98L may develop into a tropical depression near Florida; Ma-on a threat to Japan

By: Dr. Jeff Masters , 3:09 PM GMT on July 17, 2011

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A tropical disturbance (Invest 98L) has formed off the east coast of Florida, along the tail end of a cold front that pushed off the coast late last week. This disturbance has the potential to develop into a tropical depression that will bring heavy rains to the northern Bahamas and east coast of Florida today through Tuesday. Satellite imagery shows that the disturbance has become more organized this morning, with an expanding area of intense thunderstorms, the beginnings of a surface circulation, and upper-level outflow on the east and north sides of the storm. Some rotation of 98L is also evident on long-range radar out of Melbourne, Florida, but the rain showers are poorly organized and there is little evidence of low-level spiral banding. Wind shear is a moderate 10 - 20 knots, and sea surface temperatures are 27 - 28°C, which is plenty warm enough to support a tropical storm. There is dry, continental air over North Florida, and upper level winds out of the northwest are driving this dry air into the center of 98L, retarding development.


Figure 1. Morning satellite image of Invest 98L.

Forecast for 98L
The models are shy about developing 98L; only the HWRF model shows a tropical depression developing. The SHIPS model predicts that wind shear will be in the low to moderate range, 5 - 15 knots, over the next five days. NHC is giving 98L a 30% chance of developing into a tropical depression by Wednesday. Given the recent satellite and radar presentation of the storm, I'd put those odds higher, at 50%. A hurricane hunter aircraft is scheduled to investigate 98L this afternoon.

Steering currents are weak off the coast of Florida, and 98L can be expected to move slowly at less than 5 mph over the next two days. The HWRF and GFDL models predict 98L will execute a clockwise loop, heading towards the coast of Florida on Monday, then looping northeastwards towards South Carolina later in the week. The track of 98L will depend strongly on how intense the storm gets; a weak system is likely to stay farther to the south, while a stronger system will "feel" upper level winds with a west-to-east component, and tend to move to the northeast, parallel to the coast.

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

U.S. heat wave to last at least another week
An unusually intense, widespread, and long-lasting heat wave over the majority of the U.S. continues to set numerous daily record highs. The latest long-range forecasts from the GFS and ECMWF models predict that the ridge of high pressure responsible for the heat wave will remain entrenched over the center or eastern portion of the country during the coming week, so the heat wave should continue for all but the Pacific Northwest through July 23. The GFS model does show that the ridge will break down some during the period 10 - 16 days from now, but such long range forecasts have low skill, and the heat wave could easily continue through the remainder of July. I'll present a more detailed look at the heat wave later this week.


Figure 2. Microwave satellite image of Typhoon Ma-on at 08:26 UTC July 17, 2011, over the West Pacific Ocean. The typhoon was undergoing an eyewall replacement cycle, with the inner eyewall collapsing and a new, larger eyewall forming from an outer spiral band. Image credit: Navy Research Lab, Monterey.

Typhoon Ma-on headed towards Japan
Powerful Category 3 Typhoon Ma-on is headed northwestward towards Japan, and is expected to brush the east coast of the main island of Honshu on Tuesday. The typhoon has weakened some over the past day, thanks to an eyewall replacement cycle where the inner eyewall collapsed, and a new, larger eyewall formed from an outer spiral band. Once this process completes, Ma-on is expected to intensify into a Category 4 storm. With water temperatures along the path of the typhoon ranging from 29 - 30°C, and wind shear expected to remain in the low to moderate range of 5 - 15 knots, Ma-on has the potential to hit Japan as a major Category 3 storm. The typhoon is unusually large, with winds of tropical storm force (39+ mph) extending out almost 350 miles to the north of the storm. A large portion of the south coast of Japan will receive tropical storm-force winds and large battering waves from Ma-on. Although the typhoon is currently a minimal Category 3 storm, its large size means that Ma-on has a tremendous amount of total kinetic energy, characteristic of a Category 5 storm. This means that Ma-on has the potential to bring a large and highly destructive storm to the coast on the right front side of where the eye makes landfall. If the eye remains just offshore, as some models are predicting, this storm surge will largely miss Japan, though.

Jeff Masters

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652. ackee
INTRESTING times ahead what will the NHC do according to recon we have a TD but 98L still look poorly organize to me what will the NHC do at 5pm only time will tell
Member Since: July 15, 2008 Posts: 0 Comments: 1346
C'mon...it looks like a duck, smells like a duck.....throw some orange sauce on it and serve it already. And bring out those 20 plates of crow.
Member Since: November 7, 2009 Posts: 0 Comments: 23
Quoting Hurrykane:
Subtropical?


