94L a threat to the Lesser Antilles; Gordon a hurricane; Helene hits Mexico
A large tropical wave that emerged from the coast of Africa Thursday night (Invest 94L) is located a few hundred miles southwest of the Cape Verde Islands off the coast of Africa, and is headed west at 15 - 20 mph. This storm is a threat to develop into a tropical storm that will affect the Lesser Antilles Islands as early as Wednesday. The storm is under moderate wind shear of 10 - 20 knots, and is over waters of 27.5°C. A large area of dry air lies just to the north of 94L, as seen on the latest Saharan Air Layer (SAL) analysis. This morning's 8:15 am EDT ASCAT pass caught the east side of 94L, and showed a partial surface circulation. Satellite images show just a modest amount of heavy thunderstorm activity, and I expect the earliest that 94L could develop into a tropical depression would be Sunday.
Figure 1. Morning satellite image of Invest 94L.
Forecast for 94L
The latest 8 am EDT run of the SHIPS model predicts that wind shear will be low, 5 - 10 knots, and ocean temperatures will gradually warm from 27.5°C to 28.5°C over the next four days, as 94L tracks westwards towards the Lesser Antilles. As is typical with storms making the crossing from Africa to the Antilles, dry air to the north will likely interfere with development. However, with shear expected to be low, dry air may be less of an issue for 94L than it was for Ernesto or TD 7. The storm should maintain a nearly due west track through Monday night, to a point near 50°W, about 700 miles east of the Lesser Antilles. At that point, a trough of low pressure passing to the north of 94L may be able to pull the storm more to the northwest, as suggested by the latest 06Z (2 am EDT) run of the NOGAPS model, and by three members of the GFS model ensemble forecast (Figure 2.) However, the models have been trending more towards a solution where this trough is not strong enough to influence 94L's path. This scenario will be more likely if 94L takes its time to develop, since a weaker storm will be smaller and shallower, and less likely to respond to the trough passing to the north. Our two best performing models, the GFS and ECMFW, both take 94L through the Lesser Antilles. The ECMWF, which predicts that 94L will stay weak and not develop, is faster, bringing the storm through the Lesser Antilles on Wednesday. The GFS model is slower, bringing 94L to the Lesser Antilles on Thursday as a hurricane. The models have shown poor run-to-run consistency in both the timing and the track of 94L, so it is difficult to assess which land areas might be most at risk, and when. A database of historical probabilities of storms in the same location as 94L maintained by Dr. Bob Hart of Florida State University reveals that historically, 45% of storms in this location have eventually hit land, with Canada (13% chance) and North Carolina (15% chance) the most likely targets. In their 8 am EDT Tropical Weather Outlook, NHC gave 94L a 40% chance of developing into a tropical depression by Monday morning.
Figure 2. The 00Z (8 pm EDT) run of the GFS model from August 17, 2012, was done 20 different times at low resolution using slightly different initial conditions to generate an ensemble of forecasts (pink lines.) The high-resolution operational GFS forecast is shown in white.
Gordon becomes a hurricane
Hurricane warnings are flying for the central and eastern Azores Islands as Hurricane Gordon heads eastwards at 18 mph. Gordon became the third hurricane of the 2012 Atlantic hurricane season at 5 am Saturday morning, and is sporting an impressive-looking eye on visible satellite loops. Gordon should be able to maintain hurricane status until Sunday, when wind shear will rise steeply to 30 - 40 knots, and ocean temperatures will drop to 25°C. The combined effects of high wind shear, dry air, and cooler waters will likely act to weaken Gordon to a strong tropical storm by the time it arrives in the Azores Islands Sunday night, but the storm will be strong enough to bring damaging winds and heavy rain to the Azores Islands. Gordon is not a threat to any other land areas, and the extratropical remnants of Gordon will not bring any strong winds or significant rain to Europe. The last time the Azores were affected by a tropical storm was in 2009, when Tropical Storm Grace brought 65 mph winds on October 4. No significant damage was reported. Ironically, the last hurricane to affect the Azores was the 2006 version of Hurricane Gordon, which caused minor damage in the Azores, consisting of mostly fallen trees and power outages. However, after Gordon became an extratropical low, four injuries due to falling debris from high wind were reported in Spain, and Gordon brought high winds and rain that affected practice rounds at the Ryder Cup golf tournament in Ireland. About 126,000 homes were without power after the storm in Northern Ireland and one injury was reported.
Figure 3. Morning satellite image of Hurricane Gordon.
Helene makes landfall in Mexico
Tropical Storm Helene made landfall near 10 am EDT as a tropical storm near Tampico, Mexico, with 40 mph winds. Helene's formation on August 17 ties 2012 with 1933 for the 2nd earliest appearance of the Atlantic's eighth tropical storm. Helene's rains should remain south of Texas, but moisture from Helene may feed into a stalled frontal system over the northern Gulf of Mexico and bring heavy rains to the northern Gulf Coast early next week.
I'll have a new post this afternoon, giving a quick global weather summary for July, the 4th hottest July in Earth's history.
Jeff Masters
Reader Comments
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And this explains why: AL08 18August6pm 34.0n3.75w 90knots 969millibars
But it says 'Helene' on the header.... and there is nothing.
Only 2 hurricanes to become major north of 38 N
What's been done to deserve crow lol.
I remember last year, the GFS had Irene going up or near the spine of FL on at least 10 consecutive runs, maybe more. . . and we all know where it ended up. So, it is always a wait and see, but fun to track and speculate.
Can anyone tell me why (if it's true) the 00z and 12z are considered better and more accurate model runs?
AL, 94, 2012081818, , BEST, 0, 133N, 320W, 25, 1008, DB
The storm was flirting with 90 mph at 11 am AST, and 105 mph at 2pm AST. I honestly have no clue why Brennan was so conservative in the intermediate.
