Tropical Storm EARL Post#1 has all the graphics

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8pm

A BROAD AREA OF LOW PRESSURE LOCATED ABOUT 125 MILES SOUTHWEST OF
THE CAPE VERDE ISLANDS IS ACCOMPANIED BY A LARGE AREA OF CLOUDINESS
AND SHOWERS. ALTHOUGH SHOWER ACTIVITY HAS RECENTLY BECOME A LITTLE
LESS ORGANIZED...ENVIRONMENTAL CONDITIONS AND COMPUTER MODELS FAVOR
THE FORMATION OF A TROPICAL DEPRESSION DURING THE NEXT COUPLE OF
DAYS. THERE IS A HIGH CHANCE...90 PERCENT...OF THIS SYSTEM BECOMING
A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES
WEST-NORTHWESTWARD NEAR 15 MPH.

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TCFA Issued

2010082418
13.0 334.6
14.7 328.2
100
13.0 334.7
250100
1008250100
1
WTNT21 KNGU 250100
MSGID/GENADMIN/NAVMARFCSTCEN NORFOLK VA//
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/1. FORMATION OF A TROPICAL CYCLONE IS POSSIBLE WITHIN 100NM
EITHER SIDE OF A LINE FROM 13.0N 25.4W TO 14.7N 31.8W OVER THE
NEXT 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE OF A NUMBERED
TROPICAL CYCLONE WARNING AT THIS TIME.
2. A 1050 ZULU ASCAT PASS SOUTH OF THE CAPE VERDE ISLANDS
SHOWS AN ELONGATED AREA OF CYCLONIC CIRCULATION. CURRENT REGIONAL
MODELS ARE SHOWING INTENSIFICATION OF THIS LOW OVER THE
NEXT 24HRS. THIS, IN CONJUNCTION WITH WARM SEA SURFACE TEMPERATURES
OF 86 TO 88 DEGREES FAHRENHEIT SHOULD HELP TO ENHANCE THE DEVELOPMENT
OF THIS TROPICAL FEATURE.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO A WARNING OR ALLOWED TO
EXPIRE BY 260100Z AUG 2010.//

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Rob Lightbown:

Invest 96-L In The Far Eastern Atlantic:
I am also keeping close watch on a broad area of low pressure, designated Invest 96-L, located about 200 miles west-southwest of the southernmost Cape Verde Islands. Convection with this system continues to pulse up and down and satellite imagery shows an abundant amount of dry air to this system’s west. This will likely limit development for the next day or so, however, Invest 96-L is in an area of low shear and I suspect we will see development into a tropical depression by or before Friday.
The track model guidance forecasts a general west-northwest track for the next several days with a bend more to the northwest by early next week. Invest 96-L’s future track will highly depend on exactly where Danielle tracks and it is still unclear whether this system will follow Danielle out into the open Atlantic or will it sneak underneath and continue tracking west-northwest. There is plenty of time to monitor the progress of this system and I will keep you all updated.

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100%

tlantic Graphical TWO Area 1 closeup

Return to Atlantic Graphical TWO 1. A WELL-DEFINED LOW PRESSURE SYSTEM LOCATED ABOUT 300 MILES
WEST-SOUTHWEST OF THE SOUTHERNMOST CAPE VERDE ISLANDS IS MOVING
WESTWARD AT 15 MPH. THUNDERSTORM ACTIVITY HAS INCREASED AND IS NOW
MORE CONCENTRATED NEAR THE CENTER...AND A TROPICAL DEPRESSION
APPEARS TO BE DEVELOPING. ADVISORIES WILL LIKELY BE INITIATED ON
THIS DISTURBANCE LATER THIS MORNING. THERE IS A HIGH CHANCE...NEAR
100 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS

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BEGIN
NHC_ATCF
invest_RENUMBER_al962010_al072010.ren
FSTDA
R
U
040
010
0000
201008251224
NONE
NOTIFY=ATRP
END

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Dynamic:

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...