Not at all. Temperature profile in system as well as satellite intensity estimates all support a fully tropical entity.
Member Since: April 14, 2007 Posts: 8 Comments: 5163
...just opened a cold "FRESCA"
Member Since: July 3, 2005 Posts: 421 Comments: 127559
The circulation looks to be moving east, being pushed by the dry airmass to the NW
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Quoting Hurrykane:
Subtropical?

I thought this was a warm core low
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Quoting NICycloneChaser:


No conformation of a closed circulation, never mind a well-defined one. I really don't think this is a TD quite yet.


Scrap that, just refreshed the recon data. Looking like a fairly decent circulation, that's where lowest pressure is too. Not far off.
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Now we are seeing lower pressures
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So much for the theory of an ill-defined surface low...

Tight circulation with max winds near 40-45mph. Very nice circulation with 25knts on both N/S ends.

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the hardest winds to get are usually West winds therefore if we have west winds we likely have a closed low... not saying we do without a doubt but probably 95% sure it is closed... also winds are at least 30 knts could go with 35 knts since it is so close to land
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Quoting Hurrykane:
Subtropical?


No, this is fully tropical as the max winds were near the center.
Member Since: July 8, 2005 Posts: 259 Comments: 23571
Real-Time Twitter Posts
severestudios: Tornado damage has been reported near New Rockford, ND. Roger Hill reported another tornado near Juanita about 40 min. ago. #ndwx
Member Since: May 17, 2009 Posts: 2 Comments: 904
640. 7544
Quoting cchsweatherman:
Based upon Hurricane Hunter recon data, I strongly believe that we have at the very least Tropical Depression 2 and could possibly have Tropical Storm Bret.


agree agree but where you think it might track thanks
Member Since: May 6, 2007 Posts: 0 Comments: 6690
Quoting HurricaneDean07:
"Houston"
We have westerly winds... appears closed on the north and SW side, just need SE side checked...


Copy That will be heading that way on our next "Pass"

Taco :o)
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638. ackee
Quoting xcool:


storm in gom
saw that guess the tropics will begin to heat up
Member Since: July 15, 2008 Posts: 0 Comments: 1346
Quoting Levi32:
Westerly winds reported with 1010mb pressure. This very well may be a tropical depression.


Exactly what I was expecting.
Member Since: April 14, 2007 Posts: 8 Comments: 5163
Quoting Thundercloud01221991:
west winds with pressure of 1010 mb

we have a depression according to recon


No conformation of a closed circulation, never mind a well-defined one. I really don't think this is a TD quite yet.
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Been watching the atcf ftp site for a renumber, I suspect that might very well be coming depending on the SE side of the system.
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Getting W winds now too, that 1010 mb was likely the center.
Member Since: July 8, 2005 Posts: 259 Comments: 23571
Quoting allstar:
Those are rain flagged, which mean they arent accurate...

Status:
35 to 40 mph ; 1010 MB
(Checking for closed low, NW,NE,SW all checked... Need SE)
Member Since: October 3, 2010 Posts: 40 Comments: 4129
Westerly winds reported with 1010mb pressure. This very well may be a tropical depression.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
Based upon Hurricane Hunter recon data, I strongly believe that we have at the very least Tropical Depression 2 and could possibly have Tropical Storm Bret.
Member Since: April 14, 2007 Posts: 8 Comments: 5163
627. beell
WV 98L Floater
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Quoting AllStar17:
Tropical storm force winds being observed along with the 1010 mb pressures.


I agree with this statment :o)

Taco :o)
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On the SFMR.
35 knots
(~ 40.2 mph)
Member Since: July 8, 2005 Posts: 259 Comments: 23571
Flight level winds support TS.
44 knots
(~ 50.6 mph)
Member Since: July 8, 2005 Posts: 259 Comments: 23571


IR w/ Low Level Winds - North Atlantic - Latest Available
Member Since: July 3, 2005 Posts: 421 Comments: 127559
Time: 19:29:00Z
Coordinates: 27.5833N 78.2667W
Acft. Static Air Press: 990.2 mb (~ 29.24 inHg)
Acft. Geopotential Hgt: 172 meters (~ 564 feet)
Extrap. Sfc. Press: 1010.0 mb (~ 29.83 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 264° at 21 knots (From the W at ~ 24.1 mph)
Air Temp: 22.8°C (~ 73.0°F)
Dew Pt: 19.1°C (~ 66.4°F)
Peak (10s) Flt. Lvl. Wind: 27 knots (~ 31.0 mph)
SFMR Peak (10s) Sfc. Wind: 27 knots (~ 31.0 mph)
SFMR Rain Rate: 5 mm/hr (~ 0.20 in/hr)
(*) Denotes suspect data
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1010.0 mb
(~ 29.83 inHg)
Member Since: July 8, 2005 Posts: 259 Comments: 23571
no surface winds indicate TS winds quite yet, but a Tstorm that recon just went through has 45 to 50 MPH, but its rain flagged so... nothin yet.
Member Since: October 3, 2010 Posts: 40 Comments: 4129
Quoting HurricaneDean07:
Good, if you come to Texas anytime soon, bring that rain with you please, and thank you... actually got to see rain on the windshield of the car when i was on my vacation(New Mexico/Colorado). those monsoonal showers come in handy over there.


