An active Atlantic hurricane period coming
The remnants of Tropical Depression Five are no longer a threat, done in by high wind shear and close proximity to land. However, an active period for Atlantic hurricanes is likely for the remainder of August, as the global atmosphere undergoes a major change to the circulation pattern that has dominated Northern Hemisphere weather during July and August. A large trough of low pressure is gathering strength over Europe, and is expected to push eastward. By Thursday, this trough should be able to push away the blocking ridge of high pressure that has given Russia its worst heat wave in history. The shift in circulation has already weakened the large region of sinking air that has brought dry, stable conditions to the tropical Atlantic over the past month. Vertical instability, which was unusually low since late July, has now returned to near normal levels over the tropical Atlantic (Figure 1), though it remains quite low over the rest of the North Atlantic. Instability is measured as the difference in temperature between the surface and the top of the troposphere (the highest altitude that thunderstorm tops can penetrate to.) If the surface is very warm and the top of the troposphere is cold, an unstable atmosphere results, which helps to enhance thunderstorm updrafts and promotes hurricane development. Since SSTs in the Atlantic were at record highs and upper tropospheric temperatures were several degrees cooler than average in July, enhancing instability, something else must have been going on to reduce instability. Dry air can act to reduce instability, and it appears that an unusually dry atmosphere, due to large-scale sinking over the Atlantic, was responsible for the lack of instability. Now that vertical instability has returned to near normal levels, Atlantic hurricane activity should increase to at least average levels over the next two weeks. This is particularly true since SSTs are at record highs and vertical wind shear is at average to below average levels over the tropical Atlantic.
Figure 1. Vertical instability (in °C) over the Caribbean (left) and tropical Atlantic between the Lesser Antilles Islands and coast of Africa (right) in 2010. Normal instability is the black line, and this year's instability levels are in blue. The atmosphere became much more stable than normal in both regions at the end of July. This lack of instability also extended to the Gulf of Mexico and North Atlantic Ocean between Europe and North America. However, in the past few days, vertical instability has returned to normal, thanks to a major pattern shift in the global atmosphere. Image credit: NOAA/CIRA.
Figure 2. The climatology of Atlantic hurricane activity shows a sharp rise in activity around August 18.
Analysis
August 18 historically marks the point where Atlantic hurricane activity makes a major spike upwards (Figure 2.) On average, we can expect to see two named storms and one hurricane during the last half of August. The last half of August usually sees a moistening of the atmosphere off the coast of Africa, as the the African monsoon kicks into high gear. This year is no exception (Figure 3.) The dry Saharan Air Layer (SAL) has retreated to the north, leaving a moist atmosphere conducive for tropical cyclone development off the coast of Africa.
It would not be a surprise to see atmospheric instability increase to above-average levels by early next week as the major atmospheric pattern shift progresses. Will this usher in a hyperactive period of Atlantic hurricane activity next week, with a parade of three or four simultaneous storms strung out across the Atlantic? Probably not, since the Madden-Julian Oscillation (MJO) only marginally favors upward motion over the tropical Atlantic, and is not forecast to change much over the next ten days. The Madden-Julian oscillation is a pattern of enhanced rainfall that travels along the Equator from west to east. The pattern has a wet phase with large-scale rising air and enhanced thunderstorm activity, followed by a dry phase with large-scale sinking air and suppressed thunderstorm activity. Each cycle lasts approximately 30 - 60 days. When the Madden-Julian oscillation is in its wet phase over a hurricane-prone region, the chances for tropical storm activity are greatly increased. The bottom line: I expect we will see 2 - 3 named storms in the Atlantic by the end of August, including one hurricane. Where these storms might develop and move is difficult to say. It currently appears that the global shift in circulation will bring near-average steering currents to the Atlantic over the next ten days, with a series of troughs of low pressure capable of recurving hurricanes, moving across the Atlantic. The GFS model is indicating, though, that during the few days of August, these troughs may weaken, making recurvature of hurricanes less likely, and increasing the probability of landfalling storms.
The GFS, NOGAPS, and ECMWF currently predict that one or two tropical storms will form between Africa and the Lesser Antilles Islands during the period 4 - 10 days from now. The NOGAPS model is predicting the development of a strong tropical disturbance near the coast of Honduras late this week.
Figure 3. Saharan Air Layer (SAL) analysis shows that the dry air and dust of the SAL (orange colors) lies well to the north of the hurricane breeding grounds off the coast of Africa, near the Cape Verdes Islands. Image credit: University of Wisconsin/NOAA Hurricane Research Division.
Smoke bedeviling Moscow again
Light easterly winds over the past few hours have brought smoke from wildfires back into Moscow today. Temperatures at Moscow's Domodedovo airport hit 29°C (84°F) today, which is 11°C (20°F) above average. The latest forecast for Moscow predicts that just one more day remains for Russia's greatest heat wave in recorded history. On Thursday, a strong trough of low pressure will move through European Russia, finally bringing below average temperatures.
