HURRICANE WORKS/TROPICAL WEATHER WATCHERS UPDATED DISCUSSION
Supercane and I have been continuing to do research on the subject and we have decided to post another discussion....
Before I begin, I will post the previous two timing of hurricane season posts. That way, you can compare our orginal forecasts to what has occured so far this season. The updated discussion will be available under the first two discussions.
MJO Discussion #1
TropicalWxWatcher, I, and a few others have been doing some research on how the MJO will come
into play this hurricane season. In this topic, I will discuss the current status of the MJO,
then the prediction of it throughout the season and how it will affect the number of tropical
cyclones all year (in the Atlantic basin).
Since June 15, we have been in a dry MJO phase. This MJO is moving rather fast, and its center is
already in the eastern Caribbean Sea. If time is right, this dry MJO should exit the Atlantic
basin during the first 10 days of July. From now to early July, we should see no tropical cyclone
formation occur, except for maybe 1 TS.
After that, a wet phase MJO should come into the Atlantic, around mid July. This wet MJO should
last until mid August. During this time, we should see several named storms, but not much in the way of hurricane decelopment. In other words, we should see a nice outbreak of tropical
cyclone activity during this time (mid July to mid August).
Then, another dry MJO should come into play. This dry MJO will probably last from mid August to
early September. During this time, we will probably see a lull in tropical cyclone activity. If
the timing of the MJO is right, we should see a few named storms, maybe a hurricane, but no major
hurricanes (mid August to early September).
After this dry MJO exits, a wet phase MJO will again enter the Atlantic basin around mid
September. This MJO will probably last from mid September to mid October. During this time, we
should see a large outbreak. Assuming there is a wet phase MJO during this time, I except we'll
see numerous named storms, several hurricanes, and around two major hurricanes (mid September to
mid October).
Afterwards, another dry MJO will come into the Atlantic. This will probably last from mid October
to November. During this point we should see almost no tropical cyclone activity, except maybe a
named storm or two. By the time this MJO exits, the hurricane season will be almost over, and a
weak El Nino may be forming.
SUMMARY/CONCLUSION: [/I]
Jun 01 -- Jul 05: Significantly CALM
Jul 10 -- Aug 10: Moderately ACTIVE
Aug 15 -- Sep 15: Moderately CALM
Sep 20 -- Oct 20: Significantly ACTIVE
Oct 25 -- Nov 30: Significantly CALM
If the MJO assumption is right, expect most of this years activity to occur in late September with a moderate burst of moderate activity in late July. But this could be very far off, since the timing of the MJO varies.
[B]MJO Discussion #2
This is an update on the Madden Julian Oscillation and a comparison to the active 1995 hurricane season. The original forecast was first posted a week ago. Supercane also took part in the forecast.
Before I begin, just take a look at some data containing information about the 1995 Atlantic hurricane season...
# Name Dates
Hurricane ALLISON 03-06 JUN
Tropical Storm BARRY 06-09 JUL
Tropical Storm CHANTAL 13-20 JUL
Tropical Storm DEAN 28-31 JUL
Hurricane ERIN 31 JUL-03 AUG
Tropical Depression #6 05-07 AUG
Hurricane FELIX 08-17 AUG
Tropical Storm GABRIELLE 09-12 AUG
Hurricane HUMBERTO 22 AUG-01 SEP
Hurricane IRIS 22 AUG-04 SEP
Tropical Storm JERRY 22-25 AUG
Tropical Storm KAREN 26 AUG-03 SEP
Hurricane LUIS 28 AUG-11 SEP
Tropical Depression #14 11-13 SEP
Hurricane MARILYN 12-22 SEP
Hurricane NOEL 27 SEP-07 OCT
Hurricane OPAL 27 SEP-05 OCT
Tropical Storm PABLO 05-07 OCT
Hurricane ROXANNE 07-20 OCT
Tropical Storm SEBASTIEN 20-24 OCT
Hurricane TANYA 27 OCT-02 NOV
http://www.aoml.noaa.gov/hrd/Landsea/95Season/fig13.gif
These storms tended to cluster during two active periods (30 July-29 August, and 27 September-27 October). Note the relatively inactive period 30 August and 26 September, that coincided with the normal climatological peak in activity.
We aren't predicting a season as active as 1995. However, we will likely see a very active season compared to the long term average. If you could lower the frequency of tropical storms during the 1995 season, the season would look almost identical to our latest MJO and tc activty forecast. We are forecasting two active periods of activity. If our forecast verifies, the TIMING of the season would be extremely similar to 1995, but not as active as 1995. During the 1995 season the month of September experienced slightly BELOW average activity. We do expect a few storms to develop during the month of September. However, the peak of activity shouldn't occur until late September instead of early to mid September. Why? Well you guessed it, the MJO.
