164200N3/0864800W6/S
TEXT/12//G/173000N1/0903000W2/D
TEXT/12//G/180000N9/0943000W6/D
LINE/4//G/160000N7/0834200W7/164200N3/0864800W6/1 73000N1/0903000W2
/180000N9/0943000W6
ARC/0/G///164200N3/0864800W6/045NM/045NM
TEXT/12//G/140000N5/0811200W2/TROP DEPRESSION 08L
TEXT/12//G/130000N4/0811200W2/19 AUG 1200Z
TEXT/12//G/120000N3/0811200W2/MAX 30 KT
TEXT/12//G/110000N2/0811200W2/275 AT 09 KT
TEXT/12//G/100000N1/0811200W2/34 KT RADII SHOWN
TEXT/12//G/090000N9/0861200W7/2100Z COMMENT:
TEXT/12//G/080000N8/0861200W7/ DISSIPATING AS A SIGNIFICANT
TEXT/12//G/070000N7/0861200W7/TROPICAL CYCLONE OVER LAND
TEXT/12//G/170000N8/0824800W2/2012Z MAX 40
TEXT/12//G/180000N9/0863000W7/2112Z MAX 30
TEXT/12//G/190000N0/0903000W2/2212Z MAX 20
ENDAT
BT
#0001
NNNN
WARNING ATCN MIL 08L NAT 110819150946
2011081912 08L NONAME 003 01 275 09 SATL 020
T000 160N 0837W 030
T012 163N 0850W 035 R034 035 NE QD 000 SE QD 000 SW QD 035 NW QD
T024 167N 0868W 040 R034 045 NE QD 020 SE QD 020 SW QD 045 NW QD
T036 171N 0886W 045 R034 050 NE QD 030 SE QD 030 SW QD 050 NW QD
T048 175N 0905W 030
T072 180N 0945W 020
AMP
036HR DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
048HR DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
072HR EXTRATROPICAL
NNNN
SUBJ: TROPICAL DEPRESSION NONAME (08L) WARNING NR 003
1. TROPICAL DEPRESSION NONAME (08L) WARNING NR 003
01 ACTIVE TROPICAL CYCLONE IN ATLANTIC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
191200Z --- NEAR 16.0N 83.3W
MOVEMENT PAST SIX HOURS - 275 DEGREES AT 09 KTS
POSITION ACCURATE TO WITHIN 020 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
WIND RADII VALID OVER OPEN WATER ONLY
REPEAT POSIT: 16.0N 83.3W
---
FORECASTS:
12 HRS, VALID AT:
200000Z --- 16.3N 85.0W
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 035 NM NORTHEAST QUADRANT
000 NM SOUTHEAST QUADRANT
000 NM SOUTHWEST QUADRANT
035 NM NORTHWEST QUADRANT
VECTOR TO 24 HR POSIT: 285 DEG/ 09 KTS
---
24 HRS, VALID AT:
201200Z --- 16.7N 86.8W
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 045 NM NORTHEAST QUADRANT
020 NM SOUTHEAST QUADRANT
020 NM SOUTHWEST QUADRANT
045 NM NORTHWEST QUADRANT
VECTOR TO 36 HR POSIT: 285 DEG/ 09 KTS
---
36 HRS, VALID AT:
210000Z --- 17.1N 88.6W
MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
RADIUS OF 034 KT WINDS - 050 NM NORTHEAST QUADRANT
030 NM SOUTHEAST QUADRANT
030 NM SOUTHWEST QUADRANT
050 NM NORTHWEST QUADRANT
VECTOR TO 48 HR POSIT: 285 DEG/ 09 KTS
---
EXTENDED OUTLOOK:
48 HRS, VALID AT:
211200Z --- 17.5N 90.5W
MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
VECTOR TO 72 HR POSIT: 280 DEG/ 10 KTS
---
72 HRS, VALID AT:
221200Z --- 18.0N 94.5W
MAX SUSTAINED WINDS - 020 KT, GUSTS 030 KT
WIND RADII VALID OVER OPEN WATER ONLY
EXTRATROPICAL
---
REMARKS:
191500Z POSITION NEAR 16.1N 84.0W. 48NM NW OF CABO GRACIAS A
DIOS, NICARAGUA. THERE ARE NO 12FT SEAS.
