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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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.
I like being outdoors at night when I can. Battling mosquitoes is the biggest bummer around here though. But we have a favorite fishing pier we go to at night. There's usually enough of a breeze to keep the critters at bay. I can sit there and happily contemplate the stars for hours. :)
just sayin'
There are no absolutes in meteorology, or I would.
I think it's common knowledge that to be dogmatic is foolish with these kinds of things.
Nice explanation. :)
Agreed, which is why I'm trying desperately to not be dogmatic.
Anytime you see me forecast, you will never see me posit an absolute.
WTNT43 KNHC 200854
TCDAT3
TROPICAL STORM HARVEY DISCUSSION NUMBER 6
NWS NATIONAL HURRICANE CENTER MIAMI FL AL082011
400 AM CDT SAT AUG 20 2011
AFTER A LULL BETWEEN 0400 AND 0600 UTC...DEEP CONVECTION HAS
RE-BLOSSOMED NEAR THE ESTIMATED CENTER OF HARVEY...WHICH IS VERY
NEAR ROATAN ACCORDING TO A FEW SURFACE OBSERVATIONS ON THAT ISLAND.
SINCE THE CONVECTIVE STRUCTURE LOOKS SIMILAR TO THE STRUCTURE WHEN
THE LAST HURRICANE HUNTER MISSION WAS INVESTIGATING THIS SYSTEM...
THE INITIAL INTENSITY WILL BE MAINTAINED AT 50 KT. ANOTHER RECON
MISSION IS SCHEDULED TO REACH HARVEY AROUND 1200 UTC.
BASED ON THE ROATAN OBSERVATIONS...HARVEY MAY HAVE PICKED UP SOME
SPEED...AND ITS INITIAL MOTION IS ESTIMATED AT 275/10. THE
SUBTROPICAL RIDGE TO THE NORTH OF THE CYCLONE IS EXPECTED TO
CONTINUE STEERING HARVEY ON A NEARLY CONSTANT WESTWARD HEADING UNTIL
DISSIPATION IN 72 HOURS. THE NEW OFFICIAL FORECAST IS JUST A LITTLE
SOUTH OF THE PREVIOUS ONE AND GENERALLY LIES NEAR THE GFS...
ECMWF...AND THE MULTI-MODEL CONSENSUS TVCA.
ENVIRONMENTAL CONDITIONS ARE STILL EXPECTED TO BE CONDUCIVE FOR SOME
STRENGTHENING BEFORE HARVEY REACHES THE COAST OF BELIZE LATER
TODAY. THE STATISTICAL SHIPS AND LGEM MODELS ARE THE HIGHEST OF
THE INTENSITY GUIDANCE AND INDICATE THAT HARVEY COULD BE JUST BELOW
HURRICANE STRENGTH AT 12 HOURS. SINCE LANDFALL ON THE OFFICIAL
FORECAST TRACK WOULD BE WITHIN THE 12 TO 18 HOUR PERIOD...IT IS
STILL POSSIBLE THAT HARVEY COULD BECOME A HURRICANE JUST BEFORE
MOVING INLAND ACROSS THE COAST OF BELIZE EVEN THOUGH NOT EXPLICITLY
SHOWN IN THE OFFICIAL FORECAST. IN FACT...THERE IS A 1 IN 3 CHANCE
OF THAT OCCURRING...BASED ON THE CURRENT FORECAST AND RECENT NHC
INTENSITY ERRORS. WEAKENING IS EXPECTED AFTER HARVEY MOVES
INLAND...AND THE NHC INTENSITY FORECAST FROM 24 HOURS AND BEYOND
FOLLOWS THE DECAY OF THE STATISTICAL MODELS. DISSIPATION IS NOW
EXPECTED BY 72 HOURS.
BASED ON THE UPDATED FORECAST TRACK...THE GOVERNMENT OF GUATEMALA
HAS UPGRADED THE TROPICAL STORM WATCH TO A TROPICAL STORM WARNING
ALONG THE GUATEMALAN COAST.