NEW TROPICAL DEPRESSION FORMS IN THE FAR EASTERN
ATLANTIC...EXPECTED TO BECOME A TROPICAL STORM LATER TODAY...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...14.3N 30.8W
ABOUT 430 MI...690 KM W OF THE SOUTHERNMOST CAPE VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/HR
PRESENT MOVEMENT...W OR 275 DEGREES AT 17 MPH...28 KM/HR
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES

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11AM

WTNT42 KNHC 251434
TCDAT2
TROPICAL DEPRESSION SEVEN DISCUSSION NUMBER 2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072010
1100 AM AST WED AUG 25 2010

THE AREA OF DISTURBED WEATHER THAT MOVED OFF THE WEST COAST OF
AFRICA TWO DAYS AGO AND PASSED SOUTH OF THE CAPE VERDE ISLANDS
YESTERDAY HAS BECOME BETTER ORGANIZED AND IS NOW TROPICAL
DEPRESSION SEVEN. THE DEPRESSION HAS A LARGE CYCLONIC ENVELOPE WITH
WELL-DEFINED CYCLONICALLY-CURVED CONVECTIVE BANDS...AND AN
ESTABLISHED UPPER-LEVEL OUTFLOW IN THE WESTERN SEMICIRCLE.
T-NUMBERS FROM BOTH TAFB AND SAB ARE 2.0...WITH DATA-T NUMBERS OF
2.5...ON THE DVORAK SCALE SUPPORT TROPICAL DEPRESSION STATUS AND
VERY CLOSE TO TROPICAL STORM INTENSITY. THE DEPRESSION WILL LIKELY
BECOME A TROPICAL STORM LATER TODAY AND THERE IS UNUSUALLY WARM
WATER OVER THE TROPICAL ATLANTIC...AND THE SHEAR IS FORECAST TO
REMAIN LOW FOR THE NEXT 2 TO 3 DAYS. THESE CONDITIONS WOULD FAVOR A
GRADUAL STRENGTHENING AND EVEN DESPITE THE SMALL INCREASE IN SHEAR
AT DAYS 4 AND 5...THE CONDITIONS ARE EXPECTED TO REMAIN FAVORABLE
FOR INTENSIFICATION. BOTH CLIMATOLOGY AND DYNAMICAL MODELS ARE ON
THE SIDE OF STRENGTHENING AND THE OFFICIAL FORECAST CALLS FOR THE
DEPRESSION TO BECOME A HURRICANE IN THREE DAYS OR SO.

THE DEPRESSION IS MOVING TOWARD THE WEST OR 275 DEGREES AT 15 KNOTS
TO THE SOUTH OF A SUBTROPICAL RIDGE. THIS GENERAL MOTION IS
EXPECTED TO CONTINUE DURING THE NEXT 2 TO 3 DAYS. THEREAFTER...THE
CYCLONE MOST LIKELY WILL DECREASE IN FORWARD SPEED AS IT REACHES A
WEAKNESS IN THE SUBTROPICAL RIDGE LEFT BY DANIELLE. BY THEN...THE
CYCLONE SHOULD BEGIN TO TURN TOWARD THE WEST-NORTHWEST. THE
OFFICIAL FORECAST IS BASICALLY IN THE MIDDLE OF THE TIGHTLY
CLUSTERED GUIDANCE ENVELOPE. MOST OF THE NUMERICAL GUIDANCE SHOWS A
PERSISTENT TROUGH OVER THE WESTERN ATLANTIC. IF THIS PATTERN
MATERIALIZES...IT WOULD STEER THE CYCLONE TOWARD THE NORTHWEST AWAY
FROM THE LESSER ANTILLES.