When I head to Houston I will bring it with me thats for sure....I do understand that you all need it worse than we do....

Taco :o)
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Time: 19:26:30Z
Coordinates: 27.6833N 78.3333W
Acft. Static Air Press: 990.3 mb (~ 29.24 inHg)
Acft. Geopotential Hgt: 189 meters (~ 620 feet)
Extrap. Sfc. Press: 1012.1 mb (~ 29.89 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 45° at 43 knots (From the NE at ~ 49.4 mph)
Air Temp: 20.7°C (~ 69.3°F)
Dew Pt: 18.2°C (~ 64.8°F)
Peak (10s) Flt. Lvl. Wind: 44 knots (~ 50.6 mph)
SFMR Peak (10s) Sfc. Wind: 43 knots* (~ 49.4 mph*)
SFMR Rain Rate: 4 mm/hr* (~ 0.16 in/hr*)

I think that's a little too far...
Member Since: April 23, 2011 Posts: 104 Comments: 14871
616. Skyepony (Mod)
Solid west wind over 30kts around 600'....
Member Since: August 10, 2005 Posts: 161 Comments: 37353
"Houston"
We have westerly winds... appears closed on the north and SW side, just need SE side checked...
Member Since: October 3, 2010 Posts: 40 Comments: 4129
Quoting KEEPEROFTHEGATE:
SOMETHING HAS LEFT AFRICA OVER WATER NOW KEEP WATCH

Wow Wow
Member Since: October 28, 2010 Posts: 0 Comments: 65
Time: 19:30:30Z
Coordinates: 27.5333N 78.25W
Acft. Static Air Press: 990.8 mb (~ 29.26 inHg)
Acft. Geopotential Hgt: 178 meters (~ 584 feet)
Extrap. Sfc. Press: 1011.5 mb (~ 29.87 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 256° at 32 knots (From the WSW at ~ 36.8 mph)
Air Temp: 22.5°C (~ 72.5°F)
Dew Pt: 19.8°C (~ 67.6°F)
Peak (10s) Flt. Lvl. Wind: 33 knots (~ 37.9 mph)
SFMR Peak (10s) Sfc. Wind: 35 knots (~ 40.2 mph)
SFMR Rain Rate: 1 mm/hr (~ 0.04 in/hr)

look at the pressure , it',s closed I suspect they go straight to TS Bret.
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That was the trend, (down in mb) as the sat Improves on viz ,the pressure falls a tad later and has during this teal Flight,,so their timing was fortunate.

Dvorak

Member Since: July 3, 2005 Posts: 421 Comments: 127559
Quoting KEEPEROFTHEGATE:
SOMETHING HAS LEFT AFRICA OVER WATER NOW KEEP WATCH

That wave is one of the largest one's I have ever seen!!
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Oh hi TD 2/Bret nice to meet you.
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Quoting Levi32:


Most of the spin you see is mid-level. There is some circulation at the surface, but it is not that strong at all.


Levi, how does one distinguish between midlevel and surface circulation on the sat loops?
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608. xcool


storm in gom
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Tropical storm force winds being observed along with the 1010 mb pressures.
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Thanks Keeper, waiting for the rename.

Reason for being conservative is that when they pull the named storm alarm, it creates all types of responses from local authorities. All of this causes lots of money to be spent. AND if nothing happens, it makes it tough to believe them and people get complacent. I don't know if you have been paying attention, but these are not the best of times for money in government...

Even if 98L was a TS, at this point, the cone of terror wouldn't be over land, going by the current model runs, but I guarantee you will have some nervous people out there.

Having said that, I agree that they seem to be a little too conservative at times, but I understand why.
Member Since: March 10, 2006 Posts: 0 Comments: 10034
west winds with pressure of 1010 mb

we have a depression according to recon
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Quoting nrtiwlnvragn:
Recent data may indicate a TD, flight level winds at least higher than SFMR and 1010 mb.


Very much agreed and expected.
Member Since: April 14, 2007 Posts: 8 Comments: 5163
Flight level winds of 43 knots on the east side.
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602. Skyepony (Mod)
There it is recon found 1010mb, solid west wind, for a moment.. COC ~27.583N 78.267W
Member Since: August 10, 2005 Posts: 161 Comments: 37353

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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.

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