Tropical Depression Two forms from Invest 98L

By: Dr. Jeff Masters , 9:33 PM GMT on July 17, 2011

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Tropical Depression Two (TD2) formed from Invest 98L this afternoon. Hurricane Hunters flew into the suspect area and found a surface circulation north of the Bahamas, with maximum sustained winds of 35 mph. They also determined the system had become warm core—a characteristic that must be present in order to declare a tropical cyclone. Satellite imagery continues to show the system is becoming more organized with a stronger circulation. Wind shear is forecast to remain favorable for the system until Tuesday or Wednesday when higher shear will slide in from the north. Sea surface temperatures are warm enough to sustain a tropical storm.


Figure 1. Satellite imagery of Tropical Depression Two in the Atlantic, east of Florida. This graphic will update to the current satellite imagery.


Figure 2. Official 5-day forecast for Tropical Depression Two. This graphic will remain current.

Forecast for TD2

The models are coming into better agreement as TD2 has become more organized. In terms of dynamical forecast models, the HWRF and GFS both forecast TD2 to max out just above tropical storm strenth. HWRF intensifies TD2 to around 47 mph in the next 24 hours, whereas GFS is a bit slower to bring the system up to tropical storm status. Two statistical models, the DSHP (SHIPS model that includes land interaction) and the LGEM (Logistical Growth Equation Model) both intensify TD2 to a moderate tropical storm over the next 2-3 days.

There tends to be a lot of uncertainty involved with tropical cyclones that form under these circumstances, but our forecast remains in line with the National Hurricane Center and the reliable forecast models. TD2 will move slowly to the northeast in weak steering currents over the next few days before eventually becoming an extratropical storm. There is minimal chance that this system will cross over Florida into the Gulf of Mexico. Timing and path depend heavily on how intense the cyclone gets, as Jeff mentioned in his blog earlier today. A weaker storm will tend to stay south, whereas a stronger storm will grow taller in the atmosphere and winds at higher levels will influence it and steer it northeast.

None of the reliable models predict tropical cyclone development over the remainder of the Atlantic through July 23.

Angela

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Another ob of TS winds uncontaminated..
43.8 knots (~ 50.4 mph)
Tropical Storm
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AMZ080-180330-
SW N ATLANTIC S OF 31N W OF 65W INCLUDING BAHAMAS
530 PM EDT SUN JUL 17 2011

...TROPICAL STORM WARNING FROM 26N TO 30N BETWEEN 76W AND 80W...