FORECAST POSITIONS AND MAX WINDS
INIT 20/0900Z 16.4N 86.5W 50 KT 60 MPH
12H 20/1800Z 16.5N 87.7W 60 KT 70 MPH
24H 21/0600Z 16.7N 89.6W 50 KT 60 MPH...INLAND
36H 21/1800Z 16.9N 92.0W 35 KT 40 MPH...INLAND
48H 22/0600Z 17.2N 94.6W 25 KT 30 MPH...INLAND
72H 23/0600Z...DISSIPATED
$$
FORECASTER BERG/STEWART
Agree
Location: 16.4°N 86.5°W
Max sustained: 60 mph
Moving: W at 12 mph
Min pressure: 994 mb
And Gustav was a bad storm. I was out of power for over a week. I had 4 neighbors with trees laying in their houses. Most of my trees were down with 1 just missing my house. My yard had over a foot of water in it from the rain that caused the Amite river to flood, which had all of our drainage ditches backed up.
pressure is going like down....
The second being the more interesting question.
No problem here, Aspectre. If you can see this. :)
I have to agree, it does have some banding however, with may be making the NHC to jump the gun a bit.
Hope they do soon.
CARIBBEAN SEA AND TROPICAL N ATLC S OF 22N W OF 55W...TROPICAL
STORM HARVEY WAS CENTERED NEAR 16.2N 85.2W AT 03Z...OFF THE N
CENTRAL COAST OF HONDURAS. CLUSTERS OF STRONG CONVECTION ARE
NOTED ON SATELLITE IMAGERY NEAR THE CENTER OF HARVEY. THE
STORM WILL TRACK W THROUGH THE GULF OF HONDURAS...INTENSIFYING
TO HURRICANE STRENGTH BRIEFLY BEFORE MOVING INTO BELIZE BY LATE
SAT. REFER TO WTNT23 KNHC/TCMAT3 FOR FURTHER DETAILS AND UPDATES
ON TS HARVEY.
They must have. Even I'm starting to get sleepy. :)
However, if the models spit out runs that bring it close to home or even a direct hit, they all say weellll the models aren't always correct, they have huge errors this far out and there's lots of time to watch it. Geez, stop positive casting and just tell it like it is guys.
Hey since I started all this, no offense to the local tv wx folks, the service you provide is invaluable, just makin an amusing non-professional observation. :-)
FURTHER EAST MODEL CONSENSUS SHOWS A
DEVELOPING LOW PRES APPROXIMATELY 450 NM E OF GUADELOUPE NEAR
14N53W TO MOVE THROUGH THE LEEWARD ISLANDS THIS
WEEKEND...POSSIBLY AS A TROPICAL CYCLONE...THEN TOWARD
HISPANIOLA BY LATE MON. FOR NOW...THIS FEATURE IS EXPECTED TO
ELEVATE WINDS TO 30 KT WITH SEAS TO 13 FT OVER THE NE CARIBBEAN
STARTING LATE SUN THROUGH TUE. MARINERS AND INTERESTS FROM THE
LEEWARD ISLANDS TO HISPANIOLA SHOULD CONTINUE TO MONITOR THE
DEVELOPMENT AND MOVEMENT OF THIS LOW PRES OVER THE NEXT SEVERAL
DAYS.
I know right? Its ridiculous, they do it all the time. Just tell it the way it is..
MARINE WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
330 AM EDT SAT AUG 20 2011
MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA
AND TROPICAL N ATLC...AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W.
GULF OF MEXICO...
A SURFACE RIDGE EXTENDING FROM N FLORIDA THROUGH TEXAS WILL
REMAIN IN PLACE THROUGH SAT...THEN WEAKEN SLIGHTLY SUN AND MON
AS A WEAK FRONTAL BOUNDARY PUSHES THROUGH THE TENNESSEE VALLEY
AND STALLS. WINDS AND SEAS WILL REMAIN MINIMAL OVER THE NORTHERN
HALF OF THE GULF INTO EARLY NEXT WEEK. FURTHER SOUTH...THE
REMNANTS OF TROPICAL STORM HARVEY WILL MOVE THROUGH SOUTHERN
MEXICO THIS WEEKEND...MAINTAINING MODERATE EASTERLY FLOW OVER
MUCH OF THE SOUTHERN GULF.