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 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 — Blog Index
It is *possible*, but the determined troll can spoof his IP address without a great deal of effort, so it is only of marginal use.
Read the Rules of the Road and you'll see why that is impractical.
nope you cant ban just one IP address it is a DNS issue
Pouch synopsis indicated that there might be a Fujiwhara affect between PGI30L and PGI31L, with PGI31L becoming dominate.
I think I'm sorry for asking! But this may be part of why the season has started off with so many TUTT's, dry air and shear?
Most home networks are working on DHCP (Dynamically assigned IP address)....so it is possible, but unlikely that you could narrow it to a single IP address!
WunderBlogAdmin
WunderBlogAdmin is a generic handle used by our employees to interact with bloggers. This gives a single point of contact for our members to report issues and dispute bans. As noted in our terms of service, Weather Underground does not maintain 24/7 watch over the blogs and administration is not real time. Administrators will deal with problems and answer notes when they can, so please be patient.
For questions about these rules please contact WunderBlogAdmin.
The only storm I remember from 1979 was Frederik........and I hope to never see another one take that track as long as I live in Mobile.
made landfall but barely
David made landfall near West Palm Beach, then moved due north 30-50 miles offshore the Florida East Coast before making a second landfall in Savannah. I remember David very well as it happened on Labor Day weekend that year. Here in Jax, we stayed on the weaker side of David, but still got tropical storm force winds of 50-60 mph and heavy squalls as he passed just east of Jax.
Another important point...
Here are the forecast error trends:
We're talking about a 300 mile error - on either side of a forecast point - at 120 hours.
We're talking about much more than that now.
And, that's with an established COC... not a bunch of clouds like now...
Still plenty of time...
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT TUE AUG 17 2010
FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...
SHOWERS AND THUNDERSTORMS HAVE INCREASED IN ASSOCIATION WITH A
TROPICAL WAVE LOCATED OVER THE CENTRAL CARIBBEAN SEA. SURFACE
PRESSURES ARE NOT FALLING SIGNIFICANTLY...AND ANY DEVELOPMENT OF
THIS SYSTEM IS EXPECTED TO BE SLOW TO OCCUR OVER THE NEXT COUPLE OF
DAYS. THERE IS A LOW CHANCE...10 PERCENT...OF THIS SYSTEM BECOMING
A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES GENERALLY
WESTWARD AT 10 TO 15 MPH.
ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
$$
FORECASTER KIMBERLAIN/PASCH
UTC EST EDT
0000z 7:00 pm 8:00 pm
0300z 10:00 pm 11:00 pm
0600z 1:00 am 2:00 am
0900z 4:00 am 5:00 am
1200z 7:00 am 8:00 am
1500z 10:00 am 11:00 am
1800z 1:00 pm 2:00 pm
2100z 4:00 pm 5:00 pm
Huh? I ban 1 IP all the time in phpbb. (or a range of addresses).
Link
This comment has been removed for violating the Community Standards.
Pat - how do these messages come up if no one's watching? Just asking...Thanks. Mel
ABNT20 KNHC 171732
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT TUE AUG 17 2010
FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...
SHOWERS AND THUNDERSTORMS HAVE INCREASED IN ASSOCIATION WITH A
TROPICAL WAVE LOCATED OVER THE CENTRAL CARIBBEAN SEA. SURFACE
PRESSURES ARE NOT FALLING SIGNIFICANTLY...AND ANY DEVELOPMENT OF
THIS SYSTEM IS EXPECTED TO BE SLOW TO OCCUR OVER THE NEXT COUPLE OF
DAYS. THERE IS A LOW CHANCE...10 PERCENT...OF THIS SYSTEM BECOMING
A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES GENERALLY
WESTWARD AT 10 TO 15 MPH.
ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
$$
FORECASTER KIMBERLAIN/PASCH
Looks like someone watched "Knowing" last night. :)
is it possible the CMC is not showing a trough split with that system in the Gulf but instead it is this system in the Caribbean?
remember as crazy wacked out as the CMC has been, it was the only model to get Bonnie right, so it can show some flashes or brilliance
Thank you Storm! So, another quick question: the model runs...do they start running at 0Z (for example) or I can get the completed run at 0Z. How does it work?
I am constantly refreshing the models page and it would be easier to know at what time approximately I should check on them. Thanks again!
Try going back a page in the discussion and resetting, then come back to the current page - I have that same issue once in a while.
Thanks for the graph Tampa, it just further supports my contention that beyond 72 hours, models become very unreliable.
Thanks!
Viewing: 451 - 501
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 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 — Blog Index