Experts don't believe that the Madden Julian Oscillation was the cause for the below average amount of activity in September of 1995. They believe the lull was in response to geopotential height anomolies over North America and cooler ssts which moderated due to the storms that developed in the month of August. However, we believe that the Madden Julian Oscillation at least had some influence. Researchers didn't know as much as they do now about the MJO.
The "wet" phase of the Madden Julian oscillation has now made its way into the Gulf of Mexico. As a result, we see a burst of convection in the western GOMEX. Its amazing how this oscillation works while moving across the globe. The MJO won't move into the central Atlantic Ocean until sometime around July 5th. This is when we begin to look for signs of an increase in overall activity. This was also stated in our orginal forecast... Jul 10 -- Aug 10: Moderately ACTIVE
So far, our forecast has verified well. We forecasted conditions to become slightly more favorable by the 10th of July. The wet phase of the MJO should be over the central Atlantic roughly sometime near the 10th, resulting in slightly more favorable conditions. Now you won't see a dramatic change. Afterall, we are still talking early to mid July. But there should be some slight improvement overall.
UPDATED DISCUSSION (AUGUST 17, 2002)
Our Madden Julian Oscillation and its influence on the 2002 Atlantic hurricane season forecast is continuing to verify. In our first discussion, we forecasted an inactive period between June 1st and July 5th. This section of the forecast easily verified as we had no tropical development during this period. Between July 5-10 we forecasted a transitioning period across the Atlantic from a dry MJO phase to a wet MJO phase. Obviously, we were correct. The negative "wet" MJO phase moved into the Atlantic by the 10th of July. Since we forecasted the negative MJO to move into the basin by July 10th, we forecasted an increase of activity between July 15th and August 15th. The forecast of moderate activity during this period also verified...
# Storm Name Dates Pres
1 Tropical Storm ARTHUR 14-16 JUL 997
2 Tropical Storm BERTHA 04-09 AUG 1008
3 Tropical Storm CRISTOBAL 05-08 AUG 999
All of our named storms so far this season developed in this period with the exception of Arthur, which developed one day too early. So I would say that our forecast has verified nicely. Will our forecast continue to verifiy through the season? Here is an update on our thoughts for the remainder of the 2002 season...
For the August 15 through September 15th period , we forecasted moderately calm activity, opposed to the significantly calm forecast between June 1 and the 15th of July. While we do believe that we will see tropical development during this period, it won't be as active as what it could be. Why? Well, the positive "dry" phase of the Madden Julian Oscillation is still present over the Atlantic basin and it will take 2-3 weeks before the Atlantic finishes going through another transitioning period. Since mid July, the negative "wet" phase of the Madden Julian Oscillation has been building over the Pacific Ocean. Currently, the wet phase extends from eastern Asia, all the way to the west coast of the United States. The negative phase of the MJO should continue to slowly propagate eastward. Now unless we begin to see another shift in the global pattern, the negative phase should begin to have an influence on tropical activity by September 20th. In June, we forecasted significant activity between September 20 through mid October. We could see a significant increase in activity a week sooner since the MJO is moving a bit faster than we expected.
Now late October and November is a little tricky. A few months ago, Supercane and I forecasted significiantly calm activity during this period. This was due to the forecast of a moderate El Nino beginning to set in by then. Now our forecast hasn't changed due to any changes on the ENSO forecast. By November, 99% of the tropical activity should be over with. So El Nino still isn't expectred to supress activity. However, during El Nino seasons, we typically see an increase in SUBTROPICAL activity. So with El Nino continuing to develop, we could see more subtropical activity during late October and November then previously forecasted. Now this would only be moderate activity but it would still increase our number of storms this season.
Other factors...
Now we all know that the Madden Julian Oscillation is certianly not the only factor. The North Atlantic Oscillation is another factor that you don't hear a whole lot about. Basically, a negative North Atlantic Oscillation (NAO) means warmer than average sea surface temperatures across the Atlantic basin, with slightly more favorable conditions in the western Atlantic and the Gulf of Mexico. Currently, we are in a negative NAO phase. This is why the ssts off New England are so warm. The negative NAO also caused conditions in the west Atlantic to become more favorable, which allowed our three tropical systems to develop. Long range CPC models continue to show the NAO going into the tank. IF the NAO stays negative long enough, we could see ssts off the coast of Africa warm. Now the sstas have already moderated a bit over the past month or so. We will just have to see if the warming trend (its a very slow trend btw) continues.
The factor catching the most attention lately, has been the strong Azores high. The Azores high is extremely WEAK. The highest pressure associated with the high is 1022MB! That is BELOW the average. The high will NOT strengthen over the next few days. In addition, the strong upper low over the central Atlantic could limit the amount of subsidence over the central Atlantic in a few days. This COULD open the door for possible development in this area. I will try to get to that in my daily discussion (Hopefully I will be able to update it later today.
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