Issac Intensifying tonite- Eye appears to be forming

Tonite, things seems be going from bad to worse for Haiti.  Over the last 5 hours Issac has been going through intensification and slowing down as it approaches Haiti.  The Hurricane Center will report the latest finding in 10-15 minutes.  The pressure has been falling all evening and to the east in the Dominican Republic, Barahona reported 50 MPH gust but they have not reported in nearly 3 hours.  There have been no hourly observations from Port Au Prince for about the last 4-5 hours.  As long as Issac remains off shore, it will likely intensify before going onto land. 

My reading based on Reports from CNN is that people are still in the tent cities.  I do not think that they will be able to stand up to strong tropical storm force wind for very long.  The heavy rain is also on the way.  Clearly not the best scenario developing tonight for Haiti.  The shortwave IR and now IR images show that a small eye seems to be developing.  Should be confirmed by aircraft over the next few hours.

Issac Organizes itself -- Haiti -- prepare for impact

Friday 8/24 11:45 Visible Image of Issac

Well, it looks like Issac after being disorganized with multiple centers and having a track that was south of the the Greater Antilles is making its move north.  It is organizing around a central center which was not obvious in the last 3-4 days.  Issac has increased from 45 MPH to 60 MPH since 5 AM this morning and appears to be strengthening while moving NW taking it on a track to intersect Haiti.  Based on its current motions, the weather should being to worsen in the next few of hours in Haiti.  Depending on the exact track, the Issac may not weaken much as it will may not interact with the mountains.   Residents should expect winds of 30-60 MPH with higher gust, but the rain will be extremely heavy with life-threatening flash floods in Port au Prince and northward to Gonaives.    The next 24 hours will be difficult.

There is still uncertainty on where this storm is going after it impacts Haiti and Cuba.  But no one should be at ease because Issac may be stronger and more organized than initially anticipated.  The cone of uncertainty is very large with land-fall anywhere from Florida to Louisiana by Wednesday.  There is even more uncertainty on how strong it will be at that point.   Now we must hope and pray for the people of Haiti to remain strong and for the impacts to be minimal.   But the time of trial is upon them.

What's going on? Issac?

This morning, there is a much confusion about Issac as there is about the economy.  Where is the center of this storm?  This reminds me of Tomas in 2011 when it was unclear how the storm would evolve once it reached the Caribbean sea.  Issac has all of the good environmental conditions that should make it intensify and yet there has been no action -- nothing to write home about.  Over night the center of the storm seems to have moved south and the hurricane hunters are finding multiple centers of rotating air.  Well maybe there is still a lot to learn about hurricane intensity. 

There is still the feeling that the storm will impact Haiti sometime tomorrow and then move towards the northwest.  However the confidence in the track and intensity are not so high in my opinion. 

The other issue:  Focus.  There is more stories on how the republican convention might be disrupted by Issac than about how the population of Haiti will be disrupted.  There are hundreds of thousands of people in Haiti living in camps. CNN says 421,000 people.   The convention will be moved somewhere else and the loss of life will be minimal.  But for the people of Haiti, it is not possible to move anywhere except away from local dangers such as rivers that will overflow.  They cannot run from the wind or rain if Issac were to make landfall.  Even with the new houses that have been built by the government it is not enough to cover all of the people as it will take more time to provide shelter for many of those who survived the Earthquake.

In a strange way, the longer it takes for Issac to develop, the more dry air that is available and the longer it takes for the center to come together, the better for the people of Haiti.  They need more time to protect the vulnerable and rebuild houses and neighborhoods.  But this must happen quickly, because eventually a hurricane will strike Port Au Prince.

Haitan Camp in Port Au Prince (Washington Post)

I think that the ECMWF forecast has the right trend and that there may be a more westerly track to this storm.  Even that is uncertain, but everyone from Haiti, Cuba, Florida and the Gulf States need to be ready.  It is still too early in the hurricane season and pattern of high pressure over the Eastern and Central Atlantic has been pretty persistent over the last few months.  Later in September, the evolving El Nino should bring more shear and the frequency of troughs should help to steer some of these storms out to sea.  But uncertainty is in the air, we just have to live with it and stay vigilant.   No of us are in the clear -- even in Washington DC. 

