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
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Man, I just get done with work and off goes Myspace, Facebook, Twitter and this blog...you would think it was Armageddon...Danny looks sad...
don't be too sad...you missed my moronic nonsense on here earlier...and many a blogger would gladly trade places with you on that one...
I hear ya...hate driving in that mess. We have a mess coming down across S. LA. Yuck!
Seen it with my own eye's. Just reported on radio at Pine Island & Burnt Store.
They did comment that there was some debate about TS vs STS before they named it.
You spotted it this AM - good call.
You mean the old pic thing with the measurements??? I lurked on that...
How could it hit VA but not NC?
nope I spotted it yesterday xD
Landfall.
It's clear enough on the visible loop. Perhaps you're looking at the mass of cloud? Danny is the near naked swirl just to the west of that.
Tropical storms endure over wet land, fizzle over dry
WEST LAFAYETTE, Ind. - If it has already rained, it's going to continue to pour, according to a Purdue University study of how ocean-origin storms behave when they come ashore.
More than 30 years of monsoon data from India showed that ground moisture where the storms make landfall is a major indicator of what the storm will do from there. If the ground is wet, the storm is likely to sustain, while dry conditions should calm the storm.
"Once a storm comes overland, it was unclear whether it would stall, accelerate or fizzle out," said Dev Niyogi, Indiana state climatologist and associate professor of agronomy and earth and atmospheric sciences. "We found that whether a storm becomes more intense or causes heavy rains could depend on the land conditions - something we'd not considered. Thus far we've looked at these storms based mainly on ocean conditions or upper atmosphere."
Niyogi said tropical storms gain their strength from warm ocean water evaporation.
"The same phenomenon - the evaporation from the ocean that sustains the storms - could be the same phenomenon that sustains that storm over land with moisture in the soil," he said. "The storm will have more moisture and energy available over wet soil than dry."
http://www.eurekalert.org/pub_releases/2009-08/pu-tse082609.php
It goes on to cover using ground moisture in modeling TCs and the expected effect. Wonder how they quantify the "ground" moisture in the Everglades, the Atchafalaya, and the like. (Very little "ground" to be had)
Let me rephrase that... the doomcasters will be out in full force.
Danny will brush the coast and up to NE coast at the most.
you can also see this floater
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It shows the center a little to the west of a new area of convection
Water spout located at Fort Myers Beach around 4:30pm today.
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Thanks for answering. I agree it is very complex, and still somewhat mind boggling if you will. Thanks for the sites too, I will definately read up on it!!
Well if the storm went magically due west, JFV(WeatherStudent)(Drakoen...jk) would be driving the bus.
ignore him
if you say it is going to the sea you are a fishcaster
is you day it is going west you are a westcaster
if you say it could hit someone you are a doomcaster
bahh such an immature thing =\
lol one thing
what storm is named Daniel? xD
its Danny lol
I was not referring to you. Just making a general comment about others that will come on the blog.
I am just a plain ole caster, myself.
75 mph Hurricane at landfall
didn't say it would track due west at any point...just don't see it taking a bill track is all...bill was bigger, badder and bolder than danny...lots of verticle stacking on bill that danny doesn't have
as long as there isn't anything in front of the word caster we are alright xD
I was just making a joke. You are correct about the verticle stacking.
...and our friends on the islands.
UWALKTHEMALL#228 - yikes..good I didn't see that picture before I picked my kid up from the dive boats. I fretted all day till the boat came in. I Trust the Captain and he did a great job... said it was weird weather out there. Storming seems to just sit 20-5 miles off shore. they spearfished just inside the line, keeping a very careful/watchful eye. Kid brought home a FEAST!
we now have half of it here xD
is he related to Kanye West?
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