FORECAST POSITIONS AND MAX WINDS

INITIAL 25/1500Z 14.3N 30.8W 30 KT
12HR VT 26/0000Z 14.7N 33.7W 35 KT
24HR VT 26/1200Z 15.2N 36.5W 40 KT
36HR VT 27/0000Z 16.0N 39.5W 45 KT
48HR VT 27/1200Z 16.5N 42.5W 55 KT
72HR VT 28/1200Z 18.0N 48.5W 65 KT
96HR VT 29/1200Z 19.0N 53.5W 75 KT
120HR VT 30/1200Z 20.5N 57.0W 85 KT

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Jeff Masters

Posted by: JeffMasters, 3:15 PM GMT on August 25, 2010 Hurricane Danielle has changed little in organization over the past 12 hours, and is having trouble with strong upper level westerly winds that are creating a moderate 15 - 20 knots of wind shear. Latest satellite loops show that most of Danielle's low level spiral bands are on the east side of the storm, away from the shear. There is also a considerable amount of dry air on the west side of the storm that is inhibiting thunderstorm formation on the hurricane's west side. Danielle is over warm 28°C water. The Hurricane Hunters will begin flying missions into Danielle on Friday afternoon, since the storm is still too far from land to reach with their airplanes.


Figure 1. Morning satellite image of Danielle, Tropical Depression Seven, and a new tropical wave emerging from the coast of Africa (possibly to be designated 97L?)

Intensity forecast for Danielle
In the short term, now through Thursday, persistent wind shear of 15 - 20 knots due to strong upper level winds out of the west should keep any intensification of Danielle slow. The latest wind shear forecast from the SHIPS model calls for shear to fall to the low range, 5 - 10 knots, Friday through Saturday. With SSTs expected to be a warm 28 - 29°C, these conditions may favor a bout of rapid intensification. It is possible Danielle could become a major Category 3 hurricane by Saturday night and Sunday, when it should be making its closest approach to Bermuda.

Track forecast for Danielle
The trough of low pressure over the mid-Atlantic Ocean steering Danielle more to the northwest will wane in influence over the next two days, as a ridge of high pressure moves north of the storm. This will keep Danielle moving generally northwest towards Bermuda over the next three days. On Saturday, a new trough of low pressure that is expected to move off the East Coast of the U.S. and Canada should begin pulling Danielle due north, eventually recurving the storm out to sea without hitting land. However, one model--the NOGAPS--predicts that Danielle will be moving too slowly and that the new trough will not be strong enough to recurve Danielle out to sea. The NOGAPS keeps Danielle moving on a northwest course, passing very close to Bermuda, and coming perilously close the Northeast U.S. coast 7 - 8 days from now. The NOGAPS is an outlier in the models, and the official NHC forecast follows the consensus of our other reliable models, calling for Danielle to turn towards the north this weekend and miss Bermuda. These models include the three best-performing models from last year at making 4 - 5 day forecasts--the Canadian, ECMWF, and GFS models. Assuming Danielle follows the official NHC track, Bermuda can expect the storm's outer winds to reach the island Saturday night. NHC is giving Bermuda a 39% chance of receiving tropical storm force winds of 39 mph or greater from Danielle, and a 9% chance of getting hurricane force winds.

History suggests that a storm in Danielle's current location has only a 15% chance of making landfall on the U.S. East Coast. If Danielle passes east of Bermuda, as forecast, these percentages drop to less than 5%. However, Danielle will bring high surf conditions to the U.S. East Coast beginning this weekend. The latest wave forecast from NOAA's Wavewatch III model (which uses the GFS model as its prediction for the position and intensity of hurricanes), calls for waves from Danielle to begin hitting the coast of North Carolina on Saturday. These waves will build to 6 - 9 feet in the offshore waters from Northern Florida to North Carolina by Sunday. The latest nearshore water forecast for Cape Hatteras calls for 5 - 8 foot waves Saturday through Sunday. Waves will be much higher in Bermuda, where the Bermuda Weather Service is predicting 10 - 15 foot waves this weekend.