TC Issac Reload

Tonight Tropical Storm Issac makes it way westward into the Caribbean.  Tomorrow it will begin impacting the islands.  This has been a very strange hurricane season.  We have named storms very early on (May and June).  We have had two hurricanes (Ernesto and Gordon).   Issac is a tropical storm and forecast to become a hurricane.  The storm track has been favoring the Caribbean sea, but there has also been so much dry air coming across the Atlantic from the Sahara and the storms have been moving fairly fast over the last couple of weeks.  Hence, thus far the storms have been nothing to write home about. 

This Issac reminds me of a time 6 years ago when its predecessor (Issac) was taking shape off the Guinea coast on about the 19th of September 2006.  The French Falcon aircraft was stationed in Dakar Senegal in the third phase of the Special Operations Period (SOP-3) of AMMA.  All of the forecast were suggesting development of a storm off the coast and I felt confident about it also.  The aircraft team went our suggestions and when they arrived there some 2 hours later -- nothing....  The disturbance was there in the wind field but not clouds, no developing cyclone... a waste of fuel.  Yeah I felt bad about it but it turns out that the disturbance did form much later over the Central Atlantic.  It evolved into a minimal hurricane over the Atlantic that posed a threat to no one.

But can we say the same for Issac that is about to enter the Caribbean Sea?  I don't think so.  It has been organizing itself slowly even with dry air to the north that has inhibited the storm from developing.  There is low shear over the Caribbean sea and the ocean temperatures are warm.  The track of the storm is carrying it toward Haiti.

However, there has not been lots of consensus on where this storm is going or its intensity.  In the short term they all seem to take it into near Haiti, but after the ECMWF model carries it towards western Cuba while some of the others carry it towards Florida.  The strength of the storm is also unclear, because if it does interact with Haiti (which I hope that it does not), the mountains will disrupt the circulation and weaken the storm.  It seems that the storms this year have been difficult to forecast at least in the early stages so we will stay tuned.    But in the meantime, we are ramping up into the heart of the hurricane season.  It is not a bad idea to check and make sure that you have your emergency kit and know where all of your important documents are located. 

You never know.....

Maybe Issac 2012 will outshine its 2006 predecessor

Dry air Impacts on Senegal Rain

So the question that we struggle with is how did this situation come about??  It is a bit technical, but anytime you have a factor that last more than a few weeks, there is a large scale pattern that is at work.  Below I have a few examples of satellite based rainfall movies of how the dry air near the coast is disrupting precipitating system.

Case 1 July 23-24

This is a line of convection that formed during the evening and moved towards the coastline.  Under normal conditions, this type of storm would definitely reach Dakar with heavy rain.  The opposite happens in this case where the observations show that dry air is locked in 200 meter.


Case 2 (Squall line from Mali
July 31 - August 1

In the second case, a relatively strong squall line came across Mali and entered eastern Senegal during the early morning hours.  At 0600 UTC (2 AM US east coast)  the picture show rain rates and the squall line entering eastern Senegal.  But the dry air is still locked in Senegal.  Here is the movie of the line today.

The good news is that even Dakar, did receive some rain this afternoon. But the situation
needs to be watched.

Senegal Dust, Dry Air the possible collapse of the rainy season

During the month of June when I and several students were in Senegal to install new equipment and to examine new data from a ceilometer that was put in last year, we noticed that Saharan dust was being observed in the lowest 500 meters (0-1500 feet).  This was a strange thing given that dust is often found between 1000-3000 meters or some 3000-10000 feet above the ground.  So as the picture for June shows above green represents dust aerosols and the are trapped below what is called the marine boundary layer.   Unfortunately this means that the dust cannot be dispersed but has remained in place.  But since we had never seen this before for Senegal we were skeptical.

There were days that the dust was apparent such as June 18 and 19th when there large amounts of dust flowing over Senegal.  However, this dust was above the layer that we continued to see day after day.  On these days we could see how the Sun was obscured by all of the dust in the air.