N ATLC S OF 31N W OF 55W...
A SURFACE RIDGE EXTENDING FROM BERMUDA TO N FLORIDA WILL REMAIN
IN PLACE ALONG 28N TO 29N THROUGH TUE. MEANWHILE MODEL CONSENSUS
SHOWS A DEVELOPING LOW PRES NEAR 14N53W TO MOVE THROUGH THE
LEEWARD ISLANDS THIS WEEKEND...POSSIBLY AS A TROPICAL
CYCLONE...THEN TOWARD HISPANIOLA BY LATE MON...AND TOWARD THE
SOUTHERN BAHAMAS BY LATE TUE. MODERATE TO FRESH WINDS S OF 25N
WILL START TO INCREASE TO 20 TO 25 KT N OF PUERTO RICO BY LATE
SUN...WITH SEAS BUILDING TO 8 TO 12 FT...SPREADING W THROUGH THE
SOUTHERN BAHAMAS MON INTO TUE WITH WINDS UP TO 30 KT. MARINERS
AND INTERESTS IN THE SOUTHERN BAHAMAS AND TURKS AND CAICOS
SHOULD CONTINUE TO MONITOR THE DEVELOPMENT OF THIS LOW OVER THE
NEXT SEVERAL DAYS.
You certainly know your way around!
One of our locals said there would be no cyclones in the gulf for the next month and a cold front was going to come through on September 10th bringing an early end to our hurricane season. Lol. Gotta love em.
edit:talking about NWS, 97L could very well make it into the eastern GOMEX, wouldnt bet on it atm, but it could
LOL "simplest simpletons". Thats not a nice way to refer to fellow bloggers, now is it? LOL...
Simpletons? Ya just had to make it personal, didn't you?
:D
HEY! That didn't sound right. :p lol. I might have been offended if I didn't want to mention those models you just showed lookin' a little better for Florida. Lets hope they keep moving out.
yes having the same problem. have to refresh it like 3 times before the whole page will display.
Ah they'll go back west. Then they'll go back east. I don't put much stock in them more than 2 to 3 days out.
Lol, I agree some are like that, but what makes it really bad is that most of those who do it have been on the air for a long time and are really good...I just can't stand positive casting. Wx is a science so they need to be factual and stop trying to find the "good news"...I can hear them now, The tstorm today had a wind gust to 95, but the good news is it was under 100!! Lol
WEDNESDAY THROUGH FRIDAY...THERE STILL TO MUCH UNCERTAINTIES
DURING THIS PART OF THE FORECAST. PRACTICALLY ALL LONG RANGE MODELS
CONTINUE TO FORECAST THE DEVELOPMENT OF A STRONG TROPICAL WAVE,
CURRENTLY EAST OF THE LESSER ANTILLES, AND MOVE IT WEST- NORTHWEST
POSITIONING IT IN OUR VICINITY DURING THIS PERIOD. DUE TO THESE
UNCERTAINTIES, AND THE FACT THAT THE SYSTEM HAS NOT DEVELOPED
YET, DECIDED TO CONTINUE TO KEEP THE "STATUS QUO" AND GO CLOSER TO
CLIMATOLOGY FOR THIS PERIOD. ALL INTEREST IN SOUTH FLORIDA SHOULD
CONTINUE TO MONITOR THE PROGRESS OF THIS SYSTEM THE NEXT FEW DAYS AS
IT MOVES WESTWARD THROUGH THE CARIBBEAN.
I'm just cutting and pasting the facts, Sir. Lol.
you still working. But I'm not sure what's happening, it's definitely got some issues right now
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