Tropical Storm Danny not impressive yet
Tropical Storm Danny is here, born from an African tropical wave that developed a closed circulation and some respectable heavy thunderstorm activity this morning. Data between 2 - 3 pm EDT from the Hurricane Hunters indicates the Danny has a central pressure of 1009 mb, and top surface winds of about 45 mph. Satellite imagery shows that Danny's circulation has gotten stretched and pulled away from the heaviest thunderstorm activity on the storm's east side. It is possible that Danny's center will reform at a different location, closer to the heaviest thunderstorms, so the model forecasts probably have a higher degree of uncertainty than usual at present. Wind shear has dropped to the low range, 5 - 10 knots. The upper-level low Danny is moving underneath has plenty of dry air in it, and this dry air is intruding into Danny's west side, keeping and heavy thunderstorm activity from developing on that side.
Figure 1. Oceanic heat content for August 25, 2009. Regions where the Sea Surface Temperature is below 80°F, or where the shallow waters of the Continental Shelf lie, do not have enough heat content to be plotted, and are shown in white colors. The oceanic heat content along the track of Tropical Storm Danny is below the threshold of 90 kJ/cm^2 typically seen with cases of rapid intensification. The storm position at 8am EDT today is given by the hurricane symbol with the "0" inside it. Subsequent hurricane symbols show the official NHC forecast points from the 11 am EDT forecast today, for 8am Thursday (24 hours), 8am Friday (48 hours), 8am Saturday (72 hours), and 8am Sunday (72 hours). The cold waters stirred up by Hurricane Bill last week will not impact Tropical Storm Danny. Image credit: RSMAS, University of Miami.
The forecast for Danny
As Danny continues to plow through the upper low, the low will weaken, but will dump dry air into the storm through Thursday afternoon, slowing down development. By Thursday night, when Danny should be several hundred miles off the coast of northern Florida, the upper-level low may be weak enough and far enough away that Danny will find itself in a region with light upper level anticyclonic winds, which would favor more rapid development. Ocean heat content (Figure 1) is high enough to support a hurricane, until Danny gets to about New Jersey's latitude. Most of the intensity models, including the GFDL, HWRF, and SHIPS model, forecast that Danny will become a hurricane by Friday. However, this favorable environment will not last long, since a strong trough of low pressure will be approaching the U.S. East Coast on Friday. This trough will bring high wind shear of 20 - 30 knots by Friday night. This trough should be strong enough to turn Danny to the north, then northeast on Saturday. The models have come into better agreement keeping Danny offshore as it passes North Carolina, though the storm is certainly capable of giving the Outer Banks a direct hit. As Danny passes North Carolina, it should start heading north-northeast, with a landfall likely Saturday afternoon or evening somewhere between Massachusetts and Nova Scotia. At that time, Danny is likely to be a strong tropical storm or weak Category 1 hurricane, with winds in the 55 - 80 mph range. The latest runs of the GFDL and GFS model have Danny tracking directly over Martha's Vineyard, where President Obama is on vacation. It will be interesting to see if the president stays on the island for Danny.
For those of you wondering about specific probabilities of getting tropical storm force or hurricane force winds, consult the NHC Wind Probability Product.
Figure 2. Tropical wave newly emerged from the coast of Africa, with some potential for development.
Elsewhere in the Atlantic
A well-organized tropical wave has exited the coast of Africa, and lies a few hundred miles southeast of the Cape Verdes Islands. None of the models are gung-ho about developing this wave, but shear is low, 10 knots, and waters are warm enough to support development. The dry Saharan Air Layer is relatively limited in extent and intensity, so dry air may have only a small inhibiting effect on the wave. Expect some slow development of this wave as it moves westward over the next few days. NHC is giving this system a low (less than 30% chance) of developing into a tropical depression by Friday afternoon.
I'll have an update Thursday.
Jeff Masters
Reader Comments
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 — Blog Index
Glad you were able to make that trip worthwhile. Can't wait to see footage. I haven't looked at the Key West footage yet. How did the NWS footage turn out?
Reflector site for those at work, which includes Weather456, daily update.
AOI
AOI
AOI
AOI
The storms ability to organize is being disrupted by it's surrounding environment.
They also had to shift the centre to the NNE when they first got out there.. and even then.. its not much of a system.
i have always known plus the doctor has told me that my right eye is my good one so i'll compromise and keep my good eye on 94L and my left eye on Danny
sorry thats the best i can do as the other way around would be difficult
The NWS footage is awesome...like everything else!
Hey Junky! How about those frames I pulled from my video? Pretty cool, huh! Man, I busted my butt over there on that island nation! :)
Looking forward to receiving your DVD. Very important footage for the late winter series we're producing!
Oz---
The pattern potentially taking shape is one that would increase the risk to the Caribbean, SE coast & GOM. Troughing has been the recurring dominant feature so I am a little skeptical of the ridging building in and breaking the current pattern. I'll believe it when I see it, basically, stay tuned.
Steering flow for a weak naked swirl is WNW.
If you notice, the forecasts are normally based on 48 hour increments. It does not say that after 48 hours it could have a better chance of developing further. The experts have long ago decided on a more cautious approach, lest people panic too quickly and when a systems fizzles, people have a tendency to become complacent. Years ago the airports would close 2 to 3 days before an approaching storm; only to have the systems move away. They no longer do that. They declare an invest when a system has enough potential to become a threat. I hope this answer helps.
Looks like someone has faith in 94L
This one has a current track that is very disconcerting....and it looks like it wants to become a buzz-saw.
definitely was a tropical storm at one point, and if this data is complete it is a big change from what they found the last couple times out. Wouldn't go critical on the NHC, they were correct for upgrading the storm. I would say this storm has been in a flip flop between sub-tropical and tropical the entire time, but imagine how much confusion it would cause if the NHC kept changing the classification? Plus computer models react different once you classify a storm as tropical or change it to sub-tropical/non-tropical. That is part of the importance of correctly classifying a storm once it IS tropical, or something close to it - because these kinds of changes are progged into the models and has an, at times, dramatic effect on their predictions.
