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
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 | 91 | 92 — Blog Index
Way too soon to be expressing compassion....save it
Yeah, I don't think it has a defined LLC as of now.
Yes..looking better for Florida all the time...
HA! You shoulda been here last night? I forget. But it was brutal. But I think that was only a select few Texas haters. And to all I apologize for feeding the trolls. Won't happen again. :)
u being sarcastic
Not at all. If current trends continue the system could miss Florida altogether...
Woah man, you're definitely learning your stuff. Good to see that the blog can actually help people rather than cause headaches, lol. Anyways, I agree. Timing, as usual, will be one of the main key factors as to whether 97L affects us here in south Florida, or if it ventures off towards the west or east.
Anytime you have a "public" domain you are going to have a great deal of riff-raff..
The 4 longer line-segments represent TropicalStormHarvey's path and
the shorter westernmost line-segment is the straightline projection.
Using straightline projection of the travel-speed&heading derived from the ATCF coordinates spanning the 6hours between 12amGMT then 6amGMT :
TS.Harvey's travel-speed was 11.3mph(18.2k/h) on a heading of 281.8degrees*(WNW)
TS.Harvey was headed toward passage over RoatanIsland,Honduras ~1&1/2 hours from now
Copy&paste sjx, mdb, 15.7n82.7w-16.0n83.3w, 16.0n83.3w-16.1n84.0w, 16.1n84.0w-16.1n84.7w, 16.1n84.7w-16.3n85.7w, rtb, 16.1n84.7w-16.413n86.275w into the GreatCircleMapper for more info
The previous mapping (for 20August_12amGMT)
* 281.25degrees is halfway between West and WestNorthWest
what trend u mean the models
You are one of the most respectful and kind people here. We need more like you!
Well yes. Just hours ago many of the models had it entering the Gulf. That trend...
Oh, um. Thank you. :)
That would be best for everyone if it would just curve out east/north of the islands. And I hope it will. I think if it deepens quickly it might. Although I believe they've been saying better conditions are farther west unfortunately. This is a recap of or average of the models.
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
338 AM EDT SAT AUG 20 2011
VALID 12Z WED AUG 24 2011 - 12Z SAT AUG 27 2011
MODELS DEPICT A SLOWLY EVOLVING LONGWAVE PATTERN OVER NORTH
AMERICA DURING THE UPCOMING MEDIUM RANGE PERIOD...WITH AN
UNUSUALLY STRONG MID LEVEL HEIGHT ANOMALY REMAINING NEARLY
STATIONARY OVER THE DAVIS STRAIT AND GREENLAND...WHICH THEN FAVORS
UPPER TROUGHS LINGERING FROM HUDSON BAY SOUTHWARD TO THE GREAT
LAKES AND FROM ALASKA ACROSS THE NORTHEAST PACIFIC. DAY-TO-DAY
DIFFERENCES ARE ABOUT AVERAGE STARTING DAY 3/TUE...BUT QUICKLY
BECOME LARGE SURROUNDING THE STRONG AND COMPLEX UPPER TROUGH OVER
THE GULF OF ALASKA...AND ALSO IN THE CARIBBEAN SEA/GULF OF MEXICO
DUE TO INCREASINGLY DIFFERENT TRACK FORECAST FOR THE TROPICAL WAVE
CURRENTLY ENTERING NEARING THE LEEWARD ISLANDS. TO ADDRESS THESE
INCREASINGLY LARGE DIFFERENCES...WILL LIKELY TRANSITION QUICKLY TO
EITHER THE 00Z GEFS MEAN AND/OR ECMWF ENSEMBLE MEAN FOR THE
PRELIMINARY PRESSURES/FRONTS FOR DAYS 3-7. MODELS HAVE TRENDED
SLIGHTLY TO THE RIGHT OF PRIOR FORECASTS WITH THE TROPICAL WAVE
NEARING THE LEEWARD ISLANDS WITH THE 00Z OPERATIONAL ECMWF CLOSEST
TO THE DETERMINISTIC CONSENSUS AND GLOBAL ENSEMBLE MEANS.