 

However, in the layer with the dust, we also noticed that the relative humidity was something line 1% between 600-1200 feet above the ground.  Initially we figured that there was something wrong with the instruments for measuring relative humidity (radiosondes).  However after looking at this situation more closely we now know that it is not an instrument problem.  As an example here is the relative humidity from the week of July 17 and it is very clear that there is a layer of very dry air over Dakar every day during this week. 


So you say so what to all of this???  Is it really that serious.  The answer is Yes.  Why?

1.)  The dust is unhealthy to breath in.  The particles are so small that they get trapped in your lungs.  Hence you feel really sick.  If you have asthma -- you have real problems breathing and given the state of the health care system in Senegal and the access to resources many people will get sick.  The dust most likely carries Mengintis which can lead to death if not treated.   Early indications are that Meningtis rates have increased across the entire country. 

2.)  The very dry layer with the dust creates a very stable layer which tends to disrupt rainfall.   Thunderstorms and other forms of organized rain prefers the opposite situation, with unstable air not no dry air.  There have been two heavy rain events thus far but most of the organized systems have fallen apart as it travels across Senegal.  Tomorrow begins the month of August with the highest rain amounts normally.  However, I believe that below normal rainfall is a strong possibility unless this pattern stops. 

Both reasons put millions of people in and around Dakar along with the other coastal cities at risk.  The early analysis suggest that the dusty air is coming from Western Sahara.  The dry air is probably coming from two sources: the Subtropical Atlantic and sinking over Dakar and from the Western Sahara.  

So how long has this been going on?  Since May..  For nearly 3 months.  When will it end??? No one knows.

Even thought a tropical storm is possible in the next day impacting the Caribbean, this pattern is not conductive to tropical storms forming over the Eastern Tropical Atlantic.  They will have to wait until they are away from the dry dusty air. 

I will continue to update.   As of now, there has been no change in status.  The dust and dry air remains in place this week.

Wild Swings in the Climate during 2012

I have been planning to post about the observed weather and climate for many months now.  Just too many things happening with life, teaching, research and students.  But here is a review of some of the key items:

1.)  A warm dry winter across much of the US.  For example Washington DC (National airport) observed :
-- December - Trace of Snow, Temperatures 5.3 degrees above normal
--January - 1.7 Inches, temperatures 4.7 degrees above normal, temperatures of 60 degrees or higher occurred 6  times.
- February - 0.3 inches of snow, temperatures 5.4 degrees above normal.  A maximum temperature of 72 degrees on February 1st.

The warmth continued to March with temperatures being 80 degrees or higher on 4 days during the month of March. 


2.)  Dry conditions then followed with a deficit of rain during March (-2.46 inches), April (-1.14 inches), May (-0.71 inches) and June (-1.4 inches of rain). 

3.)  Because much of the US had little snow and hence dry going into the spring, wildfires broke out
in the Western US. 

4.)  In Washington DC, the heat in June/July has been unbearable.  There were 11 days in June with temperatures 90 or above and 7 that were 95 or above.  The hottest day was June 29th with a temperature of 104 was recorded and later that evening the Derecho event came plowing through DC
causing massive blackouts and damage.  Winds were clock at 70 MPH at national airport with higher gust being reported.

July has outpaced  June with 15 days thus far being above 90 degrees at National Airport.  Twelve of the 15 days have been hotter than 95 degrees and six days have been 100 degrees or hotter.

Maybe all of this is all coincidence but looks like climate projections from the models. Regardless of what the models project, dealing with temperatures that are above normal are problematic for even the best of us.  The impacts such as wildfires because of reduced snow often manifest themselves later.  The additional power for cooling our homes and driving in traffic just add greenhouse gases to the atmosphere -which should ultimately lead to more warming.   The additional power puts lots of strain on the electric grid.  I wonder how we get out of this????  By the way, its not over yet.  August it typically your warmest month.

In the next blog, will focus on the changes in the atmospheric conditions in Senegal that are causing serious problems and the impacts on the upcoming hurricane season.