NEXT WARNINGS AT 192101Z, 200301Z, 200901Z AND 201501Z.//
BT
#0001
NNNN
0811081000 96N 135W 20
0811081006 98N 150W 20
0811081012 99N 165W 20
0811081018 100N 180W 20
0811081100 102N 195W 20
0811081106 104N 210W 20
0811081112 106N 228W 25
0811081118 108N 246W 25
0811081200 110N 265W 25
0811081206 112N 284W 25
0811081212 113N 300W 25
0811081218 113N 315W 25
0811081300 116N 326W 25
0811081306 117N 339W 25
0811081312 120N 370W 20
0811081318 122N 395W 20
0811081400 123N 425W 20
0811081406 125N 454W 20
0811081412 128N 481W 20
0811081418 130N 506W 20
0811081500 132N 529W 20
0811081506 134N 551W 20
0811081512 135N 573W 25
0811081518 136N 593W 25
0811081600 136N 613W 25
0811081606 137N 634W 25
0811081612 138N 654W 25
0811081618 141N 674W 25
0811081700 144N 694W 25
0811081706 147N 713W 25
0811081712 149N 733W 25
0811081718 151N 749W 25
0811081800 152N 766W 25
0811081806 153N 781W 25
0811081812 153N 794W 25
0811081818 154N 804W 30
0811081900 154N 818W 30
0811081906 155N 828W 30
0811081912 160N 837W 30
Cool.......Amazing how fall we have come since I was in school decades ago.
Have you tried out firefox 9, Taz?
Harvey wants to put on a little show this afternoon, doesn't he?
The dry air is there, but the dry SAL layer has diminished a little bit. Also, waves can moisten up the environment ahead of them, which is what 97L is currently doing. When the wave train begins up, the first few systems have to deal with dry air. However, now that we are in the heart of the season, the waves from the past actually benefits the waves currently moving off Africa.
A lot of the models didn't see the other systems because they were so small (spin-ups). However, 97L is completely different. All of the reliable models show 97L developing into something decent.
SAL Loop
All Active Year
Atlantic
99L.INVEST
97L.INVEST
08L.HARVEY
East Pacific
91E.INVEST
07E.GREG
Central Pacific
06E.FERNANDA
West Pacific
96W.INVEST
95W.INVEST
Indian Ocean
Southern Hemisphere
It's life, Jim, but not as we know it.
This just replaced CIMSS for me...
That is one pretty looking TS, though not for the residents of Honduras (and its islands), Belize, Guatemala and Mexico. Excellent banding on satellite. Time may be the only thing that prevents it from becoming a hurricane... but other than that, it is well on its way. If it doesnt become a hurricane, it will be so close to it.
Don't worry, I looked at the models for you.
cmc, gfs and nogaps all do not show westerly shear which is the main shear for cyclones. On top of that, the nogaps is the only one that shows the weakest wind shear. So if I were you, I would not trust just two models which show strong shear, and all 3 does not even show westerly shear.
1500 PM UTC advisory, by the way..
That was a less than sincere "Shucks"....I think you are Mocking me....:(
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.3
Tropical Cyclone Intensity Algorithm
----- Current Analysis -----
Date : 19 AUG 2011 Time : 201500 UTC
Lat : 16:28:41 N Lon : 84:35:39 W
CI# /Pressure/ Vmax
3.4 / 995.3mb/ 53.0kt
Final T# Adj T# Raw T#
3.4 3.5 3.8
notice the raw t and the final t are getting closer together...
Very impressive.
I actually looked at that one a couple of days back...good call Levi.
By the way Harvey is almost certainly going to become a hurricane in my opinion...upper air conditions are almost perfect and the surface circulation is extremely well defined already.
Invest 97L (TCFA soon):
Invests 98L and 99L (TCFA soon):
firefox 9 is not really out yet i will try it once it is out
Still could be with that weakness (ULL) to the NW of it!
19/1745 UTC 13.2N 49.0W TOO WEAK 97L
Watching it this evening should be fun. As it's passing 50W, we'll see what kind of dress rehearsal 97L puts on.
Viewing: 1351 - 1401
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