They're even more conservative than usual in the intermediates.
Euro is blank at 192 hours:
Not an impossible scenario, but probably unlikely. Models have been trending weaker though, at least short term.
Well, people here who say things like that are wrong. It's doubtful that Gordon currently has winds anywhere near 115 mph, and it's going to weaken very rapidly over the next 24 hours. By the time it gets to the Azores, maybe 65 mph, and the Azores get winter storms wth winds in that range on a regular basis.
A 180 NM RADIUS OF 17.4N 124.8E WITHIN THE NEXT 12 TO 24 HOURS.
AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE OF NUMBERED TROPICAL
CYCLONE WARNINGS AT THIS TIME. WINDS IN THE AREA ARE ESTIMATED TO
BE 15 TO 20 KNOTS. METSAT IMAGERY AT 181730Z INDICATES THAT A
CIRCULATION CENTER IS LOCATED NEAR 18.5N 124.8E. THE SYSTEM IS
MOVING SOUTHWARD AT 06 KNOTS.
2. REMARKS: THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 19.0N
124.8E, IS NOW LOCATED NEAR 18.5N 124.8E, APPROXIMATELY 315 NM
NORTHEAST OF MANILA, PHILIPPINES. RECENT ANIMATED ENHANCED INFRARED
(EIR) SATELLITE IMAGERY SHOWS DEEP CONVECTION BUILDING OVER THE
SOUTHERN AND EASTERN SECTORS OF A WELL-DEFINED LOW-LEVEL CIRCULATION
CENTER (LLCC). THE EIR, ALONG WITH A SERIES OF SSMIS IMAGES (180929Z
AND 180933Z) SHOW A NOTICEABLE LACK OF DEEP CONVECTION OVER THE
NORTHWESTERN PORTION OF THE LLCC. UPPER-LEVEL ANALYSIS INDICATES THE
DISTURBANCE IS LOCATED A COUPLE OF DEGREES POLEWARD OF THE NEAR
EQUATORIAL RIDGE AXIS. ADDITIONALLY, MULTIPLE TROPICAL UPPER-
TROPOSPHERIC TROUGH (TUTT) CELLS CAN BE SEEN A FEW DEGREES NORTH AND
NORTHWEST OF THE LLCC. ANOTHER LARGER TUTT CELL RESIDES FURTHER TO
THE EAST, SOUTH OF JAPAN. THIS COMPLEX UPPER-LEVEL ENVIRONMENT IS
CAUSING CONVERGENCE OVER THE WESTERN SECTOR OF THE LLCC AND
FAVORABLE DIVERGENCE OVER THE EASTERN PORTION. VERTICAL WIND SHEAR
IS ESTIMATED AT 10-15 KNOTS FROM THE NORTH. DURING THE NEXT COUPLE
OF DAYS THE SMALLER TUTT CELLS SHOULD TRACK OFF TO THE WEST AND
POLEWARD OUTFLOW MAY BECOME CONNECTED TO THE LARGER TUTT CELL WHICH
RESIDES FURTHER TO THE EAST. THIS SHOULD CAUSE UPPER-LEVEL
CONDITIONS TO GRADUALLY IMPROVE AND ALLOW THE SYSTEM TO FURTHER
INTENSIFY. CURRENTLY, AN 181334Z ASCAT PASS INDICATES A LARGE FIELD
OF 20 KNOTS OVER THE WESTERN PORTION OF THE LLCC. SEA SURFACE
TEMPERATURES ARE FAVORABLE FOR TROPICAL CYCLONE DEVELOPMENT RANGING
FROM 26-29 DEGREES CELSIUS. THE DISTURBANCE IS EXPECTED TO SLOWLY
DRIFT EQUATORWARD DURING THE NEXT 24 HOURS BEFORE MAKING A POLEWARD
TURN THEREAFTER. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 15
TO 20 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1006
MB. DUE TO IMPROVED CONSOLIDATION OF THE LLCC AND DEEP CONVECTION,
ALONG WITH THE EXPECTED IMPROVEMENT IN UPPER-LEVEL CONDITIONS, THE
POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE
WITHIN THE NEXT 24 HOURS IS HIGH.
End of The Season....
LOL
Yes,but when irene ,the storm changes the COC to other to the North of PR, i remember tha.....t is a difference system
Bust season. :P
They're only trending weaker because of land interaction from what I've seen.
Link
Is that official?
Wow, it looks very good. Hope that the Azores get prepared.
yes
Can anyone please explain why hasn't HRWF & GFDL jumped on 94L yet..? Nothing on the model pages!!
Ok thx. Hmm 80-105... RI?
What about Ophelia 11'?
Yes that is official. Latest T-number is a 5.0. That is 90kts or 104 mph.
there is a 14% chance of a landfalling storm...94L !
an Irene story part II?
Yes, but that is for Tropical Depression Helene, not Invest 94L.
I think I'll go with the Euro.
Dissipation is Good!
did you expect the Gordon to become a hurricane to start with???
They should. The people in the Azores are expecting no more than a low end Cat 1, and now he's just 10 kts off from major hurricane status... They need to know about that.
Yes, that's for sure, but all systems and circumstances around them are different from one to the other. But those dozen or so nearly identical model runs had me a believer with Irene.
His spin has almost stopped, think he gorged on to much moist air, ha. Now he'll just slowing waddle on north to hopefully take his leftover moisture to drought stricken regions.
Nobody cares.
They contain upper air observations from the release of ballons at various sites around the world, although that does not help much in the middle of the Atlantic since no model cycles have upper air data from there (other than obs from airplanes).
????
00Z and 12Z get direct data input. The other two are extrapolated.
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