Figure 2. Wave forecast for the Atlantic made by NOAA's Wavewatch III model for Sunday morning, August 29, 2010. The model was run at 2am EDT Wednesday, August 25. The model is predicting that waves from Danielle of 2 - 3 meters (6 - 9 feet) will begin affecting the offshore waters from northern Florida to Cape Hatteras, North Carolina, on Sunday. These waves will cause considerable beach erosion and dangerous rip currents.

Tropical Depression Seven
Satellite images show that the tropical wave (96L) that emerged off the coast of Africa Monday has become Tropical Depression Seven. Satellite estimates of TD 7's strength support calling this a 35 mph tropical depression, and latest satellite loops show a well-organized system with an increasing amount of heavy thunderstorm activity, plenty of low-level spiral banding, and expanding upper-level outflow to the north. This is likely to be Tropical Storm Earl later today. Tropical Depression Seven is now well east of the Cape Verdes Islands, and has a large stretch of open ocean before it. Water vapor satellite images show a large region of dry air from the Sahara lies to the west of TD 7, and this dry air will likely be the primary inhibiting factor for development over the next three days. Wind shear is low, 5 - 10 knots, and sea surface temperatures are warm, around 28°C.

Forecast for Tropical Depression Seven
Wind shear is predicted to remain low, 5 - 10 knots, for the next three days. SSTs will cool a bit to 27.5°C by Thursday, but this is still above the 26.5°C threshold for hurricane development. TD 7 may cross Danielle's cold water wake at some point, which may interrupt development. Dry air will probably be the main inhibiting factor for TD 7 over the next three days. The SHIPS model is indicating an increase in wind shear to the moderate range, 10 - 20 knots, 4 - 5 days from now. In combination, these factors should allow for a slow intensification of TD 7 into Hurricane Earl 4 -5 days from now.

The long range fate of TD 7 remains unclear. The storm is being steering by the same ridge of high pressure steering Danielle, and will initially follow a track similar to Danielle. As TD 7 approaches the central Atlantic 4 - 6 days from now, the storm will encounter the same mid-Atlantic trough that is expected to turn Danielle to the north. This trough should be able to turn TD 7 far enough to the northwest so that it will miss the Lesser Antilles Islands. However, it is unclear at this point whether this trough will be strong enough to fully recurve TD 7 out to sea, east of Bermuda. This will, in part, depend upon how strong Danielle gets and how fast it moves. A stronger Danielle is likely to create more of a break in the ridge of high pressure steering TD 7, encouraging the storm to turn north and recurve out to sea. A weaker Danielle will make TD 7 more likely to miss recurvature, and follow a track to the west or west-northwest towards the U.S. East Coast early next week. History suggests that a storm in TD 7's current location has only a 20% chance of making landfall on the U.S. East Coast.

Elsewhere in the Tropics
A new tropical wave is emerging from the coast of Africa this morning (Figure 1.) The latest GFS model run develops this wave into a tropical depression 3 - 4 days from now. I can't see any reason why this would not occur. Conditions for tropical cyclone development will remain favorable in the Eastern Atlantic for at least the next week, and the GFS models has successfully predicted the development of both Danielle and TD 7 over the past two weeks. This new wave probably has a better chance of hitting the U.S. East Coast than either Danielle or TD 7.

Over in the Gulf of Mexico, a trough of low pressure is generating some disorganized thunderstorm activity. This action may increase on Thursday and Friday, when a cold front is expected to move off the coast of Texas and over the Gulf. NHC is giving a 10% chance of this area of disturbed weather developing into a tropical depression by Friday. Any storm that might develop over the Gulf of Mexico from this disturbance would likely not stay over water long enough to develop into a hurricane, and none of the computer models currently support tropical cyclone development in the Gulf over the next seven days.

In the Eastern Pacific, Tropical Storm Frank has moved away the coast far enough from the Mexican coast to no longer pose a heavy rainfall threat, and all tropical storm warnings have been dropped.

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