MEANWHILE..THE 00Z GFS IS SLIGHTLY TO THE RIGHT AND FASTER WITH
THE UKMET/CANADIAN TO THE LEFT BRINGING THE WAVE INTO THE CENTRAL
GULF OF MEXICO BY NEXT FRIDAY. FOR NOW...WILL USE THE LATEST
COORDINATION POINTS AGREED UPON FROM THE NHC AND EXTRAPOLATE ONE
DAY FORWARD FOR THE NEW DAY 7 POINT...WHICH WILL PLACE IT IN THE
EASTERN GULF ON SATURDAY WHICH IS JUST LEFT OF THE 00Z ECMWF
POSITION.
???
Hi RG. They were asking about you earlier. Glad you're ok. Thanks for the update. And stay safe!
In terms of a gulf entry...
Thank you for informing us how's everything over there.
Stay safe!
Still to early to tell I guess. If I had to pick an area based on numerous model runs over the last 5 days or so, I would say somewhere between the Central Bahamas and extreme eastern GOM. JMO. So I guess overall it would be the florida area and trust me, I am borderline "downcaster" and DONT want a storm. I am just trying to be objective but really still early.
You seem very balanced. I am a downcaster as well....
Have you always been a night owl or is it just during the season?
Well, this economy is so bad and so fragile, pretty much everywhere. I simply dont think most people need a hurricane in their life right now. Roofers wouldn't mind though! I have found that roofers tend to be upcasters..LOL. Of course any bad storm can be a nightmare for those in the islands. Not to mention real killers.
70%??
The NHC has given out some eyebrow raising 48 hr percentage figures this season, like the 'near 100%' that turned out to be wrong.
Just looks a mess to me.
Lol. Pretty much always been. I'd say my brain thinks it lives in Australia but that wouldn't explain why I stayed up nights in Germany. :) But right now my husbands working the night shift. All the kiddies are grown. So we're finally on my time! Lol. Until he goes back on days in October.
Are you a night owl as well? Or are these models rattling you a bit? They would me. They have shown unusual consistency.
BTW, You are a nice, level-headed asset to the blog as well. Sorry the compliment through me for a sec there. :)
I agree. But it will likely get together some pretty soon. Your right though. You would think approaching late august a wave such as this would be much further along. All of the systems so far have looked crappy. I think 97 is already carrying a low pressure of 1005mb. Thats not to shabby. It seems systems are having a rough time at the surface.
If it tracks right thru the island it is likely to be greatly reduced in intensity and structural organization when it exits. Its true, even some of the most powerfull hurricanes ever (david Cat 5) never remotely regained their previous intensity levels after exiting.
That's what I've always heard. I don't know an example of it off the top of my head to show you though. Gustav and Ike tangled with some of the islands and were much less potent in the gulf at landfalls. Though they had longer over water than is being shown with 97l. Even though they were only 2's they were both unusually strong for a cat 2. Sigh. Lets hope 97l stays weak.
I see you are right in the middle of it now.
Be safe!
It shouldn't be too strong when it reaches Hispaniola. Weaker systems can fare better given that they lack inner cores.
Additionally, the environment appears favorable enough so that land might not disrupt it as much as would ordinarily be expected. A counteracting, if you will.
I guess will just have to wait and see
GOOD! :)
2 prime examples would be David in 1979. A powerful category 5 hurricane killing over 2000 people in the islands. Went on to skirt south florida going ashore central florida as a min weak disorganized cat 2 hurricane. Also Cleo 1964. A deadly cat 4 hurricane in the islands. Went on to go up floridas east coast, but as a respectable cat 2. Still nothing like it had been. There are also examples of storms that near completely fell apart. Alot depends on forward motion and the size of the circulation of the storm as it goes over the islands. Of course exactly which area of the islands it has to contend with is also a major factor.
Thank you for your kind words and encouragement. I am a night owl naturally. I enjoy the late hours both indoors and outdoors. I live in a very remote area in the woods and the combination of fog and a bright moon with clouds drifting by is a wonderful thing to behold. Good to hear you have time for yourself to enjoy.
In short, it might (emphasis on "might", as we still do not know how much land this is going to interact with) allow the US to escape the full brunt of it, but a hurricane is still a possibility.
Still a lot of variables though, all things considered.
morning rounds complete; back to sleep.
So the potential to disrupt systems is there. And that's a little encouraging for people n the U.S. I hope it's not particularly strong or wet for the islands either. The MJO being back around may not bode well. But then again I think we got a few of our systems when the mjo wasn't around. Strange things this year. We'll have to wait and see.
Viewing: 3501 - 3551
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 | 91 | 92 — Blog Index