HURRICANE DANNY FORECAST SYNOPSIS / BRIEF TROPICAL SYNOPSIS…ISSUED AUG. 21, 2015…8:50 P.M. EDT

SEVERE WEATHER THREAT: SLIGHT
TROPICAL STORM FORMATION: DANNY, MEDIUM (40%), MEDIUM (40%), LOW (30%)

ALL forecasts contained on this site,  are based on my analysis and knowledge of various forecast tools, including information contained in NHC products, and are not copies from any other entity.

*NOTE: In the TROPICAL STORM FORMATION line above, probabilities are for during the next 5 day period.  My personal probability will be listed as either NONE, MONITORING or PROBABLE.  This does not necessarily mean something will develop, but that certain forecast conditions are likely to be present, favoring development.  Once NHC products become available, then the appropriate probability and percentage will be used.

Please refer to the link for the Storm Prediction Center in the box at the top of the page, just below the Hurricane Hunter graphics.

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Current Storm Total for 2015:

TOTAL STORMS: 4
HURRICANES: 1
INTENSE HURRICANES: 1
U.S. LANDFALLS: 2

StormW Seasonal Forecast:

TOTAL STORMS:             8
HURRICANES:                   3
INTENSE HURRICANES: 1

Good evening everyone!

There are 3 more areas the NHC is monitoring, and I will mention them briefly at the end of the synopsis, as we have time to deal with them.  The main focus will be Hurricane Danny.

I guess we got a surprise today.  I didn’t doubt Danny would attain hurricane strength, however I really didn’t expect Danny to attain Major Hurricane status.  In fact, I don’t think the NHC did either.  Although, hurricanes this small and tight in structure sometimes have no problem ramping up in less then perfect conditions, especially with the previous OHC map indicating somewhat higher OHC values to his west the other day.

As of the 5: 00 p.m. advisory from the NHC, the following was available on Danny:

5:00 PM AST Fri Aug 21
Location: 14.5°N 49.1°W
Moving: WNW at 10 mph
Min pressure: 974 mb/28.76 in
Max sustained: 115 mph

As of 5:00 p.m., Danny was a CATEGORY 3 Hurricane on the Saffir-Simpson Hurricane Wind Scale.

HURREVAC NHC TRACKING MAP
HURREVAC.DANNY

HURREVAC.DANNY72

Danny continues to move toward the WNW, and I epxect this motion to continue during the next 48 – 72 hours, with a turn a little more westward thereafter.  Currently, Danny is feeling a weakness in the subtropical ridge, located north of the Lesser Antilles.  In fact, in my analysis of satellite loop imagery, various channels, Danny may have a little more of a northerly component.  Based on this, there is a possibility we could see a slight northward shift in model guidance, however based on forecast steering, and the current dynamic guidance, the overall track should pretty much remain close to the same as depicted by the NHC official track, but maybe just slightly more north of the islands.  Based on my analysis, I concur with the NHC track, however I cannot rule out the slight shift north at this time.

00Z DYNAMIC MODEL TRACK GUIDANCE
96L 00Z DYNAMIC GUIDANCE

It is still a little early to produce a very definitive track after the 96-120 hour forecast projections, and future track after this will depend on how much Danny weakens, or even if  remnant remains after interaction with Hispaniola, as Hispaniola is extremely mountainous and has the effect of tearing apart the storms core.  Based on my analysis of the current forecast steering, especially if Danny jogs slightly further north, forecast steering indicates any “remnant” should begin to recurve after is passes Hispaniola.  This would be due to a strong weakness in the subtropical ridge between FL. and the Bahamas.  So, I believe the scenario, based on what I am seeing at the moment, and the trend of the dynamic models forecast from 18Z, any remnant should follow the flow near FL. and the Bahamas.  This COULD allow for the remnant to pass close to the FL. peninsula, before making a fairly abrupt turn to the NE over the Bahamas.  As of the time of analysis, this seems to be the most likely scenario.  IF it misses the weakness, then the second scenario would be it crosses into Cuba, to which I doubt anything would remain thereafter.