.TONIGHT AND MON...WITHIN 60 NM OF TROPICAL DEPRESSION TWO WINDS
25 TO 30 KT BECOMING TROPICAL STORM FORCE WINDS TONIGHT AND MON.
HIGHEST WINDS 45 KT GUSTS 55 KT. SEAS 8 TO 10 FT BUILDING TO 15
FT WITH SEAS 12 FT OR GREATER WITHIN AREA OF TROPICAL STORM
FORCE WINDS LATE TONIGHT AND MON. ELSEWHERE N OF 26N W OF 76W N
TO NE WINDS 15 TO 20 KT. SEAS 5 TO 8 FT. N OF 26N E OF 76W SE TO
S WINDS 10 TO 15 KT. SEAS 5 TO 7 FT. S OF 26N W OF 76W SE WINDS
5 TO 10 KT. SEAS 1 TO 2 FT. S OF 26N E OF 76W E TO SE WINDS 10
TO 15 KT EXCEPT 15 TO 20 KT S OF 22N E OF 74W. SEAS 4 TO 7 FT
EXCEPT 3 TO 5 FT W OF BAHAMAS.
.MON NIGHT THROUGH WED...TROPICAL STORM FORCE WINDS WITHIN 90 NM
OF CENTER. HIGHEST WINDS 50 KT GUSTS 60 KT. SEAS 12 FT OR
GREATER IN AREA OF TROPICAL STORM FORCE WINDS. HIGHEST SEAS 20
FT. ELSEWHERE WITHIN 150 NM OF TROPICAL STORM TWO WINDS 20 TO 30
KT. SEAS 8 TO 12 FT. ELSEWHERE N OF 27N W OF 77W NW TO N WINDS
10 TO 15 KT. SEAS 4 TO 7 FT. ELSEWHERE N OF 27N W OF 77W S TO
SW WINDS 15 TO 20 KT. SEAS 5 TO 8 FT. S OF 22N E OF 74W E TO SE
WINDS 15 TO 20 KT. SEAS 4 TO 7 FT. REMAINDER AREA SE WINDS 10
KT. SEAS 4 TO 6 FT EXCEPT 1 TO 3 FT W OF BAHAMAS.
.THU AND FRI...N OF 27N SW WINDS 10 TO 15 KT...EXCEPT 5 TO 10 KT
E OF 60W. SEAS 2 TO 4 FT. FROM 25N TO 27N SE TO S WINDS 5 TO 10
KT. SEAS 3 TO 4 FT...EXCEPT 1 TO 2 FT W OF BAHAMAS. FROM 23N TO
25N SE TO E WINDS 10 TO 15 KT. SEAS 4 TO 5 FT...EXCEPT 2 TO 3 FT
W OF BAHAMAS. S OF 23N E TO SE WINDS 10 TO 15 KT INCREASING TO
15 TO 20 KT FRI. SEAS 4 TO 6 FT INCREASING TO 5 TO 8 FT...EXCEPT
3 TO 5 FT W OF BAHAMAS.

$$
FORECASTER SCHAUER
Member Since: Posts: Comments:
Quoting Hurricanes101:
TD2 will continue to move slowly to the northeast in weak steering currents over the next few days before eventually becoming an extratropical storm

Continue? That would imply it is moving NE now; which it is not


Exactly. It's moving south, no where near NE. Sorry Angela, but it's not gonna move NE for quite a while.
Member Since: October 8, 2008 Posts: 14 Comments: 4553
21. angelafritz (Admin)
Yes you're right, that was poor wording! Changing now. :)

Quoting Stormchaser2007:



It's actually moving SE according to recon.
Thanks Angela!
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Expect significant track changes with this storm. If they never had a handle on it doing what it's done, why would we listen to their track off to the NE...they're step behind looks like and ridge is gonna be the silent key to this storm
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Thanks for the timely update here Angela, good job!
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Quoting Randyman:
OK...last time I checked it was at 40%...cool



40% on what?
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Woah... now, that was unexpected....
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Member Since: July 3, 2005 Posts: 426 Comments: 129093
None of the reliable models predict tropical cyclone development over the remainder of the Atlantic through July 23.

I really think the Doc needs to leave this statement from his blog. Models? What models? are you kidding me

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12. 7544
hmmmm intersting post thanks

There is minimal chance that this system will cross over Florida into the Gulf of Mexico.
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Thanks Angela :)
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Quoting Hurricanes101:
TD2 will continue to move slowly to the northeast in weak steering currents over the next few days before eventually becoming an extratropical storm

Continue? That would imply it is moving NE now; which it is not



It's actually moving SE according to recon.
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Quoting taco2me61:
Thanks Dr Masters for the Up-date....
It does look like we have Tropical Storm Bret Now

Taco :o)


No thank Angela, not Dr. M
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TD2 will continue to move slowly to the northeast in weak steering currents over the next few days before eventually becoming an extratropical storm

Continue? That would imply it is moving NE now; which it is not
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OK...last time I checked it was at 40%...cool
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Thanks Dr Masters for the Up-date....
It does look like we have Tropical Storm Bret Now

Taco :o)
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thanks doc


hope you are having a good sunday evening

funny how fast things change
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Interesting as always to watch as the season goes off to the races. Thank you, Angela...
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Whoa Link
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.