June 22, 2024

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SPECIAL TROPICAL WEATHER STATEMENT…ISSUED APR. 21, 2024…6:20 P.M. EDT

5 min read

Disclaimer:  This site is not affiliated with the National Hurricane Center, Hurricane Hunters, Storm Prediction Center, or National Weather Service.  ALL forecasts herein are the result of my analysis, (to which you will see me at times, insert excerpts from various agencies due to the nature of the importance of the information) and I am solely responsible for the content.  As ALWAYS, follow the National Hurricane Center, National Weather Service, and your local Emergency Management officials for emergency decisions.  In addition, this is strictly a FORECAST OFFICE.  I CANNOT make decisions regarding travel plans, etc.  My purpose, is to provide you the information, based solely on information I analyze, and the accuracy of the information at hand of the time of analysis, so you may make informed decisions.
(T. F. “Storm” Walsh)

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I will reiterate, my forecasts are based on the available information at the time of analysis, and are only as accurate as the information analyzed and the solutions provided.

Good evening everyone!
This special statement pertains mainly to commercial shipping, and possibly Bermuda if the system moves further south initially.  Though this should have no affect on the U. S., I thought it important for oceanic shipping and any yachtsmen sailing the open Atlantic.

In scanning over certain items regarding the Atlantic and tropics this morning, it was noted that the ECMWF EPS Cyclone Formation Probability model has woken up, and has the hots for an area of low pressure associated with a frontal boundary, forecast to move off the NC/Mid Atlantic coast.  This morning, the probability of cyclone formation was at 50% – 60%, (yesterday was 25% – 30%) and I figured as with an earlier system a few months ago it was predicting, probs. would go down and then be dropped.  However, this afternoon’s update indicates probabilities jumped up to 90% – 100% of a depression AND Tropical Storm.
ECMWF EPS CYCLONE FORMATION PROBABILITY 00Z 21 APR.ecmwf-bufr-conuswide-prob_td_1d-4003200
12Z 21 APR
eps_tropcyc_prob_20_atlantic_96
The area of low pressure is forecast to emerge into the Atlantic either late this evening, or early tomorrow morning.  This low is associated with the current frontal boundary seen in the NHC TAFB surface analysis and WPC 18Z surface map:
USA_12Z
90fwbg
Both the ECMWF and GFS indicate a well defined low pressure area, which is forecast to strengthen briefly, and then begin to weaken and dissipate as it moves quickly to the NE.
ECMWF AND GFS MSLP ANOMALY FORECAST
ecmwf-deterministic-exatl-mslp_norm_anom-1713700800-1713808800-1713981600-80

gfs-deterministic-exatl-mslp_norm_anom-1713700800-1713808800-1713981600-80
After careful and lengthy analysis, it appears the models may be picking up on a few items, which would tend to suggest the probability of the low transitioning, or trying to transition to sub-tropical status.  Initially, and for about the first 24 hours, SST’s will be warm enough to support a sub-tropical system.  As the system begins to move more to the NE, SST’s fall below the 23C threshold needed.  The system begins as deep cold core, based on thermal analysis from the Cyclone Phase Evolution information.  However, about halfway through its trek, it appears to transition, barely, to a shallow warm core low.  As it moves further into much colder waters, it transitions back to a deep cold core system.
ECMWF AND GFS CYCLONE PHASE EVOLUTION INFORMATION:
65.phase2

70.phase2
My take on this is, while I am not saying a STS will definitely develop, somewhat favorable conditions are briefly in the forecast, and the possibility does exist.  I believe the transition to possible warm core may initially begin with the 24 hour SST’s, however, I don’t believe this is enough for the transition.  I think what we may see is, the possibility of a warm seclusion, in that as the front moves offshore, the cold front of the frontal boundary could “fracture”, and the warm front portion could be absorbed, with warmer air becoming trapped in the center.  The graphics in the link are from a Norwegian cyclone, but same principal.
WARM SECLUSION ARTICLE/GRAPHICS LINK:
https://resources.eumetrain.org/data/5/569/warm_core_seclusion.htm

Both global models do indicate wind shear to relax to around 20 – 25 knots with a divergent pattern aloft.  Given this, the process for any strengthening of the low will remain baroclinic.
ECMWF AND GFS WIND SHEAR FORECAST
ecmwf-deterministic-exatl-shear_850v200-3949200
gfs-deterministic-exatl-shear_850v200-3927600
Surface winds near and away from the center could reach Tropical Storm force, and wave heights could reach 14 – 20 ft near the center, with wave heights 8 – 10 ft near the coast of Bermuda.
ECMWF SURFACE WINDS FORECAST (knots)
ecmwf-deterministic-exatl-wnd10m_stream-1713700800-1713808800-1713981600-40
ECMWF AND WAVEWATCH 3 SIGNIFICANT WAVE HEIGHTS FORECAST
ecmwf-wave-exatl-sig_height_wave_dir-1713700800-1713808800-1714046400-40
ww3-exatl-ww3_sig_wave_height_dir-1713700800-1713808800-1714046400-40
I will continue to monitor this and update if necessary.

You may direct any questions by contacting me personally, ANYTIME, at: twalsh22000@yahoo.com

Have a blessed evening!

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

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.

palmharborforecastcenter

2024-04-21 22:16:53

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