TROPICAL STORM DANNY FORECAST SYNOPSIS…ISSUED AUG. 18, 2015…9:25 P.M. EDT

SEVERE WEATHER THREAT: SLIGHT
TROPICAL STORM FORMATION: DANNY

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: 0
INTENSE HURRICANES: 0
U.S. LANDFALLS: 2

StormW Seasonal Forecast:

TOTAL STORMS:             8
HURRICANES:                   3
INTENSE HURRICANES: 1

Good evening everyone!

All I can say is WOW!  What a difference 24 hours makes.  Although I wasn’t too surprised as far as development, but am somewhat taken by how quick the ramp up was, given everything I had looked at in analysis last night.  Enter into the MDR, Tropical Storm Danny!  Being development as a depression occurred at 36.5W, I do not know if the NHC will designate this a Cape Verde system, as it may have just missed the criteria of being within 600 of the islands.

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

Location: 10.9°N 37.5°W
Moving: W at 12 mph
Min pressure: 1008 mb/29.77 in
Max sustained: 40 mph

HURREVAC NHC DANNY TRACKING MAP
HURREVAC.DANNY

Danny looks rather impressive on satellite imagery this evening.  Banding has become much more pronounced over the past few hours, and an established outflow is noted.  I do believe I spoke of this yesterday evening, in that if last nights disturbance could continue with the trend, it could begin to establish an upper level anticyclone over itself.  This is also mentioned in the NHC Forecast Discussion.

TROPICAL STORM DANNY FLOATER SATELLITE LOOP IMAGES
avn0-laloDANNY

swir0-lalodanny

CATL SATELLITE LOOP IMAGERYavn-l

Danny is currently moving toward the west, or just north of west at 280 degrees according to the NHC.  This motion is due to the steering flow just to the north of the storm, and a small weakness in the subtropical ridge.  I have drawn a red circle in the satellite image where the weakness is noted, and is linked to the loop feature.  Just click on the graphic, and you can get an idea of the steering flow.

DVORAK SATELLITE IMAGE (CLICK TO ANIMATE)
bd-l

Based on my analysis of the current and forecast steering layers, and combined with information contained in the NHC Forecast Discussion, I expect this general motion to continue for at least the next 72-96 hours.  Thereafter, forecast track will depend on how strong Danny can become, and how quick the subtropical ridge may build back in north of the storm.  Based on information in the NHC Forecast Discussion, the ridge may build back according to the ECMWF, which leads to the NHC forecast track solution.  Given the fact the GFS did not initialize the system accurately today, this means the consensus models are off.  Based on this, I concur with the NHC forecast track.  This could change prior to the end of the forecast period, as the atmosphere is continually changing…but at this moment, the official track contained in the above tracking map looks good.

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

Again, Danny continues to become slowly better organized.  In fact, recent loop imagery indicates what may be a CDO, and colder cloud tops that appear to be starting to coalesce around the center of circulation.  NHC did indicate that microwave imagery indicated a well developed low and mid level structure.

The current wind shear map did indicate the upper level anticyclone feature over Danny, with very low shear values.

CIMSS WIND SHEAR
tccaptureshear

The latest wind shear forecast from the GFS, which has handled the shear forecast for Danny thus far, in an exemplary manner, indicates upper level winds should remain conducive for further slow development.  The hindrance may still be some slight dry air intrusion.  However, as I addressed last night, especially in some of the weather groups I am in,  with noting the rapid expansion of the moisture field yesterday evening, given that Danny has a well developed structure and is fairly compact, slight dry air intrusion should be able to be mixed out.  This would be the most likely reason for the slower development.

GFS WIND SHEAR 120 HOURS
850200shear20

Based on the premise of only a slight hindrance of dry air, and improving structure in satellite loop imagery, I look for Danny to become a hurricane during the next 36-48 hours.

Based on these forecast parameters, I have to concur with the NHC Intensity Forecast for a Category 2 hurricane near the end of the forecast period.  Looking into the shear forecast past that time becomes less accurate, however as Danny approaches the islands, the GFS is indicating around days 7 -8 that wind shear could relax to 10-15 knots in the eastern Caribbean, but with somewhat of a little less favorable outflow pattern.  Let’s hope the pattern can weaken Danny by then, as there is some high heat content in the Caribbean.

CURRENT OHC MAP
ohc_aQG3_latest_natl

All interests in the Windward and Leeward islands should closely monitor the progress of Danny during the next 5 days for any significant changes.  I will continue to monitor Danny during the next 72-96 hours for any significant forecast changes to the steering pattern and upper level pattern.  I will also be watching any subsequent tropical waves for signs of development, and an area near Bermuda, which has a slim chance at developing subtropical features.

Elsewhere, Tropical Storm formation is not expected during the next 7 days.

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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2 Responses to TROPICAL STORM DANNY FORECAST SYNOPSIS…ISSUED AUG. 18, 2015…9:25 P.M. EDT

  1. Mike doll says:

    Thanks for the update Storm. Looks like my cruise will interesting next week port canaveral to the ABC’s and the grand Turk leaving Friday !!!! I’ll pay attention and let the captain know what you say ( he should listen to an old salty BMC) lol

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