Analysis of satellite loop imagery tends to indicate Danny may be already beginning to slowly weaken.  If you notice on the west side, Danny seems “flatter”, as if being pushed to the east.  This is attributed to 2 items…the beginning of increasing SWLY wind shear, and some dry air intrusion on the west side of the storm.  Although not able to bee seen at the moment in RGB imagery, some small outflow boundaries were noted on the west and NW side of the storm, indicating some slight dry air ingestion.  Recent vorticity maps also indicate that Danny has become slightly tilted from SW to NE.  Based on these factors, Danny should begin to weaken later tonight.  The most recent wind shear map indicates SWLY to WLY shear to remain a factor throughout the remainder of the forecast period.

DANNY FLOATER SATELLITE LOOP IMAGERY
avn0-laloDANNY

rgb0-danny

CARIBBEAN WATER VAPOR LOOP
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Even if the remnant of Danny makes it close to FL and the Bahamas, I am not expecting any regeneration due to unfavorable upper level winds remaining in the forecast.

I currently agree with the NHC weakening trend, however I cannot rule out a more moderate weakening if Danny begins to ingest greater amounts of dry air.  In either case, Danny should weaken to Tropical Storm force, prior to passing over the Lesser Antilles.

All interests in the Lesser Antilles should still closely monitor the progress of Danny during the next 72 hours for any significant changes.

NHC 5 DAY GRAPHICAL TROPICAL WEATHER OUTLOOK
two_atl_5d0

Elsewhere, the NHC has designated a MEDIUM (40%) probability of subtropical development for a broad area of low pressure near Bermuda.  Currently, this is still associated with an upper level low, so conditions are just barely marginal for development.  Although upper level winds are forecast to remain less than marginal, slow development may still occur as this system is baroclinic in nature.   Forecast steering indicates this area should move toward the NE, and may approach a few hundred miles within the New England area, before turning more toward the NNE.  I will continue to monitor this area for any significant changes.

EASTERN SATELLITE LOOP
avnEAST-l

A Tropical Wave exiting the African coast is currently disorganized, but is displaying a very pronounced cyclonic circulation.  This area is currently moving toward the west near 25 mph.  Upper level winds are currently favorable over the area, and the current wind shear forecast indicates the current upper level anticyclone to remain over the wave during at least the next 4 days.  Based on this, and a good amount of water vapor surrounding the system, we could see development of this wave over the next 5 days.  However, given the quick forward motion, development would be slow to occur.  I will continue to monitor this wave over the next 96 hours.

EATL SATELLITE IMAGE
avnEATL-l

EATL WATER VAPOR IMAGE
wv-l

RAMSDIS CIRA METEOSAT FLOATER LOOP IMAGERY
tropical_met_4km_visir2_floater

tropical_met_4km_ir4_floater

The NHC has designated LOW probability of  an area within the above mentioned area.  Upon analysis of satellite loop imagery, I believe this feature, and the above wave, may congeal and become one area to monitor.  I will keep tabs on this area for any significant changes.

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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About palmharborforecastcenter

I am a Tropical Forecast meteorologist, providing hurricane forecasts during the Atlantic Hurricane Season. I retired from the U.S. Coast Guard in July of 2001. Meteorology became my passion in high school, and I have continued my educational background in meteorology since 1996, when I undertook the study of Tropical Meteorology. While working toward my degree, I had to unexpectedly withdraw from college due to my oldest sons medical reasons. I do however, meet the educational criteria of the AMS to be recognized as a meteorologist. Studies include, but are not limited to the Navy Aerographers Mate course, Naval METOC meteorology course, Meteorology 2010 Sophomore level course while attending St. Petersburg College, Clearwater, FL., Basic Forecasting course for operational meteorologists from Rapid WX, meteorology institute, a four month meteorological internship, and extensive research on numerous meteorological topics such as the MJO, NAO, satellite imagery interpretation, etc. I have been forecasting Tropical Weather (Tropical Storms and Hurricanes) since 1996, with my main client being three different Coast Guard Commands.
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3 Responses to HURRICANE DANNY FORECAST SYNOPSIS / BRIEF TROPICAL SYNOPSIS…ISSUED AUG. 21, 2015…8:50 P.M. EDT

  1. originallt says:

    Thanks, Storm. –Yeah, Greg, looks like your area is for sure, safe from Danny.

  2. Greg Goodman says:

    Mr storm does it looks like we are safe from danny?

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