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posted on 28 September 2017

Farewell Maria, Finally - 28Sep2017

Written by Sig Silber

12:50 PM EDT Sept 28, 2017: LATEST FROM NHC: "...MARIA BEGINNING TO ACCELERATE AWAY FROM THE UNITED STATES..." "The cyclone is expected to move in a general easterly direction for the next 12-24 h...Afterwards, Maria is accelerate toward the east-northeast at forward speeds in excess of 30 kt by 36 h."

Special Landing Graphic - Farewell Maria

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In this Article we are gong to focus mainly on the Atlantic. Notice there are two storms there: Maria and Lee. More on that later.

Eastern Tropical Pacific 

Note possible new storm to worry about. It does not appear to be more than a rainmaker but we will keep an eye on it.

Tropical Weather Outlook NWS National Hurricane Center Miami FL 800 AM EDT Thu Sep 28 2017

A large area of cloudiness and showers extending from the northwestern Caribbean Sea across Cuba to the Bahamas is associated with a broad surface trough interacting with an upper-level low. A weak area of low pressure is likely to form from this weather system while it moves northward across Cuba and near the east coast of the Florida peninsula during the next few days, and environmental conditions appear conducive for development before upper-level winds become less favorable early next week.  Regardless of development,  this system is likely to produce locally heavy rainfall over portions of Cuba, southern Florida, the Florida Keys, and the Bahamas during the next several days.

* Formation chance through 48 hours...low...20 percent.

* Formation chance through 5 days...medium...40 percent.

This graphic looks out a bit further into the future. It is an analysis of projected tropical hazards and benefits over an approximately two-week period.

Tropical Hazards

Notice in the forecast for September 27 through October 3 the area west of Central America has the potential for cyclone development and the following week the forecast is that both the Caribbean and Pacific side have the potential for cyclone development. 

We start our Report with Hurricane Maria. The"M" Designation means a very powerful storm: Category 3 or higher.  Notice that Maria no longer categorized as "M".  In fact it had been downgraded to Tropical Storm Designation but has just now been upgraded to a Cat 1 Hurricane.

Tropical Depression 15

Experimental Wind Arrival Analysis

And the Discussion for Maria which was upgraded on Wednesday to Hurricane Status and downgraded overnight back to Tropical Storm Status.

Tropical Storm Maria Discussion Number 50 NWS National Hurricane Center Miami FL  1100 AM AST Thu Sep 28 2017

A burst of strong convection containing cloud top temperatures colder than -70C has developed just east of the center since the previous advisory. Based on the recent inner-core convective development and a Dvorak current intensity estimate of 3.5/55 kt, the initial intensity estimate is being maintained at 60 kt for this advisory. Also, the last AMSU overpass around 0200 UTC indicated that Maria has retained tropical characteristics based on a deep warm core that extends from near the surface to above the 200 mb  level, accompanied by a warm anomaly of more than 2.5 deg C, present in the upper-levels of the cyclone.

Maria is now situated on the north side of a strong deep-layer ridge, and the initial motion estimate is now toward the east or 085/11 kt. The cyclone is expected to move in a general easterly direction for the next 12-24 h along the northern edge of the aforementioned ridge. Afterwards, Maria is forecast to get caught up in west-southwesterly flow ahead of an approaching deep-layer trough that is currently located over the Great Lakes region, causing the cyclone to accelerate toward the east-northeast at forward speeds in excess of 30 kt by 36 h. The new track guidance remains in excellent agreement with cross-track differences of only about 60 nmi and speed differences of just a couple of knots. As a result, little change was made to the previous advisory track, and the new NHC forecast lies down the middle of the guidance envelope, close to the various consensus models.

Little change in intensity is forecast during the next 36 h or so while Maria remains over SSTs of 26C-27C and the vertical shear is less than 10 kt. By 36 h and beyond, Maria will be moving over sub-25C SSTs, reaching 21 deg C water by 48 h. The colder water, along with increasing wind shear and dry mid-level humidity values of less than 40 percent, should induce some weakening. Maria is expected to become extratropical by 72 h due to these unfavorable  dynamic and thermodynamic conditions. However, given the very cold water that will exist beneath the cyclone, it is possible that Maria could become extratropical as early as 48 h. The extratropical low is expected to be absorbed by a larger low or frontal system over the northeastern Atlantic by 96 h, before the low moves across Ireland. The intensity forecast remains in agreement with guidance provided by the NOAA Ocean Prediction Center.


INIT  28/1500Z 36.8N  69.3W   60 KT  70 MPH

29/0000Z 36.9N  66.7W   55 KT  65 MPH

24H  29/1200Z 37.4N  62.1W   55 KT  65 MPH

36H  30/0000Z 38.8N  56.1W   55 KT  65 MPH

48H  30/1200Z 41.3N  48.8W   55 KT  65 MPH

72H  01/1200Z 47.9N  31.2W   45 KT  50 MPH...POST-TROP/EXTRATROP

96H  02/1200Z...DISSIPATED




Here is the track of Hurricane Lee

Hurricane Lee Track

More of an oddity than a major threat to any populated but this Hurricane which had just been drifting around looks to merge with Maria fairly soon.It is pretty interesting how that works

 Maria Wind Speed Probabilities

 Hurricane Lee is shown off to the right! Is that the Fujiwhara Effect? Are they trying to merge? It looks like that. Click here for an interesting animation of how this might play out.

Fujiwhara Effect


General Weather Situation

We believe that it is easier to understand what is going on with individual storms if they are put into the context of the overall weather situation.

Three day

The graphic above is particularly useful as it shows the forecasted conditions that might determine the future of a storm beyond the predictions of where the storm might be on Day 3. This graphic is updated frequently. By Day 3 Maria is off Newfoundland with Lee and not getting a lot of attention. You can see the Tropical Wave over Florida.

Additional Graphics

Day 1 Forecast Map

This is the Day 1 Forecast. You can see now Tropical Storm Maria way off shore

Day 2 Forecast

This is a Day 2 Forecast.  Tropical Storm Maria is no longer on this map.

This is a national animation of weather fronts and precipitation forecasts with four 6-hour projections of the conditions that will apply covering the next 24 hours and a second day of two 12-hour projections the second of which is the forecast for 48 hours out and to the extent it applies for 12 hours, this animation is intended to provide coverage out to 60 hours. This graphic is very relevant as one can see both storms of most interest in this graphic. .

current highs and lows

The explanation for the coding used in these maps, i.e. the full legend, can be found here although it includes some symbols that are no longer shown in the graphic because they are implemented by color coding.

Precipitation Forecast

You can see the forecast for seven days of cumulative precipitation. It is important to keep in mind that these are forecasts going forward. Precipitation that has already occurred does not show up in these forecasts but will show up in the 30 day maps we show in our weekly Weather and Climate Report. Some of these impacts show up in the September 25 Report that was published Monday evening click here to read. Florida is now on the radar also and in a big way..

 Water Vapor Imagery

The water vapor imagery is a good guide to where precipitation is occurring. One sees Hurricane Maria substantially off shore. New tropical disturbance south of Florida (right now it is still south of Cuba).


Click here for a list of Sig Silber's Weather Posts

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