TROPICAL WEATHER OUTLOOK FORECAST SYNOPSIS…ISSUED AUG. 13, 2018…7:20 P.M. EDT

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(T. F. “Storm” Walsh III)

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StormW’s 2018 HURRICANE SEASONAL FORECAST

TOTAL STORMS: 12 – 13
HURRICANES: 5 – 6
MAJOR HURRICANES: 2 – 3

2018 CURRENT SEASON TOTALS

TOTAL STORMS: 4
HURRICANES: 2
MAJOR HURRICANES: 0

Greetings everyone!

The NHC still has a LOW (20%) probability that the non tropical low over the far north Atlantic may acquire sub-tropical characteristics during the next 5 days.


The low is currently void of any convection.  It COULD acquire sub-tropical characteristics, as it is supposed to meander near the same location over water temperatures that are warm enough, before moving to the NE and out of the picture.  I’m not too sold on this yet, unless we can see some convection initiate, however the ECMWF and GFS tend to indicate this may develop into a weak system, briefly.  I will monitor this, however it shouldn’t be anything for the U.S. to worry about.

RAMSDIS SATELLITE LOOP (CLICK FOR IMAGE)

Elsewhere, RAMSDIS floater imagery has picked up on a wave in the eastern Atlantic.  A small area of convection is noted, and a weak circulation appears to be present.

RAMSDIS FLOATER IMAGERY LOOP (CLICK IMAGE)

GOES 16 IR LOOP

Based on analysis of forecast wind shear, upper level winds are not forecast to be favorable over the next 5 days, however, upper level winds could relax over the CATL by 8  10 days.  The area to look at is where the blue and white area comes into play between 35 – 55 W and 15N.

GFS WIND SHEAR FORECAST


Neither the ECMWF or the GFS indicate any development of this feature.  I will continue to watch this for any significant changes.

Ok.  I’m going to try and explain what has been happening in the tropics.

Based on some research I have done, I found an explanation from one of my colleagues, Meteorologist Joe Bastardi of Weatherbell.

The setup of the SST anomalies for most of this season, has been warmer in the Pacific, and of course, the colder anomalies in the Atlantic MDR.  This may be a little hard to grasp, but we have a term coined atmospheric memory.  Anomalies are figured through a certain period of climatology.  When anomalies change in certain areas and change in temperature, the atmosphere in a sense “senses” this.  This allows for the various pressure patterns, and how they set up.  In the anomaly map, I have circled the warmer area in black, cooler in red.  What is key here is, it’s not that the SST’s are actually cold in the MDR, or very much warmer north.  It’s not the difference between warm and cold, but HOW MUCH the difference is based on the anomalies.  So, in effect, “Mother Nature” sense the “warmer” anomalies, and pressures “in a sense” become lower in that area, and we get rising air, or lift in the atmosphere.  The “colder” anomalies work the opposite with pressures being sensed as “higher”.  So, this doesn’t actually create high and low pressure systems, it creates higher and lower height anomalies.  This is something similar to what the sea breeze diagram shows.  You’ll note where the warmer temps are, air is rising, and where cooler, air is sinking.

SST ANOMALY CHART

SEA BREEZE GRAPHIC

Since the EPAC was much warmer over the Nino regions, especially 1 & 2, the effect was stronger.  Nino 1 & 2 have cooled, however we still have the anomaly difference regarding the Atlantic.  This is aiding in the sinking air, or what we call subsidence, over the Atlantic, helping to dry the air.  And we have had the added negative of the SAL, due to the stronger subtropical high creating stronger trade winds.

Based on 200 mb vertical velocity potential anomalies, the forecast calls for upward motion by the 15th, however this is forecast to be short lived.  Upward motion is supposed to be favorable for convective development (Blue Contours). However, the ECMWF indicates higher average MSLP anomalies for the next 5 – 10 days Pretty much a wait and see scenario.

200 MB VERTICAL VELOCITY POTENTIAL ANOMALIES FORECAST
ECMWF MSLP ANOMALIES DAY 5 AND 10


I’ll continue to monitor everything, but with my job and all, will only be updating on my time off, unless we have a threatening system.

Have a blessed evening!

T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS
CoCoRAHS OBSERVER

 

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