That NOAA plane was flying at a much higher altitude (10,000-12,500 ft) than the USAF planes (1,500 ft) that have recently flown the system. Since it is not a well developed cyclone its winds don't extend upwards as high. However, if it has weakened we should see when the 18Z USAF plane flys.
Very cool photo OZ
Great lightning pic! So far I really like what you're turning out. The Experience Bill video should be a treat. Keep us posted!
More like a cat1.
we've noticed, all should keep a close eye on this trend - but it probably can not be determined yet if it is indicative of a longer term westerly track
And it looks like it's coming off the coast of Africa moving WSW. I wonder how far down it'll go...
agreed with Cat 1, for the meantime. It's kind of different though once you talk about New England. This area is extremely poorly prepared for even Cat 1 winds if they are sustained. And because of tons of excessive rainfall this year, and the last few years being flood years on rivers such as the Housatonic... many once-were dirt levies no longer exist and at the same time river levels, water table levels, and pretty much everything that has to do with moisture/water in general are way above normal. So if this thing were to strike, say... the middle of Long Island, it would only need to be a minimal tropical storm to cause hurricane like damage in terms of flooding... and it would only need to be a strong Cat 1 to cause Cat 2 like damage to property, and possibly more in terms of trees/power lines. Many homes up here are built to sustain nothing more than 90MPH winds. This is why up here when an F0 or F1 tornado hits, homes are destroyed as if it were an F3 (but the tornadoes up here are usually never bigger than a tenth of a mile wide, so wide spread damage from them is rare). That in itself is a good example of how poorly prepared this area really is for a wide spread hurricane force wind event. Also, a lot of hills so a lot of higher-elevation wind enhancement possible. I honestly believe if a large Cat 2 storm were to strike, somewhere like in my example the middle of Long Island and cut through CT - the damage would look more like a Cat 3 or 4. We have not had a Hurricane come up through in that way in decades. People bring up Hurricane Gloria, but honestly Gloria was only bad for the southeastern part of New England. I was little and living in Danbury at the time, which is only 60 or so miles west of where Gloria passed through and all we got was a 1 hour thunderstorm and the rest of the night was partly cloudy. I worry about this, because people think Gloria was a good example of the possible impacts when in reality it was a big "let down" for most of this area. The damage was great where it was greatest, but almost none existent elsewhere.
while i agree with you right now, these type of statements could prove to be bad ha
i certainly don't agree with that. Dust devils don't have large areas of convection accompanying them ;) well I guess they CAN... but I see them more on sunny dry days. Of course, I am only being a kidder, I didn't really take this THAT literally.
edit - sorry, quoted the wrong person... meh ya'll know what i meant
haha good call :)
2009 Storms
Active
Atlantic
94L.INVEST
05L.DANNY
East Pacific
12E.IGNACIO
Central Pacific
95C.INVEST
11E.HILDA
West Pacific
98W.INVEST
91W.INVEST
90W.INVEST
Indian Ocean
Southern Hemisphere
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1253 UTC THU AUG 27 2009
DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.
ATLANTIC OBJECTIVE AIDS FOR
DISTURBANCE INVEST (AL942009) 20090827 1200 UTC
...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
090827 1200 090828 0000 090828 1200 090829 0000
LAT LON LAT LON LAT LON LAT LON
BAMS 10.5N 25.6W 11.3N 28.3W 12.1N 31.2W 12.9N 34.4W
BAMD 10.5N 25.6W 10.7N 28.1W 11.0N 30.6W 11.4N 33.0W
BAMM 10.5N 25.6W 11.0N 28.4W 11.3N 31.3W 11.6N 34.1W
LBAR 10.5N 25.6W 10.8N 28.6W 11.4N 31.9W 12.0N 35.4W
SHIP 25KTS 29KTS 36KTS 47KTS
DSHP 25KTS 29KTS 36KTS 47KTS
...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
090829 1200 090830 1200 090831 1200 090901 1200
LAT LON LAT LON LAT LON LAT LON
BAMS 13.3N 37.9W 13.4N 45.6W 13.3N 52.5W 13.4N 58.2W
BAMD 12.0N 35.3W 13.1N 39.0W 13.8N 41.8W 15.1N 44.1W
BAMM 12.0N 36.7W 12.8N 41.6W 12.9N 45.6W 12.7N 48.2W
LBAR 12.5N 38.9W 13.6N 45.3W 13.2N 44.6W 13.7N 46.3W
SHIP 58KTS 74KTS 76KTS 81KTS
DSHP 58KTS 74KTS 76KTS 81KTS
...INITIAL CONDITIONS...
LATCUR = 10.5N LONCUR = 25.6W DIRCUR = 270DEG SPDCUR = 15KT
LATM12 = 10.9N LONM12 = 22.6W DIRM12 = 263DEG SPDM12 = 15KT
LATM24 = 11.4N LONM24 = 19.5W
WNDCUR = 25KT RMAXWD = 0NM WNDM12 = 25KT
CENPRS = 1009MB OUTPRS = 1011MB OUTRAD = 200NM SDEPTH = D
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM
$$
NNNN
Just looked at the visible with the tracking points and I certainly agree with you! Looks to be going almost due West with very little movement to the North currently.
Due west movement, if any. The COC is slowing down to try and allow the convection to move over. And the official forecast points START going NNW, but its drifting west... honestly they must not have eyes.
Viewing: 1301 - 1351
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 — Blog Index